Monthly Archives: January 2017

robotic vacuum cleaner

A robotic vacuum cleaner, often called a robovac, is an autonomous robotic vacuum cleaner that has intelligent programming and a limited vacuum cleaning system. Some designs use spinning brushes to reach tight corners. Others combine a number of cleaning features (mopping, UV sterilization, etc.) simultaneous to vacuuming, thus rendering the machine into more than just a robot “vacuum” cleaner.

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A cleaning robot seen from below

File:Roomba video.ogv

Video of a Roomba operating

Long-exposure photo showing the path taken by a Roomba over 45 minutes

The first robot cleaner to be put into production was Electrolux Trilobite by the Swedish household and professional appliances manufacturer, Electrolux. In 1996, one of Electrolux’s first versions of the Trilobite vacuum was featured on the BBC‘s science program, Tomorrow’s World.[1]

In 2001, the British technology company Dyson built and demonstrated a robot vacuum known as the DC06. However, due to its high price, it was never released to the market.[2]

In 2002, the American advanced technology company, iRobot launched the Roomba floor vacuuming robot. Initially, iRobot decided to produce 15,000 units and 10,000 more units depending on the success of the launch. The Roomba immediately became a huge consumer sensation. By the Christmas season, iRobot produced 50,000 units to meet the holiday demand. After this success, major specialty retailers as well as more than 4,000 outlets such as Target, Kohl’s and Linens ‘n Things began to carry the Roomba.[3]

Since 2002, new variations of robotic vacuum cleaners have appeared in the market. For example, the Canadian bObsweep robotic vacuum that both mops and vacuums,[4] or the Neato Robotics XV-11 robotic vacuum, which uses laser-vision rather than the traditional ultrasound based models.[5]

In 2014, Dyson announced the release of its new robotic vacuum called Dyson 360 Eye, equipped with a 360 degree camera that is mounted on the top of the robot vacuum cleaner and is supposed to provide a better navigation than other brands. The robot vacuum was scheduled for a Japan-only release in spring 2015 with international launches to follow later in the year.[6] Moreover, Dyson announced that the 360 Eye has twice the suction of any other robot vacuum. The accuracy of this claim is doubtful however, since Dyson has been sued for similar claims on multiple occasions before. [7]

from wikipedia

air filter

A particulate air filter is a device composed of fibrous materials which removes solid particulates such as dust, pollen, mould, and bacteria from the air. Filters containing an absorbent or catalyst such as charcoal (carbon) may also remove odors and gaseous pollutants such as volatile organic compounds or ozone.[1] Air filters are used in applications where air quality is important, notably in building ventilation systems and in engines.

Some buildings, as well as aircraft and other human-made environments (e.g., satellites and space shuttles) use foam, pleated paper, or spun fiberglass filter elements. Another method, air ionisers, use fibers or elements with a static electric charge, which attract dust particles. The air intakes of internal combustion engines and air compressors tend to use either paper, foam, or cotton filters. Oil bath filters have fallen out of favor. The technology of air intake filters of gas turbines has improved significantly in recent years, due to improvements in the aerodynamics and fluid dynamics of the air-compressor part of the gas turbines.

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Automotive cabin air filters[edit]

The cabin air filter is typically a pleated-paper filter that is placed in the outside-air intake for the vehicle’s passenger compartment. Some of these filters are rectangular and similar in shape to the combustion air filter. Others are uniquely shaped to fit the available space of particular vehicles’ outside-air intakes.

The first automaker to include a disposable filter to clean the ventilation system was the Nash MotorsWeather Eye“, introduced in 1940.[2]

Being a relatively recent addition to automobile equipment, this filter is often overlooked, and can greatly reduce the effectiveness of the vehicle’s air conditioning and heating performance. Clogged or dirty cabin air filters can significantly reduce airflow from the cabin vents, as well as introduce allergens into the cabin air stream. The poor performance of these filters is obscured by manufacturers by not using the MERV rating system. Some people mistakenly believe that some of these are HEPA filters.

Internal combustion engine air filters[edit]

The combustion air filter prevents abrasive particulate matter from entering the engine’s cylinders, where it would cause mechanical wear and oil contamination.

Most fuel injected vehicles use a pleated paper filter element in the form of a flat panel. This filter is usually placed inside a plastic box connected to the throttle body with ductwork. Older vehicles that use carburetors or throttle body fuel injection typically use a cylindrical air filter, usually a few inches high and between 6 inches (150 mm) and 16 inches (410 mm) in diameter. This is positioned above the carburetor or throttle body, usually in a metal or plastic container which may incorporate ducting to provide cool and/or warm inlet air, and secured with a metal or plastic lid. The overall unit (filter and housing together) is called the air cleaner.


Main article: Filter paper

Pleated paper filter elements are the nearly exclusive choice for automobile engine air cleaners, because they are efficient, easy to service, and cost-effective. The “paper” term is somewhat misleading, as the filter media are considerably different from papers used for writing or packaging, etc. There is a persistent belief amongst tuners, fomented by advertising for aftermarket non-paper replacement filters, that paper filters flow poorly and thus restrict engine performance. In fact, as long as a pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application, such filters present only trivial restriction to flow until the filter has become significantly clogged with dirt. Construction equipment engines also use this.


Oil-wetted polyurethane foam elements are used in some aftermarket replacement automobile air filters. Foam was in the past widely used in air cleaners on small engines on lawnmowers and other power equipment, but automotive-type paper filter elements have largely supplanted oil-wetted foam in these applications. Foam filters are still commonly used on air compressors for air tools up to 5Hp. Depending on the grade and thickness of foam employed, an oil-wetted foam filter element can offer minimal airflow restriction or very high dirt capacity, the latter property making foam filters a popular choice in off-road rallying and other motorsport applications where high levels of dust will be encountered. Due to the way dust is captured on foam filters, large amounts may be trapped without measurable change in airflow restriction.


Oiled cotton gauze is employed in a growing number of aftermarket automotive air filters marketed as high-performance items. In the past, cotton gauze saw limited use in original-equipment automotive air filters. However, since the introduction of the Abarth SS versions, the Fiat subsidiary supplies cotton gauze air filters as OE filters.

Stainless steel[edit]

Stainless steel mesh is another example of medium which allow more air to pass through. Stainless steel mesh comes with different mesh counts, offering different filtration standards. In an extreme modified engine lacking in space for a cone based air filter, some will opt to install a simple stainless steel mesh over the turbo to ensure no particles enter the engine via the turbo.

Oil bath[edit]

An oil bath air cleaner consists of a sump containing a pool of oil, and an insert which is filled with fibre, mesh, foam, or another coarse filter media. When the cleaner is assembled, the media-containing body of the insert sits a short distance above the surface of the oil pool. The rim of the insert overlaps the rim of the sump. This arrangement forms a labyrinthine path through which the air must travel in a series of U-turns: up through the gap between the rims of the insert and the sump, down through the gap between the outer wall of the insert and the inner wall of the sump, and up through the filter media in the body of the insert. This U-turn takes the air at high velocity across the surface of the oil pool. Larger and heavier dust and dirt particles in the air cannot make the turn due to their inertia, so they fall into the oil and settle to the bottom of the base bowl. Lighter and smaller particles are trapped by the filtration media in the insert, which is wetted by oil droplets aspirated there into by normal airflow.

Oil bath air cleaners were very widely used in automotive and small engine applications until the widespread industry adoption of the paper filter in the early 1960s. Such cleaners are still used in off-road equipment where very high levels of dust are encountered, for oil bath air cleaners can sequester a great deal of dirt relative to their overall size without loss of filtration efficiency or airflow. However, the liquid oil makes cleaning and servicing such air cleaners messy and inconvenient, they must be relatively large to avoid excessive restriction at high airflow rates, and they tend to increase exhaust emissions of unburned hydrocarbons due to oil aspiration when used on spark-ignition engines.[citation needed]

Water bath[edit]

In the early 20th century (about 1900 to 1930), water bath air cleaners were used in some applications (cars, trucks, tractors, and portable and stationary engines). They worked on roughly the same principles as oil bath air cleaners. For example, the original Fordson tractor had a water bath air cleaner. By the 1940s, oil bath designs had displaced water bath designs because of better filtering performance.

HVAC Air Filters[edit]

Filter classes[edit]

European Normalisation standards recognise the following filter classes:

Usage Class Performance Performance test Particulate size
approaching 100% retention
Test Standard
Coarse filters(used as


G1 65% Average value >5 µm BS EN779
G2 65–80% Average value >5 µm BS EN779
G3 80–90% Average value >5 µm BS EN779
G4 90%– Average value >5 µm BS EN779
Fine filters(used as


M5 40–60% Average value >5 µm BS EN779
M6 60–80% Average value >2 µm BS EN779
F7 80–90% Average value >2 µm BS EN779
F8 90–95% Average value >1 µm BS EN779
F9 95%– Average value >1 µm BS EN779
Semi HEPA E10 85% Minimum value >1 µm BS EN1822
E11 95% Minimum value >0.5 µm BS EN1822
E12 99.5% Minimum value >0.5 µm BS EN1822
HEPA H13 99.95% Minimum value >0.3 µm BS EN1822
H14 99.995% Minimum value >0.3 µm BS EN1822
ULPA U15 99.9995% Minimum value >0.3 µm BS EN1822
U16 99.99995% Minimum value >0.3 µm BS EN1822
U17 99.999995% Minimum value >0.3 µm BS EN1822

from wikipedia

air purifier

An air purifier is a device which removes contaminants from the air in a room. These devices are commonly marketed as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating second-hand tobacco smoke. The commercially graded air purifiers are manufactured as either small stand-alone units or larger units that can be affixed to an air handler unit (AHU) or to an HVAC unit found in the medical, industrial, and commercial industries. Air purifiers may also be used in industry to remove impurities such as CO2 from air before processing. Pressure swing adsorbers or other adsorption techniques are typically used for this.

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Use and benefits of purifiers[edit]

Dust, pollen, pet dander, mold spores, and dust mite feces can act as allergens, triggering allergies in sensitive people. Smoke particles and volatile organic compounds (VOCs) can pose a risk to health. Exposure to various components such as VOCs increases the likelihood of experiencing symptoms of sick building syndrome.[1] Air purifiers are becoming increasingly capable of capturing a greater number of bacterial, virus, and DNA damaging particulates.[citation needed]

Purifying techniques[edit]

Several different processes of varying effectiveness can be used to purify air.

  • Thermodynamic sterilization (TSS) – This technology uses heat sterilization via a ceramic core with micro capillaries, which are heated to 200 °C (392 °F). It is claimed that 99.9% of microbiological particles – bacteria, viruses, dust mite allergens, mold and fungus spores – are incinerated.[2] The air passes through the ceramic core by the natural process of air convection, and is then cooled using heat transfer plates and released. TSS is not a filtering technology, as it does not trap or remove particles.[3] TSS is claimed not to emit harmful by-products (although the byproducts of partial thermal decomposition are not addressed) and also reduces the concentration of ozone in the atmosphere.[4]
  • Ultraviolet germicidal irradiation – UVGI can be used to sterilize air that passes UV lamps via forced air. Air purification UVGI systems can be freestanding units with shielded UV lamps that use a fan to force air past the UV light. Other systems are installed in forced air systems so that the circulation for the premises moves micro-organisms past the lamps. Key to this form of sterilization is placement of the UV lamps and a good filtration system to remove the dead micro-organisms. For example, forced air systems by design impede line-of-sight, thus creating areas of the environment that will be shaded from the UV light. However, a UV lamp placed at the coils and drainpan of cooling system will keep micro-organisms from forming in these naturally damp places. The most effective method for treating the air rather than the coils is in-line duct systems, these systems are placed in the center of the duct and parallel to the air flow.
  • Filter – based purification traps airborne particles by size exclusion. Air is forced through a filter and particles are physically captured by the filter.
High-efficiency particulate arrestance (HEPA) filters remove at most 99.97% of 0.3-micrometer particles and are usually more effective at removing larger particles. HEPA purifiers, which filter all the air going into a clean room, must be arranged so that no air bypasses the HEPA filter. In dusty environments, a HEPA filter may follow an easily cleaned conventional filter (prefilter) which removes coarser impurities so that the HEPA filter needs cleaning or replacing less frequently. HEPA filters do not generate ozone or harmful byproducts in course of operation.
Filter HVAC at MERV 14 or above are rated to remove airborne particles of 0.3 micrometers or larger. A high efficiency MERV 14 filter has a capture rate of at least 75% for particles between 0.3 to 1.0 micrometers. Although the capture rate of a MERV filter is lower than that of a HEPA filter, a central air system can move significantly more air in the same period of time. Using a high-grade MERV filter can be more effective than using a high-powered HEPA machine at a fraction of the initial capital expenditure. Unfortunately, most furnace filters are slid in place without an airtight seal, which allows air to pass around the filters. This problem is worse for the higher-efficiency MERV filters because of the increase in air resistance. Higher-efficiency MERV filters are usually denser and increase air resistance in the central system, requiring a greater air pressure drop and consequently increasing energy costs.
  • Activated carbon is a porous material that can adsorb volatile chemicals on a molecular basis, but does not remove larger particles. The adsorption process when using activated carbon must reach equilibrium thus it may be difficult to completely remove contaminants.[5] Activated carbon is merely a process of changing contaminants from a gaseous phase to a solid phase, when aggravated or disturbed contaminants can be regenerated in indoor air sources.[6] Activated carbon can be used at room temperature and has a long history of commercial use. It is normally used in conjunction with other filter technology, especially with HEPA. Other materials can also absorb chemicals, but at higher cost.
  • Polarized-media electronic air cleaners use active electronically enhanced media to combine elements of both electronic air cleaners and passive mechanical filters. Most polarized-media electronic air cleaners convert 24-volt current to safe DC voltage to establish the polarized electric field. Airborne particles become polarized as they pass through the electric field and adhere to a disposable fiber media pad. Ultra-fine particles (UFPs) that are not collected on their initial pass through the media pad are polarized and agglomerate to other particles, odor and VOC molecules and are collected on subsequent passes. The efficiency of polarized-media electronic air cleaners increases as they load, providing high-efficiency filtration, with air resistance typically equal to or less than passive filters. Polarized-media technology is non-ionizing, which means no ozone is produced.
  • Photocatalytic oxidation (PCO) is an emerging technology in the HVAC industry.[7] In addition to the prospect of Indoor Air Quality (IAQ) benefits, it has the added potential for limiting the introduction of unconditioned air to the building space, thereby presenting an opportunity to achieve energy savings over previous prescriptive designs. As of May 2009[8][9] there was no more disputable concern raised by the Lawrence Berkeley National Laboratory data that PCO may significantly increase the amount of formaldehyde in real indoor environments.[10] As with other advanced technologies, sound engineering principles and practices should be employed by the HVAC designer to ensure proper application of the technology. Photocatalytic oxidation systems are able to completely oxidize and degrade organic contaminants. For example, Volatile Organic Compounds found low concentrations within a few hundred ppmv or less are the most likely to be completely oxidized.[5](PCO) uses short-wave ultraviolet light (UVC), commonly used for sterilization, to energize the catalyst (usually titanium dioxide (TiO2)[11]) and oxidize bacteria and viruses.[12] PCO in-duct units can be mounted to an existing forced-air HVAC system. PCO is not a filtering technology, as it does not trap or remove particles. It is sometimes coupled with other filtering technologies for air purification. UV sterilization bulbs must be replaced about once a year; manufacturers may require periodic replacement as a condition of warranty. Photocatalytic Oxidation systems often have high commercial costs.[5]
A related technology relevant to air purification is photoelectrochemical oxidation (PECO) Photoelectrochemical oxidation. While technically a type of PCO, PECO involves electrochemical interactions among the catalyst material and reactive species (e.g., through emplacement of cathodic materials) to improve quantum efficiency; in this way, it is possible to use lower energy UVA radiation as the light source and yet achieve improved effectiveness.[13]
  • Ionizer purifiers use charged electrical surfaces or needles to generate electrically charged air or gas ions. These ions attach to airborne particles which are then electrostatically attracted to a charged collector plate. This mechanism produces trace amounts of ozone and other oxidants as by-products.[1] Most ionizers produce less than 0.05 ppm of ozone, an industrial safety standard. There are two major subdivisions: the fanless ionizer and fan-based ionizer. Fanless ionizers are noiseless and use little power, but are less efficient at air purification. Fan-based ionizers clean and distribute air much faster. Permanently mounted home and industrial ionizer purifiers are called electrostatic precipitators.
  • Immobilized cell technology removes microfine particulate matter from the air by attracting charged particulates to a bio-reactive mass, or bioreactor, which enzymatically renders them inert.
  • Ozone generators are designed to produce ozone, and are sometimes sold as whole house air cleaners. Unlike ionizers, ozone generators are intended to produce significant amounts of ozone, a strong oxidant gas which can oxidize many other chemicals. The only safe use of ozone generators is in unoccupied rooms, utilising “shock treatment” commercial ozone generators that produce over 3000 mg of ozone per hour. Restoration contractors use these types of ozone generators to remove smoke odors after fire damage, musty smells after flooding, mold (including toxic molds), and the stench caused by decaying flesh which cannot be removed by bleach or anything else except for ozone. However, it is not healthy to breathe ozone gas, and one should use extreme caution when buying a room air purifier that also produces ozone.[14]
  • Titanium dioxide (TiO2) technology – nanoparticles of TiO2, together with calcium carbonate to neutralize any acidic gasses that may be adsorbed, is mixed into slightly porous paint. Photocatalysis initiates the decomposition of airborne contaminants at the surface.[15]

Consumer concerns[edit]

Other aspects of air cleaners are hazardous gaseous by-products, noise level, frequency of filter replacement, electrical consumption, and visual appeal. Ozone production is typical for air ionizing purifiers. Although high concentration of ozone is dangerous, most air ionizers produce low amounts (< 0.05 ppm). The noise level of a purifier can be obtained through a customer service department and is usually reported in decibels (dB). The noise levels for most purifiers are low compared to many other home appliances.[citation needed] Frequency of filter replacement and electrical consumption are the major operation costs for any purifier. There are many types of filters; some can be cleaned by water, by hand or by vacuum cleaner, while others need to be replaced every few months or years. In the United States, some purifiers are certified as Energy Star and are energy efficient.

HEPA technology is used in portable air purifiers as it removes common airborne allergens. The US Department of Energy has requirements manufacturers must pass to meet HEPA requirements. The HEPA specification requires removal of at least 99.97% of 0.3 micrometers airborne pollutants. Products that claim to be “HEPA-type”, “HEPA-like”, or “99% HEPA” do not satisfy these requirements and may not have been tested in independent laboratories.

Air purifiers may be rated on: CADR(Clean Air Delivery Rate); efficient area coverage; air changes per hour; the clean air delivery rate, which determines how well air has been purified; energy usage; and the cost of the replacement filters. Two other important factors to consider are the length that the filters are expected to last (measured in months or years) and the noise produced (measured in decibels) by the various settings that the purifier runs on. This information is available from most manufacturers.

Potential ozone hazards[edit]

As with other health-related appliances, there is controversy surrounding the claims of certain companies, especially involving ionic air purifiers. Many air purifiers generate some ozone, an energetic allotrope of three oxygen atoms, and in the presence of humidity, small amounts of NOx. Because of the nature of the ionization process, ionic air purifiers tend to generate the most ozone.[citation needed] This is a serious concern, because ozone is a criteria air pollutant regulated by health-related US federal and state standards. In a controlled experiment, in many cases, ozone concentrations were well in excess of public and/or industrial safety levels established by US Environmental Protection Agency, particularly in poorly ventilated rooms.[16]

Ozone can damage the lungs, causing chest pain, coughing, shortness of breath and throat irritation. It can also worsen chronic respiratory diseases such as asthma and compromise the ability of the body to fight respiratory infections—even in healthy people. People who have asthma and allergy are most prone to the adverse effects of high levels of ozone.[17] For example, increasing ozone concentrations to unsafe levels can increase the risk of asthma attacks.

Due to the below average performance and potential health risks, Consumer Reports has advised against using ozone producing air purifiers.[18] IQAir, the educational partner of the American Lung Association, has been a leading industry voice against ozone-producing air cleaning technology.[19]

Ozone generators used for shock treatments (unoccupied rooms) which are needed by smoke, mold, and odor remediation contractors as well as crime scene cleanup companies to oxidize and permanently remove smoke, mold, and odor damage are considered a valuable and effective tool when used correctly for commercial and industrial purposes. However, there is a growing body of evidence that these machines can produce undesirable by-products.[20]

In September 2007, the California Air Resources Board announced a ban of indoor air cleaning devices which produce ozone above a legal limit. This law, which took effect in 2010, requires testing and certification of all types of indoor air cleaning devices to verify that they do not emit excessive ozone.[21][22]

from wikipedia


Freeze-drying—technically known as lyophilisation, lyophilization, or cryodesiccation—is a dehydration process typically used to preserve a perishable material or make the material more convenient for transport. Freeze-drying works by freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to the gas phase.

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The process of freeze-drying was invented in 1906 by Arsène d’Arsonval and his assistant Frédéric Bordas at the laboratory of biophysics of Collège de France in Paris.[1][2] In 1911 Downey Harris and Shackle developed[3] the freeze-drying method of preserving live rabies virus which eventually led to development of the first antirabies vaccine.

Modern freeze-drying was developed during World War II. Blood serum being sent to Europe from the US for medical treatment of the wounded required refrigeration, but because of the lack of simultaneous refrigeration and transport, many serum supplies were spoiling before reaching their intended recipients. The freeze-drying process was developed as a commercial technique that enabled serum to be rendered chemically stable and viable without having to be refrigerated. Shortly thereafter, the freeze-dry process was applied to penicillin and bone, and lyophilization became recognized as an important technique for preservation of biologicals. Since that time, freeze-drying has been used as a preservation or processing technique for a wide variety of products. These applications include the following but are not limited to: the processing of food,[4] pharmaceuticals,[5] and diagnostic kits; the restoration of water damaged documents;[6] the preparation of river-bottom sludge for hydrocarbon analysis; the manufacturing of ceramics used in the semiconductor industry; the production of synthetic skin; the manufacture of sulfur-coated vials; and the restoration of historic/reclaimed boat hulls.


In a typical phase diagram, the boundary between gas and liquid runs from the triple point to the critical point. Freeze-drying (blue arrow) brings the system around the triple point, avoiding the direct liquid-gas transition seen in ordinary drying time (green arrow).

There are four stages in the complete drying process: pretreatment, freezing, primary drying, and secondary drying.


Pretreatment includes any method of treating the product prior to freezing. This may include concentrating the product, formulation revision (i.e., addition of components to increase stability, preserve appearance, and/or improve processing), decreasing a high-vapor-pressure solvent, or increasing the surface area. In many instances the decision to pretreat a product is based on theoretical knowledge of freeze-drying and its requirements, or is demanded by cycle time or product quality considerations.[7]


In a lab, this is often done by placing the material in a freeze-drying flask and rotating the flask in a bath, called a shell freezer, which is cooled by mechanical refrigeration, dry ice in aqueous methanol, or liquid nitrogen. On a larger scale, freezing is usually done using a freeze-drying machine. In this step, it is important to cool the material below its triple point, the lowest temperature at which the solid and liquid phases of the material can coexist. This ensures that sublimation rather than melting will occur in the following steps. Larger crystals are easier to freeze-dry. To produce larger crystals, the product should be frozen slowly or can be cycled up and down in temperature. This cycling process is called annealing. However, in the case of food, or objects with formerly-living cells, large ice crystals will break the cell walls (a problem discovered, and solved, by Clarence Birdseye), resulting in the destruction of more cells, which can result in increasingly poor texture and nutritive content. In this case, the freezing is done rapidly, in order to lower the material to below its eutectic point quickly, thus avoiding the formation of ice crystals. Usually, the freezing temperatures are between −50 °C and −80 °C (-58 °F and -112 °F) . The freezing phase is the most critical in the whole freeze-drying process, because the product can be spoiled if improperly done.

Amorphous materials do not have a eutectic point, but they do have a critical point, below which the product must be maintained to prevent melt-back or collapse during primary and secondary drying.

Primary drying[edit]

During the primary drying phase, the pressure is lowered (to the range of a few millibars), and enough heat is supplied to the material for the ice to sublime. The amount of heat necessary can be calculated using the sublimating molecules’ latent heat of sublimation. In this initial drying phase, about 95% of the water in the material is sublimated. This phase may be slow (can be several days in the industry), because, if too much heat is added, the material’s structure could be altered.

In this phase, pressure is controlled through the application of partial vacuum. The vacuum speeds up the sublimation, making it useful as a deliberate drying process. Furthermore, a cold condenser chamber and/or condenser plates provide a surface(s) for the water vapour to re-solidify on. This condenser plays no role in keeping the material frozen; rather, it prevents water vapor from reaching the vacuum pump, which could degrade the pump’s performance. Condenser temperatures are typically below −50 °C (−58 °F).

It is important to note that, in this range of pressure, the heat is brought mainly by conduction or radiation; the convection effect is negligible, due to the low air density.

Secondary drying[edit]

The secondary drying phase aims to remove unfrozen water molecules, since the ice was removed in the primary drying phase. This part of the freeze-drying process is governed by the material’s adsorption isotherms. In this phase, the temperature is raised higher than in the primary drying phase, and can even be above 0 °C, to break any physico-chemical interactions that have formed between the water molecules and the frozen material. Usually the pressure is also lowered in this stage to encourage desorption (typically in the range of microbars, or fractions of a pascal). However, there are products that benefit from increased pressure as well.

After the freeze-drying process is complete, the vacuum is usually broken with an inert gas, such as nitrogen, before the material is sealed.

At the end of the operation, the final residual water content in the product is extremely low, around 1% to 4%.

Properties of freeze-dried products[edit]

If a freeze-dried substance is sealed to prevent the reabsorption of moisture, the substance may be stored at room temperature without refrigeration, and be protected against spoilage for many years. Preservation is possible because the greatly reduced water content inhibits the action of microorganisms and enzymes that would normally spoil or degrade the substance.

Freeze-drying also causes less damage to the substance than other dehydration methods using higher temperatures. Freeze-drying does not usually cause shrinkage or toughening of the material being dried. In addition, flavours, smells and nutritional content generally remain unchanged, making the process popular for preserving food. However, water is not the only chemical capable of sublimation, and the loss of other volatile compounds such as acetic acid (vinegar) and alcohols can yield undesirable results.

Freeze-dried products can be rehydrated (reconstituted) much more quickly and easily because the process leaves microscopic pores. The pores are created by the ice crystals that sublimate, leaving gaps or pores in their place. This is especially important when it comes to pharmaceutical uses. Freeze-drying can also be used to increase the shelf life of some pharmaceuticals for many years.


Similar to cryoprotectants, some molecules protect freeze-dried material. Known as lyoprotectants, these molecules are typically polyhydroxy compounds such as sugars (mono-, di-, and polysaccharides), polyalcohols, and their derivatives. Trehalose and sucrose are natural lyoprotectants. Trehalose is produced by a variety of plant (for example selaginella and arabidopsis thaliana), fungi, and invertebrate animals that remain in a state of suspended animation during periods of drought (also known as anhydrobiosis).


Pharmaceutical and biotechnology[edit]

Lyophilized 5% w/v sucrose cake in a pharmaceutical glass vial

Pharmaceutical companies often use freeze-drying to increase the shelf life of the products, such as live virus vaccines,[8] biologics[9] and other injectables. By removing the water from the material and sealing the material in a glass vial, the material can be easily stored, shipped, and later reconstituted to its original form for injection. Another example from the pharmaceutical industry is the use of freeze drying to produce tablets or wafers, the advantage of which is less excipient as well as a rapidly absorbed and easily administered dosage form.

Freeze-dried pharmaceutical products are produced as lyophilized powders for reconstitution in vials and more recently in prefilled syringes for self-administration by a patient. Many biopharmaceutical products based on therapeutic proteins such as monoclonal antibodies require lyophilization for stability. Examples of lyophilized biopharmaceuticals include blockbuster drugs such as Etanercept (Enbrel by Pfizer), Infliximab (Remicade by Janssen Biotech), Rituximab and Trastuzumab (Herceptin by Genentech).

Freeze-drying is also used in manufacturing of raw materials for pharmaceutical products. Active Pharmaceutical Product Ingredients (APIs) are lyophilized to achieve chemical stability under room temperature storage. Bulk lyophilization of APIs is typically conducted using trays instead of glass vials.

Dry powders of probiotics are often produced by bulk freeze-drying of live microorganisms such as Lactic acid bacteria and Bifidobacteria.[10]

Food and agriculture-based industries[edit]

Freeze dried bacon bars

Freeze-dried coffee, a form of instant coffee

Although freeze-drying is used to preserve food, its earliest use in agriculturally based industries was in processing of crops such as peanuts/groundnuts and tobacco in the early 1970s. Because heat, commonly used in crop and food processing, invariably alters the structure and chemistry of the product, the main objective of freeze-drying is to avoid heat and thus preserve the structural and chemical integrity/composition with little or no alteration.[11] Therefore, freeze-dried crops and foods are closest to the natural composition with respect to structure and chemistry. The process came to wide public attention when it was used to create freeze-dried ice cream, an example of astronaut food. It is also widely used to produce essences or flavourings to add to food.

Because of its light weight per volume of reconstituted food, freeze-dried products are popular and convenient for hikers. More dried food can be carried per the same weight of wet food, and remains in good condition for longer than wet food, which tends to spoil quickly. Hikers reconstitute the food with water available at point of use.

Instant coffee is sometimes freeze-dried, despite the high costs of the freeze-driers used. The coffee is often dried by vaporization in a hot air flow, or by projection onto hot metallic plates. Freeze-dried fruits are used in some breakfast cereal or sold as a snack, and are an especially popular snack choice among toddlers, preschoolers, hikers and dieters, as well as being used by some pet owners as a treat for pet birds. Most commercial freezing is done either in cold air kept in motion by fans (blast freezing) or by placing the foodstuffs in packages or metal trays on refrigerated surfaces (contact freezing).

Culinary herbs, vegetables (such as vitamin-rich spinach and watercress), the temperature sensitive baker`s yeast suspension and the nutrient-rich pre-boiled rice can also be freeze-dried. During three hours of drying the spinach and watercress has lost over 98% of its water content, followed by the yeast suspension with 96% and the pre-boiled rice by 75%.[12] The air-dried herbs are far more common and less expensive. Freeze dried tofu is a popular foodstuff in Japan (“Koya-dofu” or “shimi-dofu” in Japanese).

Technological industry[edit]

In chemical synthesis, products are often freeze-dried to make them more stable, or easier to dissolve in water for subsequent use.

In bioseparations, freeze-drying can be used also as a late-stage purification procedure, because it can effectively remove solvents. Furthermore, it is capable of concentrating substances with low molecular weights that are too small to be removed by a filtration membrane. Freeze-drying is a relatively expensive process. The equipment is about three times as expensive as the equipment used for other separation processes, and the high energy demands lead to high energy costs. Furthermore, freeze-drying also has a long process time, because the addition of too much heat to the material can cause melting or structural deformations. Therefore, freeze-drying is often reserved for materials that are heat-sensitive, such as proteins, enzymes, microorganisms, and blood plasma. The low operating temperature of the process leads to minimal damage of these heat-sensitive products.

In nanotechnology, freeze-drying is used for nanotube purification[13] to avoid aggregation due to capillary forces during regular thermal vaporization drying.

Other uses[edit]

Organizations such as the Document Conservation Laboratory at the United States National Archives and Records Administration (NARA) have done studies on freeze-drying as a recovery method of water-damaged books and documents. While recovery is possible, restoration quality depends on the material of the documents. If a document is made of a variety of materials, which have different absorption properties, expansion will occur at a non-uniform rate, which could lead to deformations. Water can also cause mold to grow or make inks bleed. In these cases, freeze-drying may not be an effective restoration method.

In bacteriology freeze-drying is used to conserve special strains.

In high-altitude environments, the low temperatures and pressures can sometimes produce natural mummies by a process of freeze-drying.

Advanced ceramics processes sometimes use freeze-drying to create a formable powder from a sprayed slurry mist. Freeze-drying creates softer particles with a more homogeneous chemical composition than traditional hot spray drying, but it is also more expensive.

Freeze-drying is also used for floral preservation. Wedding bouquet preservation has become very popular with brides who want to preserve their wedding day flowers[14]

A new form of burial which previously freeze-dries the body with liquid nitrogen has been developed by the Swedish company Promessa Organic AB, which puts it forward as an environmentally friendly alternative to traditional casket and cremation burials.


Unloading trays of freeze-dried material from a small cabinet-type freeze-dryer

There are essentially three categories of freeze-dryers: the manifold freeze-dryer, the rotary freeze-dryer and the tray style freeze-dryer. Two components are common to all types of freeze-dryers: a vacuum pump to reduce the ambient gas pressure in a vessel containing the substance to be dried and a condenser to remove the moisture by condensation on a surface cooled to −40 to −80 °C (−40 to −112 °F). The manifold, rotary and tray type freeze-dryers differ in the method by which the dried substance is interfaced with a condenser. In manifold freeze-dryers a short usually circular tube is used to connect multiple containers with the dried product to a condenser. The rotary and tray freeze-dryers have a single large reservoir for the dried substance.

Rotary freeze-dryers are usually used for drying pellets, cubes and other pourable substances. The rotary dryers have a cylindrical reservoir that is rotated during drying to achieve a more uniform drying throughout the substance. Tray style freeze-dryers usually have rectangular reservoir with shelves on which products, such as pharmaceutical solutions and tissue extracts, can be placed in trays, vials and other containers.

Manifold freeze-dryers are usually used in a laboratory setting when drying liquid substances in small containers and when the product will be used in a short period of time. A manifold dryer will dry the product to less than 5% moisture content. Without heat, only primary drying (removal of the unbound water) can be achieved. A heater must be added for secondary drying, which will remove the bound water and will produce a lower moisture content.

Tray style freeze-dryers are typically larger than the manifold dryers and are more sophisticated. Tray style freeze-dryers are used to dry a variety of materials. A tray freeze-dryer is used to produce the driest product for long-term storage. A tray freeze-dryer allows the product to be frozen in place and performs both primary (unbound water removal) and secondary (bound water removal) freeze-drying, thus producing the driest possible end-product. Tray freeze-dryers can dry products in bulk or in vials or other containers. When drying in vials, the freeze-dryer is supplied with a stoppering mechanism that allows a stopper to be pressed into place, sealing the vial before it is exposed to the atmosphere. This is used for long-term storage, such as vaccines.

Improved freeze-drying techniques are being developed to extend the range of products that can be freeze-dried, to improve the quality of the product, and to produce the product faster with less labor.

In popular culture[edit]

1986 movie SpaceCamp made freeze-dried ice cream a popular snack in the United States.

from wikipedia

Vacuum packing

Vacuum packing is a method of packaging that removes air from the package prior to sealing. This method involves (manually or automatically) placing items in a plastic film package, removing air from inside, and sealing the package.[1]Shrink film is sometimes used to have a tight fit to the contents. The intent of vacuum packing is usually to remove oxygen from the container to extend the shelf life of foods and, with flexible package forms, to reduce the volume of the contents and package.[2]

Vacuum packing reduces atmospheric oxygen, limiting the growth of aerobic bacteria or fungi, and preventing the evaporation of volatile components. It is also commonly used to store dry foods over a long period of time, such as cereals, nuts, cured meats, cheese, smoked fish, coffee, and potato chips (crisps). On a more short term basis, vacuum packing can also be used to store fresh foods, such as vegetables, meats, and liquids, because it inhibits bacterial growth.

Vacuum packing greatly reduces the bulk of non-food items. For example, clothing and bedding can be stored in bags evacuated with a domestic vacuum cleaner or a dedicated vacuum sealer. This technique is sometimes used to compact household waste, for example where a charge is made for each full bag collected.

Vacuum packaging products, using plastic bags, canisters, bottles, or mason jars, are available for home use.

For delicate food items which might be crushed by the vacuum packing process (such as potato chips), an alternative is to replace the interior gas with nitrogen. This has the same effect of inhibiting deterioration due to the removal of oxygen.

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External sealers[edit]

External vacuum sealers involve a bag being attached to the vacuum-sealing machine externally. The machine will remove the air and seal the bag, which is all done outside the machine. A heat sealer is often used to seal the pack.

Single Vacuum Chamber Machines[edit]

File:Vacuum Packaging Machine.webm

This video shows vacuum packaging of organic rice.

Tabletop Vacuum Packaging Machine

Single chamber sealers require the entire product to be placed within the machine. Like external sealers, a plastic bag is typically used for packaging. Once the product is placed in the machine, the lid is closed and air is removed. Then, there is a heat seal inside the chamber that will seal the bag, after sealing the bag the chamber is refilled with air by the automatic opening of a vent to the outside. This oncoming pressure squeezes all remaining air in the bag. The lid is then opened and the product removed. Chamber sealers are typically used for low-to-medium-volume packaging, and also have the capability to vacuum seal liquids.

Double Vacuum Chamber Machines[edit]

Double Chamber Vacuum Packaging Machine

Double chamber sealers require the entire product to be placed in a plastic bag within the machine. Once the product is placed in the machine on the seal bar, the lid is closed and air is removed. Then a seal bar inside the chamber seals the product in the bag, after sealing the bag the chamber is refilled with air by the automatic opening of a vent to the outside. This oncoming pressure squeezes all remaining air in the bag. The lid is then opened and the product removed. Double chamber sealers are typically used for medium-volume packaging, and also have the capability to vacuum seal liquids. The lid generally swings from one side to another, increasing production speed over a single chamber model. Double chamber vacuum packaging machines generally have either spring-weighted lids or fully automatic lids.

Double chamber vacuum packaging machines are commonly used for:

  • Fresh Meat
  • Processed Meat
  • Cheese (hard and soft)
  • Candy & Chocolate
  • Empty Cans (it’s a example of atmospheric pressure)

Automatic Belt Vacuum Chamber Machines[edit]

Automatic Belt Vacuum Chamber Machine. Automatic belt vacuum chamber machines offer vastly increased speed and automation and accommodate large products.

Automatic belt chamber sealers require the entire product to be placed in a plastic bag or flow wrapped pouch within the machine. The product travels on the conveyor belt, it is automatically positioned in the machine on the seal bar, the lid is closed and air is removed. Then a seal bar inside the chamber seals the product in the bag. After sealing the bag, the chamber is refilled with air by the automatic opening of a vent to the outside. This oncoming pressure squeezes all remaining air in the bag. The lid is then opened and the product removed. Automatic belt vacuum chamber machines are typically used for high-speed packaging of large items, and also have the capability to vacuum seal liquids. The lid generally travels straight up and down.

Automatic belt vacuum chamber packaging machines are commonly used for:

  • Fresh Meat (large portions)
  • Processed Meat
  • Large Sausage logs
  • Cheese (hard and soft)

Thermoforming (rollstock) Vacuum Packaging Machines[edit]

Thermoform packaging machines are used in larger production facilities for vacuum packaging products.

Vacuum Packaging in large production facilities can be done with thermoforming machines. These are Form-Fill-Seal style machines that form the package from rolls of packaging film (webbing). Products are loaded into the thermoformed pockets, the top web is laid and sealed under a vacuum, producing vacuum packaged products. Thermoforming can greatly increase packaging production speed. Thermoformed plastics can be customized for size, color, clarity, and shape to fit products perfectly, creating a consistent appearance. Some common uses for Thermoforming in vacuum packaging include:

  • Fresh & Marinated Meat
  • Sausage
  • Cheese
  • Candy / Chocolate
  • Grain
  • Grab-and-Go Snacks (beef jerky, snack sticks)
  • Pharmaceutical and Medical Products
  • Coins / Collectables

Shelf life[edit]

Depending on the product, the shelf life of vacuum packaged products can exceed normal bagged or wrapped packages. Beef can last up to six weeks refrigerated, and much longer when frozen.[citation needed]

High Barrier Shrink Vacuum Bags[edit]

The amount of shelf life enhanced by a vacuum bag is dependent on the structure in the material. A standard vacuum bag is composed of a PA/PE structure where PA is for puncture resistance and PE is for sealing. The high barrier category includes the usage of more layers focused on the prevention of oxygen permeability, and therefore shelf life protection. There are two materials used in high barrier structures, polyvinylidene chloride (PVDC) and ethylene vinyl alcohol (EVOH). Shelf life indication can be effectively measured by how many cubic centimeters of oxygen can permeate through 1 square meter of material over a 24-hour period. A standard PA/PE bag allows on average 100 cubic centimeters, PVDC allows on average over 10, and EVOH on average 1 cubic centimeter. Multi-layer structures allow the ability to use strong oxygen-barrier materials for enhanced shelf life protection. The PremiumPack structure is a good example of EVOH based high barrier shrink material.

Preventing freezer burn[edit]

When foods are frozen without preparation, freezer burn can occur. It happens when the surface of the food is dehydrated, and this leads to a dried and leathery appearance. Freezer burn also ruins the flavor and texture of foods. Vacuum packing reduces freezer burn by preventing the food from exposure to the cold, dry air.

Sous-vide cooking[edit]

Vacuum packaging also allows for a special cooking method, sous-vide. Sous-vide, French for under vacuum, involves poaching food that is vacuum sealed in a plastic bag.

Food safety[edit]

In an oxygen-depleted environment, anaerobic bacteria can proliferate, potentially causing food-safety issues. Vacuum packing is often used in combination with other packaging and food processing techniques.

from wikipedia

Freezer burn

Freezer burn is a condition that occurs when frozen food has been damaged by dehydration and oxidation, due to air reaching the food.[1] It is generally caused by food not being securely wrapped in air-tight packaging.

Freezer burn appears as grayish-brown leathery spots on frozen food, and occurs when air reaches the food’s surface and dries the product. Color changes result from chemical changes in the food’s pigment. Freezer burn does not make the food unsafe; it merely causes dry spots in foods.[2] Provided that the freezer burns are removed before cooking, the food remains usable and edible.

Cause and effects[edit]

The condition is primarily caused by sublimation. Water evaporates at all temperatures, even from the surface of solid ice. If air adjacent to ice is cold enough and the air is dry enough, the ice does not melt and water molecules go directly from solid phase (ice) to gaseous phase (vapor) without going through a liquid phase. When the constantly vibrating water molecules in foods stored in a freezer migrate to the surface, crystals of ice outside of the solid food are formed, and some water molecules escape into the air by sublimation. The parts of meat which are deprived of moisture become dry and shrivelled, appearing “burnt”. In meats, air can cause fats to oxidize.

This process occurs even if the package has never been opened, due to the tendency for all molecules, especially water, to escape solids via vapour pressure. Fluctuations in temperature within a freezer also contribute to the onset of freezer burn because such fluctuations set up temperature gradients within the solid food and air in the freezer, which create additional impetus for water molecules to move from their original positions.

It is possible to slow freezer burn by filling plastic containers with water and leaving them open (leaving room for expansion) in the freezer to help maintain humidity. Proper packaging can also help delay freezer burn because small, air-tight packaging allows local homeostasis of humidity, and, to a lesser degree, temperature, although current available packaging cannot do this perfectly.

Meats and vegetables stored in a manual-defrost freezer will last longer than those stored in automatic-defrost freezers. This is because the temperature of a manual defrost freezer remains closer to −18 °C (0 °F) while the temperature of automatic defrost freezers fluctuates, and because automatic-defrost freezers have drier air, thus the rate of sublimation increases.

Food with freezer burn, though dried and wrinkled, is safe to eat. However, food afflicted with freezer burn may have an unpleasant flavour. In most cases, it is sufficient to remove the parts affected by freezer burn.

from wikipedia


A foam is a substance that is formed by trapping pockets of gas in a liquid or solid.[1] A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas.

An important division of solid foams is into closed-cell foams and open-cell foams. In a closed-cell foam, the gas forms discrete pockets, each completely surrounded by the solid material. In an open-cell foam, the gas pockets connect with each other. A bath sponge is an example of an open-cell foam: water can easily flow through the entire structure, displacing the air. A camping mat is an example of a closed-cell foam: the gas pockets are sealed from each other so the mat cannot soak up water.

Foams are examples of dispersed media. In general, gas is present in large amount so it will be divided into gas bubbles of many different sizes (the material is polydisperse) separated by liquid regions which may form films, thinner and thinner when the liquid phase is drained out of the system films.[2] When the principal scale is small, i.e. for a very fine foam, this dispersed medium can be considered as a type of colloid.

The term foam may also refer to anything that is analogous to such a foam, such as quantum foam, polyurethane foam (foam rubber), XPS foam, polystyrene, phenolic, or many other manufactured foams.

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A foam is in many cases a multiscale system.

Order and disorder of bubbles in a surface foam.

One scale is the bubble: material foams are typically disordered and have a variety of bubble sizes. At larger sizes, the study of idealized foams is closely linked to the mathematical problems of minimal surfaces and three-dimensional tessellations, also called honeycombs. The Weaire–Phelan structure is believed to be the best possible (optimal) unit cell of a perfectly ordered foam,[3] while Plateau’s laws describe how soap-films form structures in foams.

At lower scale than the bubble is the thickness of the film for metastable foams, which can be considered as a network of interconnected films called lamellae. Ideally, the lamellae are connected in triads and radiate 120° outward from the connection points, known as Plateau borders.

An even lower scale is the liquid–air interface at the surface of the film. Most of the time this interface is stabilized by a layer of amphiphilic structure, often made of surfactants, particles (Pickering emulsion), or more complex associations.


Several conditions are needed to produce foam: there must be mechanical work, surface active components (surfactants) that reduce the surface tension, and the formation of foam faster than its breakdown. To create foam, work (W) is needed to increase the surface area (ΔA):

{\displaystyle W=\gamma \Delta A\,\!} W = \gamma \Delta A \,\!

where γ is the surface tension.

One of the ways foam is created is through dispersion, where a large amount of gas is mixed with a liquid. A more specific method of dispersion involves injecting a gas through a hole in a solid into a liquid. If this process is completed very slowly, then one bubble can be emitted from the orifice at a time as shown in the picture below.

One of the theories put forth for determining the separation time is shown below; however, while this theory produces the theoretical data that matches with experimental data, detachment due to capillarity is accepted as a better explanation.

Rising bubble from orifice

The buoyancy force will act to raise the bubble, which is

{\displaystyle F_{b}=Vg(\rho _{2}-\rho _{1})\!} F_b = Vg(\rho_2-\rho_1)\!

where {\displaystyle V}V is the volume of the bubble, {\displaystyle g}g is the acceleration due to gravity, and ρ1 is the density of the gas ρ2 is the density of the liquid. The force working against the buoyancy force is the surface tension force, which is

{\displaystyle F_{s}=2r\pi \gamma \!} F_s = 2r \pi\gamma\!,

where γ is the surface tension, and {\displaystyle r}r is the radius of the orifice. As more air is pushed into the bubble, the buoyancy force grows quicker than the surface tension force. Thus, detachment will occur when the buoyancy force is large enough to overcome the surface tension force.

{\displaystyle Vg(\rho _{2}-\rho _{1})>2r\pi \gamma \!} Vg(\rho_2-\rho_1)> 2r \pi\gamma\!

In addition, if the bubble is treated as a sphere with a radius of {\displaystyle R}R and the volume {\displaystyle V}V is substituted in to the equation above, separation occurs at the moment when

{\displaystyle R^{3}={\frac {3r\gamma }{2g(\rho _{2}-\rho _{1})}}\!} R^3=\frac{3r\gamma}{2g(\rho_2-\rho_1)}\!

Examining this phenomenon from a capillarity viewpoint for a bubble that is being formed very slowly, it can be assumed that the pressure {\displaystyle p}p inside is constant everywhere. The hydrostatic pressure in the liquid is designated by {\displaystyle p_{0}}p_{0}. The change in pressure across the interface from gas to liquid is equal to the capillary pressure; hence,

{\displaystyle p-p_{0}=\gamma \left({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}\right)\!} p-p_0=\gamma\left (\frac{1}{R_1}+\frac{1}{R_2}\right)\!

where R1 and R2 are the radii of curvature and are set as positive. At the stem of the bubble, R3 and R4 are the radii of curvature also treated as positive. Here the hydrostatic pressure in the liquid has to take in account z, the distance from the top to the stem of the bubble. The new hydrostatic pressure at the stem of the bubble is p0(ρ1 − ρ2)z. The hydrostatic pressure balances the capillary pressure which is shown below:

{\displaystyle p-p_{0}-(\rho _{2}-\rho _{1})gz=\gamma \left({\frac {1}{R_{3}}}+{\frac {1}{R_{4}}}\right)\!} p-p_0-(\rho_2-\rho_1)gz=\gamma\left (\frac{1}{R_3}+\frac{1}{R_4}\right)\!

Finally, the difference in the top and bottom pressure will equal the change in hydrostatic pressure:

{\displaystyle (\rho _{2}-\rho _{1})gz=\gamma \left({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}-{\frac {1}{R_{3}}}-{\frac {1}{R_{4}}}\right)\!}{\displaystyle (\rho _{2}-\rho _{1})gz=\gamma \left({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}-{\frac {1}{R_{3}}}-{\frac {1}{R_{4}}}\right)\!}

At the stem of the bubble, the shape of the bubble is nearly cylindrical; consequently, either R3 or R4 will be very large while the other radius of curvature will be very small. As the stem of the bubble grows in length, it becomes more unstable as one of the radius grows and the other shrinks. At a certain point, the vertical length of the stem exceeds the circumference of the stem and due to the buoyancy forces the bubble separates and the process repeats.[4]



Marangoni effect of a film

Marangoni effect of a film (2)

Stabilization of foam is caused by van der Waals forces between the molecules in the foam, electrical double layers created by dipolar surfactants, and the Marangoni effect, which acts as a restoring force to the lamellae.

The Marangoni effect is dependent on the liquid that is foaming usually not being pure. Generally, there are surfactants in the solution which will decrease the surface tension in the liquid. The surfactants will also clump together on the surface and form a layer as shown in the picture below.

For the Marangoni effect to occur, first the foam must be indented as shown in the first picture. This indentation will increase the local surface area. The surfactants have a larger diffusion time than the bulk of the solution; therefore, there is a smaller concentration of the surfactants in the indentation.

In addition, due to the stretching of the surface, the surface tension of the indented spot is greater than the surrounding area. Consequentially, since diffusion time for the surfactants is large, the Marangoni effect has time to take place. The difference in surface tension creates a gradient, which instigates fluid flow from areas of lower surface tension to areas of higher surface tension. The second picture shows the film at equilibrium after the Marangoni effect has taken place.[5]


Rybczynski and Hadamar developed an equation to calculate the velocity of bubbles that rise in foam with the assumption that the bubbles are spherical with a radius {\displaystyle r}r.

{\displaystyle u={\frac {2gr^{2}}{9\eta _{2}}}(\rho _{2}-\rho _{1})\left({\frac {3\eta _{1}+3\eta _{2}}{3\eta _{1}+2\eta _{2}}}\right)\!} u=\frac{2gr^2}{9\eta_2}(\rho_2-\rho_1)\left (\frac{3\eta_1+3\eta_2}{3\eta_1+2\eta_2}\right)\!

with velocity in units of centimeters per second. ρ1 and ρ2 is the density for a gas and liquid respectively in units of g/cm3 and ῃ1 and ῃ2 is the viscosity of the gas and liquid g/cm·s and g is the acceleration in units of cm/s2.

However, since the density and viscosity of a liquid is much greater than the gas, the density and viscosity of the gas can be neglected which yields the new equation for velocity of bubbles rising as:

{\displaystyle u={\frac {gr^{2}}{3\eta _{2}}}(\rho _{2})\!} u=\frac{gr^2}{3\eta_2}(\rho_2)\!

However, through experiments it has been shown that a more accurate model for bubbles rising is:

{\displaystyle u={\frac {2gr^{2}}{9\eta _{2}}}(\rho _{2}-\rho _{1})\!} u=\frac{2gr^2}{9\eta_2}(\rho_2-\rho_1)\!

Reasons for the deviations are due to the Marangoni effect and capillary pressure which affects the assumption that the bubbles are spherical. For laplace pressure of a curved gas liquid interface, the two principle radii of curvature at a point are R1 and R2.[6] With a curved interface, the pressure in one phase will be greater than the pressure in another phase; the capillary pressure Pc is given by the equation of:

{\displaystyle P_{c}=\gamma \left({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}\right)\!} P_c=\gamma\left (\frac{1}{R_1}+\frac{1}{R_2}\right)\!,

where {\displaystyle \gamma }\gamma is the surface tension. The bubble shown below is a gas (phase 1) in a liquid (phase 2) and point A designates the top of the bubble while point B designates the bottom of the bubble.

Bubble for hydrostatic pressure

At the top of the bubble at point A, the pressure in the liquid is assumed to be p0 as well as in the gas. At the bottom of the bubble at point B, the hydrostatic pressure is:

{\displaystyle P_{B},1=p_{0}+g\rho _{1}z\!} P_B,1=p_0+g\rho_1z\!
{\displaystyle P_{B},2=p_{0}+g\rho _{2}z\!} P_B,2=p_0+g\rho_2z\!

where ρ1 and ρ2 is the density for a gas and liquid respectively. The difference in hydrostatic pressure at the top of the bubble is 0, while the difference in hydrostatic pressure at the bottom of the bubble across the interface is gz(ρ2 − ρ1). Assuming that the radii of curvature at point A are equal and denoted by RA and that the radii of curvature at point B are equal and denoted by RB, then the difference in capillary pressure between point A and point B is:

{\displaystyle P_{c}=2\gamma \left({\frac {1}{R_{A}}}-{\frac {1}{R_{B}}}\right)\!} P_c=2\gamma\left (\frac{1}{R_A}-\frac{1}{R_B}\right)\!

At equilibrium, the difference in capillary pressure must be balanced by the difference in hydrostatic pressure. Hence,

{\displaystyle gz(\rho _{2}-\rho _{1})=2\gamma \left({\frac {1}{R_{A}}}-{\frac {1}{R_{B}}}\right)\!} gz(\rho_2-\rho_1)=2\gamma\left (\frac{1}{R_A}-\frac{1}{R_B}\right)\!

Since, the density of the gas is less than the density of the liquid the left hand side of the equation will always be positive. Therefore, the inverse of RA must be larger than the RB. Meaning that from the top of the bubble to the bottom of the bubble the radius of curvature will increase; therefore, without neglecting gravity the bubbles cannot be spherical. In addition, as z increases, this will cause the difference in RA and RB too, which means the bubble will deviate more from its shape the larger it grows.[4]

Foam destabilization occurs for several reasons. First, gravitation causes drainage of liquid to the foam base, which Rybczynski and Hadamar include in their theory; however, foam also destabilizes due to osmotic pressure causes drainage from the lamellas to the Plateau borders due to internal concentration differences in the foam, and Laplace pressure causes diffusion of gas from small to large bubbles due to pressure difference. In addition, films can break under disjoining pressure, These effects can lead to rearrangement of the foam structure at scales larger than the bubbles, which may be individual (T1 process) or collective (even of the “avalanche” type).

Experiments and characterizations[edit]

Being a multiscale system involving many phenomena, and a versatile medium, foam can be studied using many different techniques. Considering the different scales, experimental techniques are diffraction ones, mainly light scattering techniques (DWS, see below, static and dynamic light scattering, X rays and neutron scattering) at sub-micrometer scales, or microscopic ones. Considering the system as continuous, its bulk properties can be characterized by light transmittance but also conductimetry. The correlation between structure and bulk is evidenced more accurately by acoustics in particular. The organisation between bubbles has been studied numerically using sequential attempts of evolution of the minimum surface energy either at random (Pott’s model) or deterministic way (surface evolver). The evolution with time, i.e. the dynamics, can be simulated using these models, but also the bubble model (Durian) which considers the motion of individual bubbles.

Among possible examples, low scale observations of the structure done using reflectivity by the films between bubbles, of radiation, ponctual using laser or X rays beams, or more global using neutron scattering.

Reflection of radiation by a foam

Measurement principle of multiple light scattering coupled with vertical scanning

A typical light scattering (or diffusion) optical technique, multiple light scattering coupled with vertical scanning, is the most widely used technique to monitor the dispersion state of a product, hence identifying and quantifying destabilization phenomena.[7][8][9][10] It works on any concentrated dispersions without dilution, including foams. When light is sent through the sample, it is backscattered by the bubbles. The backscattering intensity is directly proportional to the size and volume fraction of the dispersed phase. Therefore, local changes in concentration (drainage, syneresis) and global changes in size (ripening, coalescence) are detected and monitored.


Liquid foams[edit]

Liquid foams can be used in fire retardant foam, such as those that are used in extinguishing fires, especially oil fires.

In some ways, leavened bread is a foam, as the yeast causes the bread to rise by producing tiny bubbles of gas in the dough. The dough has traditionally been understood as a closed-cell foam, in which the pores do not connect with each other. Cutting the dough releases the gas in the bubbles that are cut, but the gas in the rest of the dough cannot escape. When dough is allowed to rise too far, it becomes an open-cell foam, in which the gas pockets are connected. Now, if the dough is cut or the surface otherwise broken, a large volume of gas can escape, and the dough collapses. The open structure of an over-risen dough is easy to observe: instead of consisting of discrete gas bubbles, the dough consists of a gas space filled with threads of the flour-water paste. Recent research has indicated that the pore structure in bread is 99% interconnected into one large vacuole, thus the closed-cell foam of the moist dough is transformed into an open cell solid foam in the bread.[11]

The unique property of gas-liquid foams having very high specific surface area is exploited in the chemical processes of froth flotation and foam fractionation.

Solid foams[edit]

Solid foams are an important class of lightweight cellular engineering materials. These foams can be classified into two types based on their pore structure: open-cell-structured foams (also known as reticulated foams) and closed-cell foams.

Open-cell-structured foams contain pores that are connected to each other and form an interconnected network that is relatively soft. Open-cell foams will fill with whatever they are surrounded with. If filled with air, a relatively good insulator is the result, but, if the open cells fill with water, insulation properties would be reduced. Recent studies have put the focus on studying the properties of open-cell foams as an insulator material. Wheat gluten/TEOS bio-foams have been produced, showing similar insulator properties as for those foams obtained from oil-based resources.[12][13] Foam rubber is a type of open-cell foam.

Closed-cell foams do not have interconnected pores. The closed-cell foams normally have higher compressive strength due to their structures. However, closed-cell foams are also in general denser, require more material, and as a consequence are more expensive to produce. The closed cells can be filled with a specialized gas to provide improved insulation. The closed-cell structure foams have higher dimensional stability, low moisture absorption coefficients, and higher strength compared to open-cell-structured foams. All types of foam are widely used as core material in sandwich-structured composite materials.

From the early 20th century, various types of specially manufactured solid foams came into use. The low density of these foams makes them excellent as thermal insulators and flotation devices, and their lightness and compressibility makes them ideal as packing materials and stuffings.

Syntactic foam[edit]

Main article: Syntactic foam

A special class of closed-cell foams, known as syntactic foam, contains hollow particles embedded in a matrix material. The spheres can be made from several materials, including glass, ceramic, and polymers. The advantage of syntactic foams is that they have a very high strength-to-weight ratio, making them ideal materials for many applications, including deep-sea and space applications. One particular syntactic foam employs shape memory polymer as its matrix, enabling the foam to take on the characteristics of shape memory resins and composite materials; i.e., it has the ability to be reshaped repeatedly when heated above a certain temperature and cooled. Shape memory foams have many possible applications, such as dynamic structural support, flexible foam core, and expandable foam fill.

Integral skin foam[edit]

Integral skin foam, also known as self-skin foam, is a type of foam with a high-density skin and a low-density core. It can be formed in an open-mold process or a closed-mold process. In the open-mold process, two reactive components are mixed and poured into an open mold. The mold is then closed and the mixture is allowed to expand and cure. Examples of items produced using this process include arm rests, baby seats, shoe soles, and mattresses. The closed-mold process, more commonly known as reaction injection molding (RIM), injects the mixed components into a closed mold under high pressures.[14]


Main article: Defoamer

Foam, in this case meaning “bubbly liquid”, is also produced as an often-unwanted by-product in the manufacture of various substances. For example, foam is a serious problem in the chemical industry, especially for biochemical processes. Many biological substances, for example proteins, easily create foam on agitation or aeration. Foam is a problem because it alters the liquid flow and blocks oxygen transfer from air (thereby preventing microbial respiration in aerobic fermentation processes). For this reason, anti-foaming agents, like silicone oils, are added to prevent these problems. Chemical methods of foam control are not always desired with respect to the problems (i.e., contamination, reduction of mass transfer) they may cause especially in food and pharmaceutical industries, where the product quality is of great importance. In order to prevent foam formation, in such cases mechanical methods are mostly dominant over chemical ones.

Speed of sound[edit]

The acoustical property of the speed of sound through a foam is of interest when analyzing failures of hydraulic components. The analysis involves calculating total hydraulic cycles to fatigue failure. The speed of sound in a foam is determined by the mechanical properties of the gas creating the foam: oxygen, nitrogen, or combinations.

An assumption that the speed of sound based on the fluid properties of the liquid will lead to errors in calculating fatigue cycles to failure of mechanical hydraulic components. Using acoustical transducers and related instrumentation that set low limits (0–50,000 Hz with roll-off) will result in errors. The low roll-off during measurement of actual frequency of acoustic cycles results in miscalculation due to actual hydraulic cycles in the possible ranges of 1–1000 MHz or higher. Instrumentation systems are most revealing when cycle bandwidths exceed the actual measured cycles by a factor of 10 to 100. Associated instrumentation costs also increase by factors of 10 to 100.

Most moving hydro-mechanical components cycle at 0–50 Hz, but entrained gas bubbles resulting in a foamy condition of the associated hydraulic fluid results in actual hydraulic cycles that can exceed 1000 MHz even if the moving mechanical components do not cycle at the higher cycle frequency.



Shampoo (/ʃæmˈp/) is a hair care product, typically in the form of a viscous liquid, that is used for cleaning hair. Less commonly, shampoo is available in bar form, like a bar of soap. Shampoo is used by applying it to wet hair, massaging the product into the hair, and then rinsing it out. Some users may follow a shampooing with the use of hair conditioner.

The goal of using shampoo is to remove the unwanted build-up in the hair without stripping out so much sebum as to make hair unmanageable. Shampoo is generally made by combining a surfactant, most often sodium lauryl sulfate or sodium laureth sulfate, with a co-surfactant, most often cocamidopropyl betaine in water.

Specialty shampoos are available for people with dandruff, color-treated hair, gluten or wheat allergies, an interest in using an “all-natural”, “organic“, “botanical” or “plant-derived” product, and infants and young children (“baby shampoo” is less irritating). There are also shampoos intended for animals that may contain insecticides or other medications to treat skin conditions or parasite infestations such as fleas.

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The word shampoo entered the English language from India during the colonial era.[1] It dates to 1762, and is derived from Hindi chāmpo (चाँपो [tʃãːpoː]),[2][3] itself derived from the Sanskrit root capayati (चपयति, which means to press, knead, soothe).[4][5] Sake Dean Mahomed is identified as an early promoter of the practice in Britain.


In India, a variety of herbs and their extracts were used as shampoos since ancient times. A very effective early shampoo was made by boiling Sapindus with dried Indian gooseberry (aamla) and a few other herbs, using the strained extract. Sapindus, also known as soapberries or soapnuts, is called Ksuna (Sanskrit: क्षुण)[6] in ancient Indian texts and its fruit pulp contain saponins which are a natural surfactant. The extract of soapberries, a tropical tree widespread in India, creates a lather which Indian texts called phenaka (Sanskrit: फेनक).[7] It leaves the hair soft, shiny and manageable. Other products used for hair cleansing were shikakai (Acacia concinna), soapnuts (Sapindus), hibiscus flowers,[8][9] ritha (Sapindus mukorossi) and arappu (Albizzia amara).[10] Guru Nanak, the founding prophet and the first Guru of Sikhism, made references to soapberry tree and soap in 16th century.[11]

Cleansing with hair and body massage (champu) during daily strip wash was an indulgence of early colonial traders in India. When they returned to Europe, they introduced the newly learnt habits, including hair treatment they called shampoo.[12]


Swedish ad for toiletries, 1905/1906.

During the early stages of shampoo in Europe, English hair stylists boiled shaved soap in water and added herbs to give the hair shine and fragrance. Commercially made shampoo was available from the turn of the 20th century. A 1914 ad for Canthrox Shampoo in American Magazine showed young women at camp washing their hair with Canthrox in a lake; magazine ads in 1914 by Rexall featured Harmony Hair Beautifier and Shampoo.[13]

In 1927, liquid shampoo was invented by German inventor Hans Schwarzkopf in Berlin, whose name created a shampoo brand sold in Europe.

Originally, soap and shampoo were very similar products; both containing the same naturally derived surfactants, a type of detergent. Modern shampoo as it is known today was first introduced in the 1930s with Drene, the first shampoo using synthetic surfactants instead of soap.[14]


Early shampoos used in Indonesia were made from the husk and straw (merang) of rice. The husks and straws were burned into ash, and the ashes (which have alkaline properties) are mixed with water to form lather. The ashes and lather were scrubbed into the hair and rinsed out, leaving the hair clean, but very dry. Afterwards, coconut oil was applied to the hair in order to moisturize it.[15]

Pre-Columbian North America[edit]

Certain Native American tribes used extracts from North American plants as hair shampoo; for example the Costanoans of present-day coastal California used extracts from the coastal woodfern, Dryopteris expansa,[16]

Pre-Columbian South America[edit]

Before quinoa can be eaten the saponin must be washed out from the grain prior to cooking. Pre-Columbian Andean civilizations used this soapy by-product as a shampoo.[17]


Typical liquid shampoo

Shampoo is generally made by combining a surfactant, most often sodium lauryl sulfate or sodium laureth sulfate, with a co-surfactant, most often cocamidopropyl betaine in water to form a thick, viscous liquid. Other essential ingredients include salt (sodium chloride), which is used to adjust the viscosity, a preservative and fragrance.[18][19] Other ingredients are generally included in shampoo formulations to maximize the following qualities:

Many shampoos are pearlescent. This effect is achieved by addition of tiny flakes of suitable materials, e.g. glycol distearate, chemically derived from stearic acid, which may have either animal or vegetable origins. Glycol distearate is a wax. Many shampoos also include silicone to provide conditioning benefits.

Commonly used ingredients[edit]

  • Ammonium Chloride
  • Ammonium lauryl sulfate
  • Glycol
  • Sodium laureth sulfate is derived from coconut oils and is used to soften water and create a lather. There was some concern over this particular ingredient circa 1998 as evidence suggested it might be a carcinogen, and this has yet to be disproved, as many sources still describe it as irritating to the hair and scalp.[21]
  • Sodium lauryl sulfate
  • Sodium lauroamphoacetate is naturally derived from coconut oils and is used as a cleanser and counter-irritant. This is the ingredient that makes the product tear-free.
  • Polysorbate 20 (abbreviated as PEG(20)) is a mild glycol-based surfactant that is used to solubilize fragrance oils and essential oils; meaning it causes liquid to spread across and penetrate the surface of a solid (i.e. your hair).
  • Polysorbate 80 (abbreviated as PEG(80)) is a glycol used to emulsify (or disperse) oils in water (so the oils do not float on top like Italian salad dressing).
  • PEG-150 distearate is a simple thickener.
  • Citric acid is produced biochemically and is used as an antioxidant to preserve the oils in the product. While it is a severe eye-irritant, the sodium lauroamphoacetate counteracts that property. Citric acid is used to adjust the pH down to approximately 5.5. It is a fairly weak acid which makes the adjustment easier. Shampoos usually are at pH 5.5 because at slightly acidic pH, the scales on a hair follicle lie flat, making the hair feel smooth and look shiny. It also has a small amount of preservative action. Citric acid as opposed to any other acid will prevent bacterial growth.[citation needed]
  • Quaternium-15 is used as a bacterial and fungicidal preservative.
  • Polyquaternium-10 has nothing to do with the chemical quaternium-15; it acts as the conditioning ingredient, providing moisture and fullness to the hair.
  • Di-PPG-2 myreth-10 adipate is a water-dispersible emollient that forms clear solutions with surfactant systems
  • Methylisothiazolinone, or MIT, is a powerful biocide and preservative.

Ingredient and functional claims[edit]

In the USA, the Food and Drug Administration (FDA) mandates that shampoo containers accurately list ingredients on the products container. The government further regulates what shampoo manufacturers can and cannot claim as any associated benefit. Shampoo producers often use these regulations to challenge marketing claims made by competitors, helping to enforce these regulations. While the claims may be substantiated however, the testing methods and details of such claims are not as straightforward. For example, many products are purported to protect hair from damage due to ultraviolet radiation. While the ingredient responsible for this protection does block UV, it is not often present in a high enough concentration to be effective. The North American Hair Research Society has a program to certify functional claims based on third party testing. Shampoos made for treating medical conditions such as dandruff,[22] itchy scalp are regulated as OTC drugs[23] in the US marketplace. In other parts of the world such as the EU, there is a requirement for the anti-dandruff claim to be substantiated, but it is not considered to be a medical problem.

Health risks[edit]

A number of contact allergens are used as ingredients in shampoos, and contact allergy caused by shampoos is well known.[24] Patch testing can identify ingredients to which patients are allergic, after which a physician can help the patient find a shampoo that is free of the ingredient to which they are allergic.[24][25]

Specialized shampoos[edit]


Cosmetic companies have developed shampoos specifically for those who have dandruff. These contain fungicides such as ketoconazole, zinc pyrithione and selenium sulfide, which reduce loose dander by killing Malassezia furfur. Coal tar and salicylate derivatives are often used as well.

Despite a big success of medicated shampoos there are also other alternatives for people who dislike using a lot of chemicals. Organic, natural shampoos can be a suitable alternative. These shampoos often use tea tree oil, essential oils and extracts.[26][verification needed]

Colored hair[edit]

Many companies have also developed color-protection shampoos suitable for colored hair; many of these shampoos contain gentle cleansers, or so the companies claim.

Gluten-free or wheat-free[edit]

Many people suffer from eczema on their palms and their head.[27] Some find that wheat or gluten (the protein found in many grains including wheat) is the cause, particularly if they are sensitive to this in food; e.g. celiac disease wheat allergy. Shampoo can often go into the mouth, particularly for children, so all individuals who are on gluten-free diets may prefer to find a gluten-free shampoo. Shampoo manufacturers are starting to recognize this and there are now gluten-free and wheat-free products available.

Wheat derivatives and ingredients from the other gluten grains are commonly used as binders to help the shampoo stick together and are also used as emollients in the form of oils. Following is a list of grain-derived shampoo ingredients.[28] Most of these ingredients do not theoretically contain any intact wheat proteins, but may do so due to incomplete processing or contamination.

  • Triticum vulgare (wheat), hordeum vulgare (barley), secale cereale (rye), or avena sativa (oats), including any oil, protein, hydrosylate, or other extract from any part of the plant.
  • Tocopherol/Tocopheryl acetate (Vitamin E), which may be derived from wheat
  • Hydrolyzed wheat protein or hydrolyzed wheat starch, also sometimes listed as hydrolyzed vegetable protein, stearyldimoniumhydroxypropyl or hydroxypropyltrimonium
  • Cyclodextrin, which may be produced from starch by means of enzymatic conversion
  • Amino peptide complex
  • Maltodextrin, dextrin, dextrin palmitate, or (hydrolyzed) malt extract
  • Phytosphingosine extract
  • Amino peptide complex
  • prolamine
  • Beta glucan
  • Disodium wheat Germamido PEG-2-Sulfosuccinat
  • Fermented grain extract
  • AMP-Isostearoyl
  • PG-Propyl Silanetriol
  • PVP crosspolymer
  • Ethyldimonium ethosulfate
  • Yeast extract
  • Phytospingosine extract
  • “Fragrance” is a broad category that may contain many chemicals that are otherwise unlisted on the label.[29]


Some companies use “all-natural”, “organic“, “botanical“, or “plant-derived” ingredients (such as plant extracts or oils), combining these additions with one or more typical surfactants. The use of the term “natural” is not regulated in any form, leading many companies to “green-wash” consumers into buying shampoos with harsh, stripping surfactants without their knowledge. A company may also slightly change the name of a surfactant to another acceptable form in order to fool unwitting customers.[30]


Shampoo for infants and young children is formulated so that it is less irritating and usually less prone to produce a stinging or burning sensation if it were to get into the eyes. For example, Johnson’s Baby Shampoo advertises under the premise of “No More Tears”. This is accomplished by one or more of the following formulation strategies.

  1. dilution, in case the product comes in contact with eyes after running off the top of the head with minimal further dilution
  2. adjusting pH to that of non-stress tears, approximately 7, which may be a higher pH than that of shampoos which are pH adjusted for skin or hair effects, and lower than that of shampoo made of soap
  3. use of surfactants which, alone or in combination, are less irritating than those used in other shampoos
  4. use of nonionic surfactants of the form of polyethoxylated synthetic glycolipids and polyethoxylated synthetic monoglycerides, which counteract the eye sting of other surfactants without producing the anesthetizing effect of alkyl polyethoxylates or alkylphenol polyethoxylates

The distinction in 4 above does not completely surmount the controversy over the use of shampoo ingredients to mitigate eye sting produced by other ingredients, or the use of the products so formulated. The considerations in 3 and 4 frequently result in a much greater multiplicity of surfactants being used in individual baby shampoos than in other shampoos, and the detergency or foaming of such products may be compromised thereby. The monoanionic sulfonated surfactants and viscosity-increasing or foam stabilizing alkanolamides seen so frequently in other shampoos are much less common in the better baby shampoos.


Shampoo intended for animals may contain insecticides or other medications for treatment of skin conditions or parasite infestations such as fleas or mange. These must never be used on humans. While some human shampoos may be harmful when used on animals, any human haircare products that contain active ingredients or drugs (such as zinc in anti-dandruff shampoos) are potentially toxic when ingested by animals. Special care must be taken not to use those products on pets. Cats are at particular risk due to their instinctive method of grooming their fur with their tongues. Shampoos that are especially designed to be used on pets, commonly dogs and cats, are normally intended to do more than just clean the pet’s coat or skin. Most of these shampoos contain ingredients which act differently and are meant to treat a skin condition or an allergy or to fight against fleas. The main ingredients contained by pet shampoos can be grouped in insecticidals, antiseborrheic, antibacterials, antifungals, emollients, emulsifiers and humectants. Whereas some of these ingredients may be efficient in treating some conditions, pet owners are recommended to use them according to their veterinarian‘s indications because many of them cannot be used on cats or can harm the pet if it is misused. Generally, insecticidal pet shampoos contain pyrethrin, pyrethroids (such as permethrin and which may not be used on cats) and carbaryl. These ingredients are mostly found in shampoos that are meant to fight against parasite infestations. Antifungal shampoos are used on pets with yeast or ringworm infections. These might contain ingredients such as miconazole, chlorhexidine, providone iodine, ketoconazole or selenium sulfide (which cannot be used on cats). Bacterial infections in pets are sometimes treated with antibacterial shampoos. They commonly contain benzoyl peroxide, chlorhexidine, povidone iodine, triclosan, ethyl lactate, or sulfur. Antipruritic shampoos are intended to provide relief of itching due to conditions such as atopy and other allergies.[31] These usually contain colloidal oatmeal, hydrocortisone, Aloe vera, pramoxine hydrochloride, menthol, diphenhydramine, sulfur or salicylic acid. These ingredients are aimed to reduce the inflammation, cure the condition and ease the symptoms at the same time while providing comfort to the pet. Antiseborrheic shampoos are those especially designed for pets with scales or those with excessive oily coats. These shampoos are made of sulfur, salicylic acid, refined tar (which cannot be used on cats), selenium sulfide (cannot be used on cats) and benzoyl peroxide. All these are meant to treat or prevent seborrhea oleosa, which is a condition characterized by excess oils. Dry scales can be prevented and treated with shampoos that contain sulfur or salicylic acid and which can be used on both cats and dogs. Emollient shampoos are efficient in adding oils to the skin and relieving the symptoms of a dry and itchy skin. They usually contain oils such as almond, corn, cottonseed, coconut, olive, peanut, Persia, safflower, sesame, lanolin, mineral or paraffin oil. The emollient shampoos are typically used with emulsifiers as they help distributing the emollients. These include ingredients such as cetyl alcohol, laureth-5, lecithin, PEG-4 dilaurate, stearic acid, stearyl alcohol, carboxylic acid, lactic acid, urea, sodium lactate, propylene glycol, glycerin, or polyvinylpyrrolidone. Although some of the pet shampoos are highly effective, some others may be less effective for some condition than another. Yet, although natural pet shampoos exist, it has been brought to attention that some of these might cause irritation to the skin of the pet. Natural ingredients that might be potential allergens for some pets include eucalyptus, lemon or orange extracts and tea tree oil.[32] On the contrary, oatmeal appears to be one of the most widely skin-tolerated ingredients that is found in pet shampoos. Most ingredients found in a shampoo meant to be used on animals are safe for the pet as there is a high likelihood that the pets will lick their coats, especially in the case of cats. Pet shampoos which include fragrances, deodorants or colors may harm the skin of the pet by causing inflammations or irritation. Shampoos that do not contain any unnatural additives are known as hypoallergenic shampoos and are increasing in popularity.


Solid shampoos or shampoo bars use as their surfactants soaps or other surfactants formulated as solids. They have the advantage of being spill-proof. They are easy to apply; one may simply rub the bar over wet hair, and work the soaped hair into a low lather.

Jelly and gel[edit]

Stiff, non-pourable clear gels to be squeezed from a tube were once popular forms of shampoo, and can be produced by increasing a shampoo’s viscosity. This type of shampoo cannot be spilled, but unlike a solid, it can still be lost down the drain by sliding off wet skin or hair.

Paste and cream[edit]

Shampoos in the form of pastes or creams were formerly marketed in jars or tubes. The contents were wet but not completely dissolved. They would apply faster than solids and dissolve quickly.


Antibacterial shampoos are often used in veterinary medicine for various conditions,[33][34] as well as in humans before some surgical procedures.[35][36]

No Poo Movement[edit]

Main article: No poo

Closely associated with environmentalism, the “no poo” movement consists of people rejecting the societal norm of frequent shampoo use. Some adherents of the no poo movement use baking soda or vinegar to wash their hair, while others use diluted honey. Other people use nothing, rinsing their hair only with conditioner.[37][38]


In the 1970s, ads featuring Farrah Fawcett and Christie Brinkley asserted that it was unhealthy not to shampoo several times a week. This mindset is reinforced by the greasy feeling of the scalp after a day or two of not shampooing. Using shampoo every day removes sebum, the oil produced by the scalp. This causes the sebaceous glands to produce oil at a higher rate, to compensate for what is lost during shampooing. According to Michelle Hanjani, a dermatologist at Columbia University, a gradual reduction in shampoo use will cause the sebum glands to produce at a slower rate, resulting in less grease in the scalp.[39] Although this approach might seem unappealing to some individuals, many people try alternate shampooing techniques like baking soda and vinegar in order to avoid chemicals and ingredients used in many shampoos that make hair greasy over time.[40]

from wikipedia


In chemistry, a soap is a salt of a fatty acid.[1] Household uses for soaps include washing, bathing, and other types of housekeeping, where soaps act as surfactants, emulsifying oils to enable them to be carried away by water. In industry they are also used in textile spinning[further explanation needed] and are important components of some lubricants.

Soaps for cleaning are obtained by treating vegetable or animal oils and fats with a strong base, such as sodium hydroxide or potassium hydroxide in an aqueous solution. Fats and oils are composed of triglycerides; three molecules of fatty acids attach to a single molecule of glycerol.[2] The alkaline solution, which is often called lye (although the term “lye soap” refers almost exclusively to soaps made with sodium hydroxide), brings about a chemical reaction known as saponification.

In this reaction, the triglyceride fats first hydrolyze into free fatty acids, and then these combine with the alkali to form crude soap: an amalgam of various soap salts, excess fat or alkali, water, and liberated glycerol (glycerin). The glycerin, a useful by-product, can remain in the soap product as a softening agent, or be isolated for other uses.[2]

Soaps are key components of most lubricating greases, which are usually emulsions of calcium soap or lithium soap and mineral oil.[3] Many other metallic soaps are also useful, including those of aluminium, sodium, and mixtures of them. Such soaps are also used as thickeners to increase the viscosity of oils. In ancient times, lubricating greases were made by the addition of lime to olive oil.[4]

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Mechanism of cleansing soaps[edit]

Structure of a micelle, a cell-like structure formed by the aggregation of soap subunits (such as sodium stearate): The exterior of the micelle is hydrophilic (attracted to water) and the interior is lipophilic (attracted to oils).

Action of soap[edit]

When used for cleaning, soap allows insoluble particles to become soluble in water, so they can then be rinsed away. For example: oil/fat is insoluble in water, but when a couple of drops of dish soap are added to the mixture, the oil/fat solubilizes into the water. The insoluble oil/fat molecules become associated inside micelles, tiny spheres formed from soap molecules with polar hydrophilic (water-attracting) groups on the outside and encasing a lipophilic (fat-attracting) pocket, which shields the oil/fat molecules from the water making it soluble. Anything that is soluble will be washed away with the water.

Effect of the alkali[edit]

The type of alkali metal used determines the kind of soap product. Sodium soaps, prepared from sodium hydroxide, are firm, whereas potassium soaps, derived from potassium hydroxide, are softer or often liquid. Historically, potassium hydroxide was extracted from the ashes of bracken or other plants. Lithium soaps also tend to be hard—these are used exclusively in greases.

Effects of fats[edit]

Soaps are derivatives of fatty acids. Traditionally they have been made from triglycerides (oils and fats).[5] Triglyceride is the chemical name for the triesters of fatty acids and glycerin. Tallow, i.e., rendered beef fat, is the most available triglyceride from animals. Its saponified product is called sodium tallowate. Typical vegetable oils used in soap making are palm oil, coconut oil, olive oil, and laurel oil. Each species offers quite different fatty acid content and hence, results in soaps of distinct feel. The seed oils give softer but milder soaps. Soap made from pure olive oil is sometimes called Castile soap or Marseille soap, and is reputed for being extra mild. The term “Castile” is also sometimes applied to soaps from a mixture of oils, but a high percentage of olive oil.

Fatty acid content of various fats used for soapmaking
Lauric acid Myristic acid Palmitic acid Stearic acid Oleic acid Linoleic acid Linolenic acid
fats C12 saturated C14 saturated C16 saturated C18 saturated C18 monounsaturated C18 diunsaturated C18 triunsaturated
Tallow 0 4 28 23 35 2 1
Coconut oil 48 18 9 3 7 2 0
Palm kernel oil 46 16 8 3 12 2 0
Laurel oil 54 0 0 0 15 17 0
Olive oil 0 0 11 2 78 10 0
Canola oil 0 1 3 2 58 9 23

History of soaps[edit]

Early history[edit]

Box for Amigo del Obrero (Worker’s Friend) soap from the 20th century, part of the Museo del Objeto del Objeto collection

The earliest recorded evidence of the production of soap-like materials dates back to around 2800 BC in ancient Babylon.[6] A formula for soap consisting of water, alkali, and cassia oil was written on a Babylonian clay tablet around 2200 BC.

The Ebers papyrus (Egypt, 1550 BC) indicates the ancient Egyptians bathed regularly and combined animal and vegetable oils with alkaline salts to create a soap-like substance. Egyptian documents mention a soap-like substance was used in the preparation of wool for weaving.[citation needed]

In the reign of Nabonidus (556–539 BC), a recipe for soap consisted of uhulu [ashes], cypress [oil] and sesame [seed oil] “for washing the stones for the servant girls”.[7]

Ancient Roman era[edit]

The word sapo, Latin for soap, first appears in Pliny the Elder‘s Historia Naturalis, which discusses the manufacture of soap from tallow and ashes, but the only use he mentions for it is as a pomade for hair; he mentions rather disapprovingly that the men of the Gauls and Germans were more likely to use it than their female counterparts.[8] Aretaeus of Cappadocia, writing in the first century AD, observes among “Celts, which are men called Gauls, those alkaline substances that are made into balls […] called soap“.[9] The Romans’ preferred method of cleaning the body was to massage oil into the skin and then scrape away both the oil and any dirt with a strigil. The Gauls used soap made from animal fat.

A popular belief claims soap takes its name from a supposed Mount Sapo, where animal sacrifices were supposed to have taken place; tallow from these sacrifices would then have mixed with ashes from fires associated with these sacrifices and with water to produce soap, but there is no evidence of a Mount Sapo in the Roman world and no evidence for the apocryphal story. The Latin word sapo simply means “soap”; it was likely borrowed from an early Germanic language and is cognate with Latin sebum, “tallow”, which appears in Pliny the Elder’s account.[10] Roman animal sacrifices usually burned only the bones and inedible entrails of the sacrificed animals; edible meat and fat from the sacrifices were taken by the humans rather than the gods.

Zosimos of Panopolis, circa 300 AD, describes soap and soapmaking.[11] Galen describes soap-making using lye and prescribes washing to carry away impurities from the body and clothes. The use of soap for personal cleanliness became increasingly common in the 2nd century A.D. According to Galen, the best soaps were Germanic, and soaps from Gaul were second best. This is a reference to true soap in antiquity.[11]

Ancient China[edit]

A detergent similar to soap was manufactured in ancient China from the seeds of Gleditsia sinensis.[12] Another traditional detergent is a mixture of pig pancreas and plant ash called “Zhu yi zi”. True soap, made of animal fat, did not appear in China until the modern era.[13] Soap-like detergents were not as popular as ointments and creams.[12]

Middle East[edit]

A 12th-century Islamic document describes the process of soap production.[14] It mentions the key ingredient, alkali, which later becomes crucial to modern chemistry, derived from al-qaly or “ashes”.

By the 13th century, the manufacture of soap in the Islamic world had become virtually industrialized, with sources in Nablus, Fes, Damascus, and Aleppo.[15][16]

Medieval Europe[edit]

Soapmakers in Naples were members of a guild in the late sixth century (then under the control of the Eastern Roman Empire),[17] and in the eighth century, soap-making was well known in Italy and Spain.[18] The Carolingian capitulary De Villis, dating to around 800, representing the royal will of Charlemagne, mentions soap as being one of the products the stewards of royal estates are to tally. The lands of Medieval Spain were a leading soapmaker by 800, and soapmaking began in the Kingdom of England about 1200.[19]Soapmaking is mentioned both as “women’s work” and as the produce of “good workmen” alongside other necessities, such as the produce of carpenters, blacksmiths, and bakers.[20]

15th–19th centuries[edit]

Advertisement for Pears’ Soap, 1889

A 1922 magazine advertisement for Palmolive Soap

Liquid soap

Manufacturing process of soaps/detergents

In France, by the second half of the 15th century, the semi-industrialized professional manufacture of soap was concentrated in a few centers of ProvenceToulon, Hyères, and Marseille — which supplied the rest of France.[21] In Marseilles, by 1525, production was concentrated in at least two factories, and soap production at Marseille tended to eclipse the other Provençal centers.[22] English manufacture tended to concentrate in London.[23]

Finer soaps were later produced in Europe from the 16th century, using vegetable oils (such as olive oil) as opposed to animal fats. Many of these soaps are still produced, both industrially and by small-scale artisans. Castile soap is a popular example of the vegetable-only soaps derived from the oldest “white soap” of Italy.

In modern times, the use of soap has become commonplace in industrialized nations due to a better understanding of the role of hygiene in reducing the population size of pathogenic microorganisms. Industrially manufactured bar soaps first became available in the late 18th century, as advertising campaigns in Europe and America promoted popular awareness of the relationship between cleanliness and health.[24]

Until the Industrial Revolution, soapmaking was conducted on a small scale and the product was rough. In 1780 James Keir established a chemical works at Tipton, for the manufacture of alkali from the sulfates of potash and soda, to which he afterwards added a soap manufactory. The method of extraction proceeded on a discovery of Keir’s. Andrew Pears started making a high-quality, transparent soap in 1807[25] in London. His son-in-law, Thomas J. Barratt, opened a factory in Isleworth in 1862.

William Gossage produced low-priced, good-quality soap from the 1850s. Robert Spear Hudson began manufacturing a soap powder in 1837, initially by grinding the soap with a mortar and pestle. American manufacturer Benjamin T. Babbitt introduced marketing innovations that included sale of bar soap and distribution of product samples. William Hesketh Lever and his brother, James, bought a small soap works in Warrington in 1886 and founded what is still one of the largest soap businesses, formerly called Lever Brothers and now called Unilever. These soap businesses were among the first to employ large-scale advertising campaigns.

Liquid soap[edit]

See also: Detergent

Liquid soap was not invented until the nineteenth century; in 1865, William Shepphard patented a liquid version of soap. In 1898, B.J. Johnson developed a soap (made of palm and olive oils); his company (the B.J. Johnson Soap Company) introduced “Palmolive” brand soap that same year. This new brand of the new kind of soap became popular rapidly, and to such a degree that B.J. Johnson Soap Company changed its name to Palmolive.[26]

In the early 1900s, other companies began to develop their own liquid soaps. Such products as Pine-Sol and Tide appeared on the market, making the process of cleaning things other than skin (e.g., clothing, floors, bathrooms) much easier.

Liquid soap also works better for more traditional/non-machine washing methods, such as using a washboard.[27]

Soap-making processes[edit]

The industrial production of soap involves continuous processes, such as continuous addition of fat and removal of product. Smaller-scale production involves the traditional batch processes. The three variations are: the ‘cold process’, wherein the reaction takes place substantially at room temperature, the ‘semiboiled’ or ‘hot process’, wherein the reaction takes place near the boiling point, and the ‘fully boiled process’, wherein the reactants are boiled at least once and the glycerol is recovered. There are several types of ‘semiboiled’ hot process methods, the most common being DBHP (Double Boiler Hot Process) and CPHP (Crock Pot Hot Process).[28] Most soapmakers, however, continue to prefer the cold process method. The cold process and hot process (semiboiled) are the simplest and typically used by small artisans and hobbyists producing handmade decorative soaps. The glycerine remains in the soap and the reaction continues for many days after the soap is poured into molds. The glycerine is left during the hot-process method, but at the high temperature employed, the reaction is practically completed in the kettle, before the soap is poured into molds. This simple and quick process is employed in small factories all over the world.

Handmade soap from the cold process also differs from industrially made soap in that an excess of fat is used, beyond that needed to consume the alkali (in a cold-pour process, this excess fat is called “superfatting”), and the glycerine left in acts as a moisturizing agent. However, the glycerine also makes the soap softer and less resistant to becoming “mushy” if left wet. Since it is better to add too much oil and have left-over fat, than to add too much lye and have left-over lye, soap produced from the hot process also contains left-over glycerine and its concomitant pros and cons. Further addition of glycerine and processing of this soap produces glycerin soap. Superfatted soap is more skin-friendly than one without extra fat. However, if too much fat is added, it can leave a “greasy” feel to the skin. Sometimes, an emollient additive, such as jojoba oil or shea butter, is added “at trace” (i.e., the point at which the saponification process is sufficiently advanced that the soap has begun to thicken in the cold process method) in the belief that nearly all the lye will be spent and it will escape saponification and remain intact. In the case of hot-process soap, an emollient may be added after the initial oils have saponified so they remain unreacted in the finished soap. Superfatting can also be accomplished through a process known as “lye discount” in which the soap maker uses less alkali than required instead of adding extra fats.

Cold process[edit]

The lye is dissolved in water.

Even in the cold soap making process, some heat is usually required; the temperature is usually raised to a point sufficient to ensure complete melting of the fat being used. The batch may also be kept warm for some time after mixing to ensure the alkali (hydroxide) is completely used up. This soap is safe to use after about 12–48 hours, but is not at its peak quality for use for several weeks.

Cold-process soapmaking requires exact measurements of lye and fat amounts and computing their ratio, using saponification charts to ensure the finished product does not contain any excess hydroxide or too much free unreacted fat. Saponification charts should also be used in hot processes, but are not necessary for the “fully boiled hot-process” soaping.

Historically, lye used in the cold process was made from scratch using rainwater and ashes. Soapmakers deemed the lye solution ready for use when an egg would float in it. Homemade lye making for this process was unpredictable and therefore eventually led to the discovery of sodium hydroxide by English chemist Sir Humphry Davy in the early 1800s.

A cold-process soapmaker first looks up the saponification value for each unique fat on an oil specification sheet. Oil specification sheets contain laboratory test results for each fat, including the precise saponification value of the fat. The saponification value for a specific fat will vary by season and by specimen species.[29] This value is used to calculate the exact amount of sodium hydroxide to react with the fat to form soap. The saponification value must be converted into an equivalent sodium hydroxide value for use in cold process soapmaking. Excess unreacted lye in the soap will result in a very high pH and can burn or irritate skin; not enough lye leaves the soap greasy. Most soap makers formulate their recipes with a 2–5% deficit of lye, to account for the unknown deviation of saponification value between their oil batch and laboratory averages.

The lye is dissolved in water. Then, the oils are heated, or melted if they are solid at room temperature. Once the oils are liquefied and the lye is fully dissolved in water, they are combined. This lye-fat mixture is mixed until the two phases (oils and water) are fully emulsified. Emulsification is most easily identified visually when the soap exhibits some level of “trace”, which is the thickening of the mixture. Many modern-day amateur soapmakers often use a stick blender to speed up this process. There are varying levels of trace. Depending on how additives will affect trace, they may be added at light trace, medium trace, or heavy trace. After much stirring, the mixture turns to the consistency of a thin pudding. “Trace” corresponds roughly to viscosity. Essential oils and fragrance oils can be added with the initial soaping oils, but solid additives such as botanicals, herbs, oatmeal, or other additives are most commonly added at light trace, just as the mixture starts to thicken.[citation needed]

The batch is then poured into molds, kept warm with towels or blankets, and left to continue saponification for 12 to 48 hours. (Milk soaps or other soaps with sugars added are the exception. They typically do not require insulation, as the presence of sugar increases the speed of the reaction and thus the production of heat.) During this time, it is normal for the soap to go through a “gel phase”, wherein the opaque soap will turn somewhat transparent for several hours, before once again turning opaque.

After the insulation period, the soap is firm enough to be removed from the mold and cut into bars. At this time, it is safe to use the soap, since saponification is in essence complete. However, cold-process soaps are typically cured and hardened on a drying rack for 2–6 weeks before use. During this cure period, trace amounts of residual lye are consumed by saponification and excess water evaporates.

During the curing process, some molecules in the outer layer of the solid soap react with the carbon dioxide of the air and produce a dusty sheet of sodium carbonate. This reaction is more intense if the mass is exposed to wind or low temperatures.

Hot processes[edit]

Hot-processed soaps are created by encouraging the saponification reaction by adding heat to speed up the reaction. In contrast with cold-pour soap which is poured into molds and for the most part only then saponifies, hot-process soaping for the most part saponifies the oils completely and only then is poured into molds.

In the hot process, the hydroxide and the fat are heated and mixed together at 80–100 °C, a little below boiling point, until saponification is complete, which, before modern scientific equipment, the soapmaker determined by taste (the sharp, distinctive taste of the hydroxide disappears after it is saponified) or by eye; the experienced eye can tell when gel stage and full saponification has occurred. Beginners can find this information through research and classes. Tasting soap for readiness is not recommended, as sodium and potassium hydroxides, when not saponified, are highly caustic.

An advantage of the fully boiled hot process in soapmaking is the exact amount of hydroxide required need not be known with great accuracy. They originated when the purity of the alkali hydroxides were unreliable, as these processes can use even naturally found alkalis, such as wood ashes and potash deposits. In the fully boiled process, the mix is actually boiled (100+ °C), and, after saponification has occurred, the “neat soap” is precipitated from the solution by adding common salt, and the excess liquid is drained off. This excess liquid carries away with it much of the impurities and color compounds in the fat, to leave a purer, whiter soap, and with practically all the glycerine removed. The hot, soft soap is then pumped into a mold. The spent hydroxide solution is processed for recovery of glycerine.


Logs of soap after demolding.

Many commercially available soap molds are made of silicone or various types of plastic, although many soapmaking hobbyists may use cardboard boxes lined with a plastic film. Wooden molds, unlined or lined with silicone sleeves, are also readily available to the general public. Soaps can be made in long bars that are cut into individual portions, or cast into individual molds.

Purification and finishing[edit]

In the fully boiled process on an industrial scale, the soap is further purified to remove any excess sodium hydroxide, glycerol, and other impurities, color compounds, etc. These components are removed by boiling the crude soap curds in water and then precipitating the soap with salt.

At this stage, the soap still contains too much water, which has to be removed. This was traditionally done on chill rolls, which produced the soap flakes commonly used in the 1940s and 1950s. This process was superseded by spray dryers and then by vacuum dryers.

The dry soap (about 6–12% moisture) is then compacted into small pellets or noodles. These pellets or noodles are then ready for soap finishing, the process of converting raw soap pellets into a saleable product, usually bars.

Soap pellets are combined with fragrances and other materials and blended to homogeneity in an amalgamator (mixer). The mass is then discharged from the mixer into a refiner, which, by means of an auger, forces the soap through a fine wire screen. From the refiner, the soap passes over a roller mill (French milling or hard milling) in a manner similar to calendering paper or plastic or to making chocolate liquor. The soap is then passed through one or more additional refiners to further plasticize the soap mass. Immediately before extrusion, the mass is passed through a vacuum chamber to remove any trapped air. It is then extruded into a long log or blank, cut to convenient lengths, passed through a metal detector, and then stamped into shape in refrigerated tools. The pressed bars are packaged in many ways.

Sand or pumice may be added to produce a scouring soap. The scouring agents serve to remove dead cells from the skin surface being cleaned. This process is called exfoliation. Many newer materials that are effective, yet do not have the sharp edges and poor particle size distribution of pumice, are used for exfoliating soaps.

To make antibacterial soap, compounds such as triclosan or triclocarban can be added. There is some concern that use of antibacterial soaps and other products might encourage antibiotic resistance in microorganisms.[30]

Dishwashing liquid

Dishwashing liquid (BrE: washing-up liquid), known as dishwashing soap, dish detergent and dish soap, is a detergent used to assist in dishwashing. It is usually a highly-foaming mixture of surfactants with low skin irritation, and is primarily used for hand washing of glasses, plates, cutlery, and cooking utensils in a sink or bowl. In addition to its primary use, dishwashing liquid also has various informal applications, such as for creating bubbles, clothes washing and cleaning oil-affected birds.

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Main article: Detergent


carbonate) is used for dishwashing,[1] and may be used in areas with hard water.[2] It was used for dishwashing before detergents were invented in Germany during World War I.[3] Liquid detergent used for dishwashing was first manufactured in the middle of the 20th century. Dishwashing detergent producers started production in the United States in the 1930–1940s.[3][4] Teepol, the first such in Europe, commenced production in 1942.[5]

In 2005, dishwashing detergent retail sales totaled nearly USD $10 billion worldwide.[4]


Dishwashing detergents for dishwashers are manufactured and marketed variously as cartridges, gel, liquids, pacs, powder, and tablets.[6] Any dishwashing liquid may contain bleach, enzymes, or rinsing aids.[6] Some dishwashing detergents may be homemade, using ingredients such as borax, essential oil, eucalyptus oil and grated bar soap, among others.[7]

Common ingredients[edit]

The main ingredient is water; the main active ingredients are detergents. There are other thickening and stabilizing agents.[8] Other ingredients may include surfactants, hydrotrope, salts, preservatives, fragrances, and dyes.[4]

Surfactants remove grease and stuck food particles.[4] They may also provide foam.[4]

Some dishwashing detergents may contain phosphorus, an ingredient which at least two states within the United States have limited use in dishwashing detergent.[9][10] According to the Washington Post, phosphorus keeps “minerals from interfering with the cleaning process and prevent food particles from depositing again on dishes.”[10] According to Time magazine, “One reason detergent makers have been using large amounts of phosphorus is that it binds with dirt and keeps it suspended in water, allowing the other cleaning agents to do their best work. Phosphorus is especially important in regions with hard water because the presence of lots of minerals can interfere with cleaning agents.”[11] Phosphorus that runs into freshwater lakes and rivers can cause algal blooms.[10][11]Phosphate-free detergent reduces the amount of phosphate wastewater treatment plants must clean up.[10] In the 21st century phosphates began to be reduced in percentage terms as an ingredient, leading to a New York Times report that said “low- or phosphate-free dishwasher detergents it tested, including those from environmentally friendly product lines that have been on the market for years, none matched the performance of products with phosphates”.[12]

In 2010, the United States FDA raised health concerns over triclosan, an antibacterial substance used in some dish liquids.[13] Elsewhere, triclosan has been found to create problems at wastewater treatment plants, whereby it can “sabotage some sludge-processing microbes and promote drug resistance in others.”[14] The United States FDA has found that triclosan provides no health benefits over soap and water.[15] As of 2014, at least one state within the United States has banned triclosan in dishwashing liquids.[15]

Many dishwashing liquids contain perfume which can cause irritant or allergic contact dermatitis.[16]


Euromonitor International research on dishwashing trends in eighty countries identified producers and brands with the largest 2013 retail value shares.[17] Five multinational companies (Procter and Gamble, Colgate-Palmolive, Henkel, Reckitt Benckiser, Unilever and HITRO PLUS),collectively held the greatest retail value shares in sixty-five of those countries.[17] Summaries below show percentages of retail value shares and leading brand names in each country, according to Euromonitor International’s 2013 reports.

Procter and Gamble held the highest retail value share percentages in twenty countries:[17] with Fairy brand, United Kingdom, Estonia, Saudi Arabia (56%), United Arab Emirates (34%), Latvia (35%), Lithuania (32%), Finland (23%), Serbia (38%), Bosnia-Herzegovina (30%), Georgia (26%) and Uzbekistan (26%); Sweden (39%) with brand Yes, the Swedish Fairy brand; Greece (40%) with Fairy and Ava brands; with Fairy and Mif brands, Kazakhstan (28%) and Russia (29%); and Ukraine (41%) with Fairy and Gala brands; Canada (39%) with Cascade and Dawn brands; United States (52%) with Cascade brand; Mexico (44%) with Salvo and Dawn brands; Philippines (54%) with Joy brand.

Unilever held highest retail value share percentages in thirteen countries:[17] Netherlands (25%); with Sunlight brand, Cameroon (32%), South Africa (56%), Indonesia, Thailand (66%); India (61%) with Vim brand; Vietnam (56%) with Sunlight Green Tea, Sunlight Lemon, and Sunlight Active Gel; France (34%) with Sun Turbo Gel and Sun tout en 1; with Sun brand, Switzerland (31%), and Belgium (30%); Argentina (54%) with Ala and Ala Ultra brands; Chile (57%) with Quix brand; and Uruguay (56%) with Hurra Nevex and Cif brands.

Henkel held highest retail value share percentages in nine countries:[17] Germany (29%); Romania (35%); Algeria (22%) with Isis Pril; Egypt with KGaA, Port Said Detergents, and Pril brands; Croatia (22%) with Pur and Somat brands; Slovakia (33%) with Somat brand; Slovenia (35%) with Pril brand; Hungary (30%) with Pur and Somat brands; and Azerbaijan (22%) with Pril and Pemolux brands.

Reckitt Benckiser held highest retail value share percentages in nine countries:[17] Italy (31%), Spain (29%); with Finish brand: Australia (38%), New Zealand (38%), Austria (32%), Ireland (29%), and Israel (27%); Denmark (30%) with Neophos brand; and Portugal (22%) with Calgonit brand.

Colgate-Palmolive held highest retail value share percentages in nine countries:[17] Morocco (23%); Tunisia (24%) with Citrol brand; Malaysia (29%); Pakistan (55%) with Max brand; with Axion, Costa Rica (39%), Dominican Republic (31%), Colombia (40%), and Ecuador (39%); Guatemala (39%) with Axion and Doña Blanca brands.

Research summaries for three countries listed combined retail value shares that included domestic and international producers:[17] Brazil‘s domestic producers led hand dishwashing products with Química Amparo, Bombril, and Flora Produtos de Higiene e Limpeza; Poland’s Grupa Inco with Ludwik and Lucek brands, and Henka Polska with Pur and Somat brands, led sales with a combined retail value share of 46%; and in Belarus the Russian company PZ Cussons PLC accounted for 24% of retail value shares, with Morning Fresh brand, followed by Procter and Gamble (20%) and Henkel (19%).

Summaries for two countries listed combined results for international companies and brands:[17] in the Czech Republic, Procter and Gamble, Henkel, and Reckitt Benckiser held a combined 71% retail value share; and in Turkey Reckitt Benckiser’s Finish brand led with 32% retail value share for automatic dishwashing, while Henkel had 31% retail value share, and Pril brand led hand dishwashing liquid with a 42% retail value share.

In fifteen markets, domestic producers held the greatest 2013 retail value share with local brands:[17] in China, Guangzhou Liby Enterprise Group held a 30% retail value share; Hong Kong company Lam Soon held 44% retail value share with Axe and Labour brands; Singapore company Lion Corp led sales with Mama Lemon, Mama Lemon Antibacterial, and Mama Royal brands; South Korean company LG Household & Health Care Ltd. held a 54% retail value share with dishwashing brands Pong Pong, Natural Pong and Safe; in Japan, Kao held a 33% retail value share with CuCute brand; Alimentos Polar in Venezuela held a 37% retail value share with Las Laves brand. In Nigeria, PZ Industries PLC held a 63% share, with Morning Fresh brand. In Norway, Lilleborg AS held 71% retail value share, with Sun and Zalo brands; in Bulgaria, Ficosota Syntez held 29% retail value share, with Eho and Feya brands; in Macedonia, Saponia dd held 22% retail value share; in Iran, Paxan Co. held 24% retail value share with Barf, Orchid, Goli, and Pride brands; in Bolivia, Astrix SA held 47%retail value share with Ola brand; in Peru, Intradevco Industrial SA held 63% retail value share with Sapolio brand; in Venezuela, Alimentos Polar held 37% retail value share with Las Llaves brand. The summary of dishwashing in Kenya noted most consumers there use alternatives like laundry detergent powder or soap instead of dishwashing liquids, but listed Haco as the leading dishwashing liquid, from Haco Tiger Brands Ltd.[18]

Primary uses[edit]

Dishwashing liquid is used primarily for removing food from used dishes and tableware.[4][6] Heavy soil (large food particles) is generally scraped from the dishes before using.[6] Detergent formula can vary based on use (hand or automatic).[4]

Hand dishwashing[edit]

Dishwashing liquid mixed with water on the left side of a sink

Hand dishwashing is generally performed in the absence of a dishwashing machine, when large “hard-to-clean” items are present, or through preference.[4] Some dishwashing liquids can harm household silver, fine glassware, anything with gold leaf, disposable plastics, and any objects made of brass, bronze, cast iron, pewter, tin, or wood, especially when combined with hot water and the action of a dishwasher.[6] When dishwashing liquid is used on such objects it is intended that they be washed by hand.[6]

Hand dishwashing detergents utilize surfactants to play the primary role in cleaning.[4] The reduced surface tension of dishwashing water, and increasing solubility of modern surfactant mixtures, allows the water to run off the dishes in a dish rack very quickly. However, most people also rinse the dishes with pure water to make sure to get rid of any soap residue that could affect the taste of the food.[19]

Dishwashing liquid can be a skin irritant and cause hand eczema. Those with “sensitive skin” are advised amongst other things to persuade someone else to do the washing up.[20]

Automatic dishwashing[edit]

Automatic dishwashing involves the use of a dishwashing machine or other apparatus.[4] It is generally chosen through convenience, sanitation, or personal preference.[4] The cleaning is less reliant on the detergent’s surfactants but more reliant on machine’s hot water as well as the detergent’s builders, bleach, and enzymes.[4] Automatic dishwashing detergents’ surfactants generally have less foam to avoid disrupting the machine.[4]

Informal uses[edit]

Reader’s Digest notes its use as an ant killer, weed killer, to help spread water-borne fertilizer, and to wash human hair.[21] Good Housekeeping says it can be used mixed with vinegar to attract and drown fruit flies.[22] Dishwashing detergent has been used to clean mirrors as well as windows.[23]

Active ingredient in opensource bathroom and kitchen cleaner[edit]

Twibright Pling, an open source general purpose cleaner for glazed, plastic, chrome and inox bathroom and kitchen surfaces, published by Twibright Labs, uses dishwashing liquid as one of active ingredients.


Dishwashing liquid can be mixed with water and additional ingredients such as glycerin and sugar to produce a bubble-blowing solution.[24]

Clothes washing[edit]

Dishwashing liquid may be used for cleaning delicate clothing fabrics such as hosiery and lingerie.[25]

Decal application[edit]

Dishwashing liquid is frequently recommended in a dilute solution to make decals and vinyl graphics easier to position when applying.[26][27]

Leak detection[edit]

In industry, dishwashing liquid is also used to inspect pressurized equipment for leaks, such as propane fittings.[28][29] It is used to inspect pneumatic tires for flats, as well as for quality assurance during the installation process, and as a mounting bead lubricant.[30][31][32]

Mortar mix[edit]

It can be used to mix mortar when there is no plasticizer available on the building sites.[33]

Pest deterrent[edit]

Dishwashing liquid has uses as an ingredient in making homemade garden pest deterrents. Oregon State University‘s Cooperative Extension Service notes the use of dishwashing liquid to get rid of spidermites.[34] Dish soap has also been used to deter aphids.[34][35]In some instances, the dish soap may be toxic to plant leaves and cause them to “burn”.[34] Use of soap or dish detergent to help spread pesticide on plants is noted by University of Georgia extension service, but not recommended.[36]

Stain remover[edit]

A solution of dishwashing liquid and water may be used to remove coffee, tea, soda and fruit juice stains from fabrics.[37][38] One dishwashing liquid brand has been used to remove stains from white or lightly-colored cloth napkins.[39]

Treatment for oil-affected birds and other wildlife[edit]

An oiled Gannet being washed

Dishwashing liquid has been used to treat birds affected by oil spills.[40][41] After the Exxon Valdez oil spill in 1989, the International Bird Rescue Research Center received hundreds of cases of dishwashing liquid that were used to clean up birds and other animals contaminated with spilled oil.[42][43][44] More dishwashing liquid was donated during the Deepwater Horizon oil spill to the International Bird Rescue Research Center and the Marine Mammal Center.[45] Some dishwashing soap brands donated to support oiled birds during the Deepwater Horizon spill have received criticism for being petroleum-based.[40]

Dish soap has been tested as an oil-removing agent on polar bear fur in a study by the Alaska Zoo should a spill occur in the Arctic.[46]

from wikipedia