Category Archives: soap

Shampoo

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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History[edit]

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.

India[edit]

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]

Europe[edit]

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]

Indonesia[edit]

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]

Composition[edit]

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]

Dandruff[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]

All-natural[edit]

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]

Baby[edit]

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.

Animal[edit]

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[edit]

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[edit]

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]

Theory[edit]

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

soap

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.

Molds[edit]

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]