Soap is a salt
of a fatty acid
used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactant
s usually used for washing
, and other types of housekeeping
. In industrial settings, soaps are used as thickener
s, components of some lubricant
s, and precursors to catalyst
When used for cleaning, soap solubilizes
particles and grime, which can then be separated from the article being cleaned. In hand washing
, as a surfactant, when lathered with a little water, soap kills microorganism
s by disorganizing their membrane lipid bilayer
s. It also emulsifies
oils, enabling them to be carried away by running water.
Soap is created by mixing fats and oils with a base
, as opposed to detergent
which is created by combining chemical compounds in a mixer.
Humans have used soap for millennia. Evidence exists of the production of soap-like materials in around 2800 BC in ancient Babylon
Types of soaps
Since they are salts of fatty acids, soaps have the general formula (RCO2−
(Where R is an alkyl
, M is a metal
and n is the charge of the cation
). The major classification of soaps is determined by the identity of Mn+
. When M is Na
, the soaps are called toilet soaps, used for handwashing. Many metal dication
, and others) give metallic soap
. When M is Li
, the result is lithium soap
(e.g., lithium stearate
), which is used in high-performance greases
Soaps are key components of most lubricating greases
and thickeners. Greases are usually emulsion
s of calcium soap
or lithium soap and mineral oil
. Many other metallic soaps are also useful, including those of aluminium
, and mixtures thereof. 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
Metal soaps are also included in modern artists' oil paint
s formulations as a rheology
Production of metallic soaps
Most metal soaps are prepared by neutralization of purified fatty acids:
In a domestic setting, "soap" usually refers to what is technically called a toilet soap, used for household and personal cleaning. When used for cleaning, soap solubilizes particles and grime, which can then be separated from the article being cleaned.
The insoluble oil/fat molecules become associated inside micelle
s, 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.
Production of toilet soaps
The production of toilet soaps usually entails saponification
s, which are vegetable or animal oils and fats. An alkaline solution (often lye
or sodium hydroxide
) induces saponification whereby the triglyceride fats first hydrolyze
into salts of fatty acids. Glycerol
(glycerin) is liberated. The glycerin can remain in the soap product as a softening agent, although it is sometimes separated.
[Cavitch, Susan Miller. ''The Natural Soap Book''. Storey Publishing, 1994 .]
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
For making toilet soaps, triglyceride
s (oils and fats) are derived from coconut, olive, or palm oils, as well as tallow
[David J. Anneken, Sabine Both, Ralf Christoph, Georg Fieg, Udo Steinberner, Alfred Westfechtel "Fatty Acids" in Ullmann's ''Encyclopedia of Industrial Chemistry'' 2006, Wiley-VCH, Weinheim. ]
Triglyceride is the chemical name for the triester
s of fatty acids and glycerin
. Tallow, ''i.e.,'' rendered
beef fat, is the most available triglyceride from animals. Each species offers quite different fatty acid content, resulting in soaps of distinct feel. The seed oils give softer but milder soaps. Soap made from pure olive oil
, sometimes called Castile soap
or Marseille soap
, is reputed for its particular mildness. The term "Castile" is also sometimes applied to soaps from a mixture of oils, but a high percentage of olive oil.
Ancient Middle East
The earliest recorded evidence of the production of soap-like materials dates back to around 2800 BC in ancient Babylon
. 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 Egypt
ians bathed regularly and combined animal and vegetable oils with alkaline salts to create a soap-like substance. Egyptian documents mention a similar substance was used in the preparation of wool
In the reign of Nabonidus
(556–539 BC), a recipe for soap consisted of ''uhulu'' shes cypress il
and sesame eed oil
"for washing the stones for the servant girls".
In ancient Palestine
, the ashes from barilla plants
, such as species of Salsola
, saltwort (''Seidlitzia rosmarinus
'') and ''Anabasis
'', were used in soap production, known as potash
. Soap made from potash (a concentrate of burnt wood or vegetable ashes mixed with lard or olive oil) is alkaline. If animal lard were used, it was heated and kept lukewarm (not boiling hot; neither cold). Lard, collected from suet
, needed to be rendered and strained before being used with ashes (with the recommended consistency of 1 cup of lard to 3/8 cup of concentrated ash water). Traditionally, olive oil was used instead of animal lard throughout the Levant
, which was boiled in a copper cauldron for several days.
As the boiling progresses, alkali ashes and smaller quantities of quicklime
were added, and constantly stirred.
In the case of lard, it required constant stirring while kept lukewarm until it began to trace. Once it began to thicken, the brew was poured into a mold and left to cool and harden for 2 weeks. After hardening, it was cut into smaller cakes. Aromatic herbs were often added to the rendered soap to impart their fragrance, such as yarrow
, etc. The ancient method here described is still in use in the production of Nabulsi soap
The word ''sapo'', Latin for soap, likely was borrowed from an early Germanic language and is cognate
with Latin ''sebum'', "tallow
". It first appears in Pliny the Elder
's account, ''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 Gaul
s and Germans
were more likely to use it than their female counterparts. The Romans avoided washing with harsh soaps before encountering the milder soaps used by the Gauls around 58 BC.
Aretaeus of Cappadocia
, writing in the 2nd century AD, observes among "Celts, which are men called Gauls, those alkaline substances that are made into balls ..
called ''soap''". 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.
Zosimos of Panopolis
, ''circa'' 300 AD, describes soap and soapmaking.
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 AD. According to Galen, the best soaps were Germanic, and soaps from Gaul were second best.
A detergent similar to soap was manufactured in ancient China from the seeds of Gleditsia sinensis
Another traditional detergent is a mixture of pig pancreas and plant ash called ''zhuyizi'' (). True soap, made of animal fat, did not appear in China until the modern era.
Soap-like detergents were not as popular as ointments and creams.
Islamic Middle East
Hard toilet soap with a pleasant smell was produced in the Middle East
during the Islamic Golden Age
, when soap-making became an established industry. Recipes for soap-making are described by Muhammad ibn Zakariya al-Razi
(854–925), who also gave a recipe for producing glycerine
from olive oil
. In the Middle East, soap was produced from the interaction of fatty oil
s and fat
s with alkali
. In Syria
, soap was produced using olive oil together with alkali and lime
. Soap was exported from Syria to other parts of the Muslim world
and to Europe.
[Ahmad Y. al-Hassan (2001)]
''Science and Technology in Islam: Technology and applied sciences'', pages 73-74
A 12th-century Islamic document describes the process of soap production. It mentions the key ingredient, alkali
, which later became 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
, and Aleppo
Soapmakers in Naples
were members of a guild
in the late sixth century (then under the control of the Eastern Roman Empire
), and in the eighth century, soap-making was well known in Italy and Spain. 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. 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.
In Europe, soap in the 9th century was produced from animal fats and had an unpleasant smell. Hard toilet soap with a pleasant smell was later imported from the Middle East.
By the 15th century, the manufacture of soap in the Christendom
had become virtually industrialized, with sources in Antwerp
In France, by the second half of the 15th century, the semi-industrialized professional manufacture of soap was concentrated in a few centers of Provence
, and Marseille
—which supplied the rest of France. In Marseilles, by 1525, production was concentrated in at least two factories, and soap production at Marseille tended to eclipse the other Provençal centers. English manufacture tended to concentrate in London.
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 1634 Charles I granted the newly formed Society of Soapmakers a monopoly in soap production who produced certificates from ‘foure Countesses, and five Viscountesses, and divers other Ladies and Gentlewomen of great credite and quality, besides common Laundresses and others’, testifying that ‘the New White Soap washeth whiter and sweeter than the Old Soap’.
Industrially manufactured ''bar soaps'' became available in the late 18th century, as advertising campaigns in Europe and America promoted popular awareness of the relationship between cleanliness and health. 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
File:Dobbins' medicated toilet soap, advertising, 1869.jpg|Advertising at Dobbins' medicated toilet soap
File:Palmolive soap 1922 advertisement ladies home journal.jpeg|A 1922 magazine advertisement for Palmolive Soap
File:Liquid antibacterial soap.jpg|Liquid soap
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. In 1790, Nicolas Leblanc
discovered how to make alkali from common salt
started making a high-quality, transparent soap in 1807 in London
. His son-in-law, Thomas J. Barratt
, opened a factory in Isleworth
During the Restoration era
(February 1665 – August 1714) a soap tax was introduced in England, which meant that until the mid-1800s, soap was a luxury, used regularly only by the well-to-do. The soap manufacturing process was closely supervised by revenue officials who made sure that soapmakers' equipment was kept under lock and key when not being supervised. Moreover, soap could not be produced by small makers because of a law that stipulated that soap boilers must manufacture a minimum quantity of one imperial ton at each boiling, which placed the process beyond the reach of the average person. The soap trade was boosted and deregulated when the tax was repealed in 1853.
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 the sale of bar soap and distribution of product sample
s. 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
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 derived from palm and olive oils; his company, the B.J. Johnson Soap Company
, introduced "Palmolive
" brand soap that same year. This new brand of soap became popular rapidly, and to such a degree that B.J. Johnson Soap Company changed its name to Palmolive
In the early 1900s, other companies began to develop their own liquid soaps. Such products as Pine-Sol
appeared on the market, making the process of cleaning things other than skin, such as clothing, floors, and bathrooms, much easier.
Liquid soap also works better for more traditional or non-machine washing methods, such as using a washboard
Soap-making for hobbyists
A variety of methods are available for hobbyists to make soap. Most soapmakers use processes where the glycerol remains in the product, and the saponification continues for many days after the soap is poured into molds
. The glycerol 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 glycerol left in acts as a moisturizing agent. However, the glycerine also makes the soap softer. The addition of glycerol and processing of this soap produces glycerin soap
. Superfatted soap is more skin-friendly than one without extra fat, although it can leave a "greasy" feel. Sometimes, an emollient
is added, such as jojoba
oil or shea butter
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
To make antibacterial
soap, compounds such as triclosan
can be added. There is some concern that use of antibacterial soaps and other products might encourage antimicrobial resistance
Image:Azul e Branco.JPG|Azul e branco soap – a bar of blue-white soap
Image:Soap P1140887.jpg|Handmade soaps sold at a shop in Hyères, France
Image:Savon de Marseille.jpg|Traditional Marseille soap
Image:Soap Shop, Tübingen (2019).jpg|Modern soap shop in Tübingen (2019)
File:Pouring lye into water to make soap.jpg|The lye is dissolved in water.
Personal use soap
* African black soap
, popular in West Africa
* Aleppo soap
, popular in Syria
* Castile soap
, popular in Spain
* Lava (soap)
, cleaning hands from industrial grease and dirt
* Marseille soap
, popular in France
* Nabulsi soap
, popular in the West Bank
* Saltwater soap
, used to wash in seawater
* Shaving soap
, used for shaving
* Vegan soap
, made without use of animal byproducts
* Antibiotic misuse
* Dishwashing soap
* List of cleaning products
* Hand washing
* Soap bubble
* Soap dish
* Soap dispenser
* Soap plant
* Soap substitute
* Shower gel
* Soap made from human corpses
* Free ebook at Google Books
* Donkor, Peter (1986). Small-Scale Soapmaking: A Handbook
'. Ebook online at SlideShare
* Dunn, Kevin M. (2010). ''Scientific Soapmaking: The Chemistry of Cold Process''. Clavicula Press. .
* Garzena, Patrizia, and Marina Tadiello (2004). ''Soap Naturally: Ingredients, methods and recipes for natural handmade soap''Online information and Table of Contents
* Garzena, Patrizia, and Marina Tadiello (2013). ''The Natural Soapmaking Handbook''Online information and Table of Contents
* Mohr, Merilyn (1979). ''The Art of Soap Making''. A Harrowsmith Contemporary Primer. Firefly Books. .
* Spencer, Bob; Practical Action (2005). SOAPMAKING
'. Ebook online.
* Thomssen, E. G., Ph.D. (1922). Soap-Making Manual
'. Free ebook at Project Gutenberg