Editing Soap

{{short description|Substance used for cleaning}}
{{other uses}}
{{pp-semi-indef|small=yes}}
[[File:Handmade soap cropped and simplified.jpg|thumb|upright=1.2|A handmade soap bar]]
[[File:Sodium stearate v2.svg|thumb|upright=1.4|Two equivalent images of the chemical structure of [[sodium stearate]], a typical ingredient found in bar soaps]]
[[File:Action of soap on oil.ogv|thumb|upright=1|[[Emulsion#Emulsifiers|Emulsifying]] action of soap on oil]]

'''Soap''' is a [[salt (chemistry)|salt]] of a [[fatty acid]] (sometimes other carboxylic acids) used for cleaning and lubricating products as well as other applications.<ref>{{GoldBookRef |title=Soap |file=S05721 |accessdate=9 August 2010}}</ref> In a domestic setting, soaps, specifically "toilet soaps", are [[surfactant]]s usually used for [[washing]], [[bathing]], and other types of [[housekeeping]]. In industrial settings, soaps are used as [[thickener]]s, components of some [[lubricant]]s, [[emulsifier]]s, and [[catalyst]]s.

Soaps are often produced by mixing fats and oils with a [[Base (chemistry)|base]].<ref>{{cite web|title=What's The Difference Between Soap and Detergent|publisher=cleancult.com|url=https://www.cleancult.com/blog/whats-the-difference-between-soap-and-detergent/|access-date=2019-12-18|archive-date=2019-12-18|archive-url=https://web.archive.org/web/20191218165118/https://www.cleancult.com/blog/whats-the-difference-between-soap-and-detergent/|url-status=live}}</ref> Humans have used soap for millennia; evidence exists for the production of soap-like materials in ancient [[Babylon]] around 2800 BC.<ref>{{cite book |last=Willcox |first=Michael |title=Poucher's Perfumes, Cosmetics and Soaps |publisher=Kluwer Academic Publishers |year=2000 |isbn=978-0-7514-0479-1 |editor=Hilda Butler |edition=10th |location=Dordrecht |page=453 |chapter=Soap |quote=The earliest recorded evidence of the production of soap-like materials dates back to around 2800 BCE in ancient Babylon. |chapter-url=https://books.google.com/books?id=4HI8dGHgeIQC&pg=PA453 |archive-url=https://web.archive.org/web/20160820150103/https://books.google.com/books?id=4HI8dGHgeIQC&pg=PA453 |archive-date=2016-08-20 |url-status=live}}</ref>

== Types ==
[[File:Decorative Soaps.jpg|thumb|right|A collection of decorative bar soaps, as often found in [[hotel]]s]]

===Toilet soaps===
[[File:Micelle.svg|thumb|upright=1|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).]]
In a domestic setting, "soap" usually refers to what is technically called a toilet soap, used for household and personal cleaning. Toilet soaps are salts of fatty acids with the general formula ([[Carboxylate ion|RCO<sub>2</sub><sup>−</sup>]])M<sup>+</sup>, where M is [[Sodium|Na]] (sodium) or [[Potassium|K]] (potassium).<ref name=UllSoap/>

When used for cleaning, soap [[solubilize]]s particles and grime, which can then be separated from the article being cleaned. The insoluble oil/fat "dirt" become associated inside [[micelle]]s, tiny spheres formed from soap molecules with polar [[hydrophile|hydrophilic]] (water-attracting) groups on the outside and encasing a [[lipophilicity|lipophilic]] (fat-attracting) pocket, which shields the oil/fat molecules from the water, making them soluble. Anything that is soluble will be washed away with the water. In [[hand washing]], as a surfactant, when lathered with a little water, soap kills [[microorganism]]s by disorganizing their membrane [[lipid bilayer]] and [[Denaturation (biochemistry)|denaturing]] their [[protein]]s.{{Citation needed|date=September 2023}} It also [[emulsifies]] oils, enabling them to be carried away by running water.<ref>{{Cite web|url=http://cool.conservation-us.org/waac/wn/wn23/wn23-3/wn23-304.html|title=A Brief History of Aluminum Stearate as a Component of Paint|last=Tumosa|first=Charles S.|date=2001-09-01|website=cool.conservation-us.org|language=en|access-date=2017-04-05|url-status=live|archive-url=https://web.archive.org/web/20170318085239/http://cool.conservation-us.org/waac/wn/wn23/wn23-3/wn23-304.html|archive-date=2017-03-18}}</ref>

When used in [[hard water]], soap does not lather well but forms [[soap scum]] (related to [[metallic soap]]s, see below).<ref>{{cite book |last1=Holman |first1=John S. |last2=Stone |first2=Phil |title=Chemistry |url=https://books.google.com/books?id=j9auT6Jd_JMC&pg=PA174 |publisher=Nelson Thornes |date=2001 |page=174 |isbn=9780748762392}}</ref>

===Non-toilet soaps===
So-called [[metallic soap]]s are key components of most lubricating [[grease (lubricant)|greases]] and thickeners.<ref name=UllSoap>{{cite encyclopedia |author=Klaus Schumann |author2=Kurt Siekmann |chapter=Soaps |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |year=2005 |publisher=Wiley-VCH |location=Weinheim |doi=10.1002/14356007.a24_247 |isbn=978-3527306732}}</ref> A commercially important example is [[lithium stearate]]. Greases are usually [[emulsion]]s of [[calcium stearate|calcium soap]] or [[lithium soap]] and [[mineral oil]]. Many other metallic soaps are also useful, including those of [[aluminium]], [[sodium]], 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 (material)|lime]] to [[olive oil]], which would produce calcium soaps.<ref>{{cite encyclopedia |author=Thorsten Bartels |display-authors=etal |chapter=Lubricants and Lubrication |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |year=2005 |publisher=Wiley-VCH |location=Weinheim |doi=10.1002/14356007.a15_423 |isbn=978-3527306732}}</ref> Metal soaps are also included in modern artists' [[oil paint]]s formulations as a [[rheology]] modifier.<ref>{{cite web|url=http://cool.conservation-us.org/waac/wn/wn23/wn23-3/wn23-304.html|title=A Brief History of Aluminum Stearate as a Component of Paint|last=S.|first=Tumosa, Charles|date=2001-09-01|website=cool.conservation-us.org|language=en|access-date=2017-03-17|url-status=live|archive-url=https://web.archive.org/web/20170318085239/http://cool.conservation-us.org/waac/wn/wn23/wn23-3/wn23-304.html|archive-date=2017-03-18}}</ref> Metal soaps can be prepared by neutralizing fatty acids with metal oxides:
:2 RCO<sub>2</sub>H + CaO → (RCO<sub>2</sub>)<sub>2</sub>Ca + H<sub>2</sub>O

A cation from an [[organic base]] such as [[ammonium]] can be used instead of a metal; ammonium [[nonanoic acid|nonanoate]] is an ammonium-based soap that is used as an herbicide.<ref name="ammonium">{{cite web |url=https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-031802_01-Nov-06.pdf |title=Ammonium nonanoate (031802) Fact Sheet |website=epa.gov |date=2006-09-21 |access-date=2022-08-15 |archive-date=2022-11-16 |archive-url=https://web.archive.org/web/20221116165514/https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-031802_01-Nov-06.pdf |url-status=live }}</ref>

Another class of non-toilet soaps are [[resin soap]]s, which are produced in the [[paper industry]] by the action of tree rosin with alkaline reagents used to separate cellulose from raw wood. A major component of such soaps is the sodium salt of [[abietic acid]]. Resin soaps are used as emulsifiers.<ref>{{cite book |doi=10.1002/14356007.a23_073 |chapter=Resins, Natural |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Fiebach |first1=Klemens |last2=Grimm |first2=Dieter |isbn=3-527-30673-0 }}</ref>

==Soapmaking==
{{Main article|Soaper}}

The production of toilet soaps usually entails [[saponification]] of [[triglyceride]]s, which are vegetable or animal oils and fats. An alkaline solution (often [[lye]]) induces saponification whereby the triglyceride fats first [[Hydrolysis|hydrolyze]] into salts of fatty acids. [[Glycerol]] (glycerin) is liberated. The glycerin is sometimes left in the soap product as a softening agent, although it is sometimes separated.<ref name="Cavitch, Susan Miller 1994">Cavitch, Susan Miller. ''The Natural Soap Book''. Storey Publishing, 1994 {{ISBN|0-88266-888-9}}.</ref><ref>Garzena, Patrizia, and Tadiello, Marina (2013). ''The Natural Soapmaking Handbook''. [http://www.demetra.com.au/ Online information and Table of Contents] {{webarchive|url=https://web.archive.org/web/20150730033519/http://www.demetra.com.au/ |date=2015-07-30 }}. {{ISBN|978-0-9874995-0-9}}/</ref> Handmade soap can differ from industrially made soap in that an excess of fat or coconut oil beyond that needed to consume the [[alkali]] is used (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 [[Moisturizer|emollient]] is added, such as [[jojoba]] oil or [[shea butter]].<ref>{{cite web |title=The Process of Making Soap |url=http://edtech.mcc.edu/~abaker/comw100/finalproject/process.html |website=edtech.mcc.edu |access-date=8 March 2020 |archive-date=15 July 2019 |archive-url=https://web.archive.org/web/20190715192100/http://edtech.mcc.edu/~abaker/comw100/finalproject/process.html |url-status=dead }}</ref> [[Sand]] or [[pumice]] may be added to produce a [[wikt:scouring|scouring]] soap. The scouring agents serve to remove dead cells from the skin surface being cleaned. This process is called [[exfoliation (cosmetology)|exfoliation]].

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 [[antimicrobial resistance]] in microorganisms.<ref name="AntibacterialABC">{{cite web |url=https://abcnews.go.com/Health/story?id=117985 |title=Antibacterial Soaps Concern Experts |publisher=ABC News |access-date=12 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20141112070010/https://abcnews.go.com/Health/story?id=117985 |archive-date=12 November 2014 |date=2006-01-06}}</ref>

The type of alkali metal used determines the kind of soap product. [[Sodium]] soaps, prepared from [[sodium hydroxide]] (soda lye), are firm, whereas [[potassium]] soaps, derived from [[potassium hydroxide]] (potash lye), 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 [[Grease (lubricant)|greases]].

For making toilet soaps, [[triglyceride]]s (oils and fats) are derived from coconut, olive, or palm oils, as well as [[tallow]].<ref name="Ullmann">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. {{doi|10.1002/14356007.a10_245.pub2}}.</ref> Triglyceride is the chemical name for the [[Ester|triesters]] of fatty acids and [[glycerin]]. Tallow, ''i.e.,'' [[Rendering (animal products)|rendered]] 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 with a high percentage of olive oil.

{| class="wikitable" |
|+ Fatty acid content of various fats used for soapmaking
|-
|+
! !! [[Lauric acid]]!! [[Myristic acid]]!! [[Palmitic acid]]!! [[Stearic acid]]!! [[Oleic acid]]!! [[Linoleic acid]]!! [[Linolenic acid]]
|-
! '''''fats'''''!! C<sub>12</sub> saturated!!C<sub>14</sub> saturated!!C<sub>16</sub> saturated!!C<sub>18</sub> saturated!!C<sub>18</sub> monounsaturated!!C<sub>18</sub> diunsaturated!! C<sub>18</sub> triunsaturated
|-
| [[Tallow]] || style="text-align:right;"| 0 || style="text-align:right;"| 4 || style="text-align:right;"| 28 || style="text-align:right;"| 23 || style="text-align:right;"| 35|| style="text-align:right;"| 2|| style="text-align:right;"| 1
|-
| [[Coconut oil]] || style="text-align:right;"| 48 || style="text-align:right;"| 18 || style="text-align:right;"| 9 || style="text-align:right;"| 3 || style="text-align:right;"| 7|| style="text-align:right;"| 2|| style="text-align:right;"|0
|-
| [[Palm kernel oil]] || style="text-align:right;"| 46 || style="text-align:right;"| 16 || style="text-align:right;"| 8 || style="text-align:right;"| 3 || style="text-align:right;"| 12|| style="text-align:right;"| 2|| style="text-align:right;"|0
|-
| [[Palm oil]] || style="text-align:right;"| 0 || style="text-align:right;"| 1 || style="text-align:right;"| 44 || style="text-align:right;"| 4 || style="text-align:right;"| 37 || style="text-align:right;"| 9|| style="text-align:right;"|0
|-
| [[Laurus nobilis|Laurel oil]] || style="text-align:right;"| 54 || style="text-align:right;"| 0 || style="text-align:right;"| 0 || style="text-align:right;"| 0|| style="text-align:right;"| 15|| style="text-align:right;"| 17|| style="text-align:right;"|0
|-
| [[Olive oil]] || style="text-align:right;"| 0 || style="text-align:right;"| 0 || style="text-align:right;"| 11 || style="text-align:right;"| 2 || style="text-align:right;"| 78|| style="text-align:right;"| 10|| style="text-align:right;"|0
|-
| [[Canola oil]] || style="text-align:right;"| 0 || style="text-align:right;"| 1 || style="text-align:right;"| 3 || style="text-align:right;"| 2 || style="text-align:right;"| 58|| style="text-align:right;"| 9|| style="text-align:right;"|23
|}
{{anchor|Soapmaking|Soap-making}}

==Gallery==
<gallery widths="200" heights="200">
File:African Black Soap.jpg|[[Dudu-Osun]] – a popular type of [[African black soap]]
File:Azul e Branco.JPG|[[Azul e branco soap]]&nbsp;– a bar of blue-white soap
File:Soap P1140887.jpg|Handmade soaps sold at a shop in [[Hyères]], [[France]]
File:Bars of pure Marseille and Aleppo soap, 2024.jpg |Traditional [[Marseille soap]] (left) and [[Aleppo soap]] (right)
File:Soap Shop, Tübingen (2019).jpg|Modern soap shop in [[Tübingen]] (2019)
File:Pouring lye into water to make soap.jpg|[[Lye]] being dissolved in water for soapmaking.
File:Wheel Bearing Grease.jpg|Greases for automotive applications contain soaps.
File:Pexels-pixabay-206299.jpg|Soap on a platter
</gallery>

== History ==
===Proto-soaps in the Ancient world===
[[File:MODOAmigo.jpg|thumb|Twentieth century packaging of Amigo del Obrero (Worker's Friend) soap, part of the [[Museo del Objeto del Objeto]] collection]]
Proto-soaps, which mixed fat and alkali and were used for cleansing, are mentioned in [[Sumer]]ian, [[Babylonia]]n and [[Ancient Egypt|Egyptian]] texts.<ref name=":0">{{Cite journal |date=2024-08-22 |title=An Experimental Exploration of the Earliest Soapmaking |url=https://exarc.net/issue-2024-3/at/experimental-exploration-earliest-soapmaking |journal=EXARC Journal |language=en |issue=EXARC Journal Issue 2024/3 |issn=2212-8956}}</ref><ref name=":1">{{cite podcast
| url=https://exarc.net/podcast/meaning-cleaning | title= The Meaning of Cleaning | website=Exarc.net | publisher=Exarc | host=Jess Shaw | date=2 February 2024 | time= | access-date=16 September 2024}}</ref>

The earliest recorded evidence of the production of soap-like materials dates back to around 2800&nbsp;BC in ancient Babylon.<ref>{{cite book |last=Willcox |first=Michael |title=Poucher's Perfumes, Cosmetics and Soaps |publisher=Kluwer Academic Publishers |year=2000 |isbn=978-0-7514-0479-1 |editor=Hilda Butler |edition=10th |location=Dordrecht |page=453 |chapter=Soap |quote=The earliest recorded evidence of the production of soap-like materials dates back to around 2800 BCE in ancient Babylon. |chapter-url=https://books.google.com/books?id=4HI8dGHgeIQC&pg=PA453 |archive-url=https://web.archive.org/web/20160820150103/https://books.google.com/books?id=4HI8dGHgeIQC&pg=PA453 |archive-date=2016-08-20 |url-status=live}}</ref> A formula for making a soap-like substance was written on a Sumerian clay tablet around 2500 BC. This was produced by heating a mixture of oil and [[wood ash]], the earliest recorded chemical reaction, and used for washing [[woolen]] clothing.<ref name="falbe">{{cite book |last=Veerbek |first=H. |url={{Google Books |SjvtCAAAQBAJ|page=1|plain-url=yes}} |title=Surfactants in Consumer Products |publisher=Springer-Verlag |year=2012 |isbn=9783642715457 |editor=Falbe |editor-first=Jürgen |pages=1–2 |chapter=1 Historical Review |via=Google Books}}</ref>

The [[Ebers Papyrus|Ebers papyrus]] (Egypt, 1550&nbsp;BC) indicates the ancient Egyptians used a soap-like product as a medicine and created this by combining animal fats or vegetable oils with a [[soda ash]] substance called [[trona]].<ref name="falbe" /> Egyptian documents mention a similar substance was used in the preparation of [[wool]] for weaving.{{Citation needed|date=September 2021}}

In the reign of [[Nabonidus]] (556–539&nbsp;BC), a recipe for a soap-like substance consisted of ''uhulu'' [ashes], [[cypress]] [oil] and sesame [seed oil] "for washing the stones for the servant girls".<ref>Noted in {{cite journal |author=Levey, Martin |year=1958 |title=Gypsum, salt and soda in ancient Mesopotamian chemical technology |journal=Isis |volume=49 |issue=3 |pages=336–342 (341) |doi=10.1086/348678 |jstor=226942 |s2cid=143632451}}</ref>

=== True soaps in the Ancient world ===
True soaps, which we might recognise as soaps today, were different to proto-soaps. They foamed, were made deliberately, and could be produced in a hard or soft form because of an understanding of lye sources.<ref name=":1" /> It is uncertain as to who was the first to invent true soap.<ref name=":0" /><ref>{{cite book |last1=Derry |first1=Thomas Kingston |url=https://books.google.com/books?id=mf88HKKYEbQC&dq=origin+of+soap+history&pg=PA265 |title=A Short History of Technology: From the Earliest Times to A. D. 1900 |last2=Williams |first2=Trevor Illtyd |date=1960-01-01 |publisher=Courier Corporation |isbn=9780486274720 |page=265}}</ref>

Knowledge of how to produce true soap emerged at some point between early mentions of proto-soaps and the first century AD.<ref name=":0" /><ref name=":1" /> Alkali was used to clean textiles such as wool for thousands of years<ref>{{Cite magazine |last=Cassidy |first=Cody |date=2020-05-05 |title=Who Discovered Soap? What to Know About the Origins of the Life-Saving Substance |url=https://time.com/5831828/soap-origins/ |access-date=2024-09-16 |magazine=TIME |language=en}}</ref> but soap only forms when there is enough fat, and experiments show that washing wool does not create visible quantities of soap.<ref name=":0" /> Experiments by Sally Pointer show that the repeated laundering of materials used in [[perfume]]-making lead to noticeable amounts of soap forming. This fits with other evidence from [[Mesopotamia]]n culture.<ref name=":0" />

Pliny the Elder, whose writings chronicle life in the first century AD, describes soap as "an invention of the Gauls".<ref>{{Cite web |title=The history of soapmaking |url=https://www.open.edu/openlearn/history-the-arts/history/history-science-technology-and-medicine/history-science/the-history-soapmaking |url-status=live |archive-url=https://web.archive.org/web/20220812172210/https://www.open.edu/openlearn/history-the-arts/history/history-science-technology-and-medicine/history-science/the-history-soapmaking |archive-date=2022-08-12 |access-date=2022-08-21 |website=The history of soapmaking}}</ref> The word {{Lang|la|sapo}}, Latin for soap, has connected to a mythical Mount Sapo, a hill near the River Tiber where animals were sacrificed.<ref>{{Cite book |last=Bognolo |first=Guido |title=Surface Active Agents: Historical Perspectives and Future Developments |pages=5}}</ref> But in all likelihood, the word was borrowed from an early Germanic language and is [[cognate]] with Latin {{Lang|la|sebum}}, "[[tallow]]". It first appears in [[Pliny the Elder]]'s account,<ref>{{cite web |last=Harper |first=Douglas |title=Soap |url=http://www.etymonline.com/index.php?term=soap |archive-url=https://web.archive.org/web/20110208192853/http://www.etymonline.com/index.php?term=soap |archive-date=2011-02-08 |access-date=2022-08-15 |website=etymonline.com}}</ref> ''[[Natural History (Pliny)|Historia Naturalis]]'', which discusses the manufacture of soap from tallow and ashes. There he mentions its use in the treatment of [[Scrofula|scrofulous sores]], as well as among the [[Gauls]] as a dye to redden hair which the men in [[Germania]] were more likely to use than women.<ref>Pliny the Elder, ''[[Natural History (Pliny)|Natural History]]'', [https://penelope.uchicago.edu/Thayer/L/Roman/Texts/Pliny_the_Elder/28*.html#191 XXVIII.191].</ref><ref>[[Martial]], Epigrammata, [http://www.thelatinlibrary.com/martial/mart8.shtml VIII, 33, 20.] {{webarchive|url=https://web.archive.org/web/20130121162318/http://www.thelatinlibrary.com/martial/mart8.shtml|date=2013-01-21}}</ref> The Romans avoided washing with harsh soaps before encountering the milder soaps used by the Gauls around 58&nbsp;BC.<ref name="Foreman">{{cite web |last=Foreman |first=Amanda |date=October 4, 2019 |title=The Long Road to Cleanliness |url=https://www.wsj.com/articles/the-long-road-to-cleanliness-11570196433?mod=e2fb |url-status=live |archive-url=https://web.archive.org/web/20200807091833/https://www.wsj.com/articles/the-long-road-to-cleanliness-11570196433?mod=e2fb |archive-date=August 7, 2020 |access-date=October 6, 2019 |work=www.wsj.com}}</ref> [[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''".<ref>Aretaeus, ''The Extant Works of Aretaeus, the Cappadocian'', ed. and tr. Francis Adams (London) 1856:[https://books.google.com/books?id=v4gIAAAAIAAJ 238 and 496] {{webarchive|url=https://web.archive.org/web/20160609210236/https://books.google.com/books?id=v4gIAAAAIAAJ&printsec=frontcover&hl=it|date=2016-06-09}}, noted in Michael W. Dols, "Leprosy in medieval Arabic medicine" ''Journal of the History of Medicine'' 1979:316 note 9; the Gauls with whom the Cappadocian would have been familiar are those of Anatolian [[Galatia (Roman province)|Galatia]].</ref> 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]].<ref>{{cite journal |last1=De Puma |first1=Richard |title=A Third-Century B.C.E. Etruscan Tomb Group from Bolsena in the Metropolitan Museum of Art. |journal=American Journal of Archaeology |pages=429–40}}</ref> The standard design is a curved blade with a handle, all of which is made of metal.<ref>{{cite book |last1=Padgett |first1=J. Michael |title=Objects of Desire: Greek Vases from the John B. Elliot Collection. |date=2002 |publisher=Record of the Art Museum, Princeton University. |pages=36–48}}</ref>

The 2nd-century AD physician [[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 this period. According to Galen, the best soaps were Germanic, and soaps from Gaul were second best. [[Zosimos of Panopolis]], ''circa'' 300&nbsp;AD, describes soap and soapmaking.<ref>{{cite book |last=Partington |first=James Riddick |url=https://archive.org/details/historyofgreekfi00part/page/307 |title=A History of Greek Fire and Gun Powder |author2=Hall, Bert S |publisher=JHU Press |year=1999 |isbn=978-0-8018-5954-0 |page=[https://archive.org/details/historyofgreekfi00part/page/307 307] |url-access=registration}}</ref>

In the Southern [[Levant]], the ashes from [[Barilla|barilla plants]], such as species of [[Salsola]], saltwort (''[[Seidlitzia rosmarinus]]'') and ''[[Anabasis articulata|Anabasis]]'', were used to make [[potash]].<ref>[[Zohar Amar]], ''Flora of the Bible'', Jerusalem 2012, s.v. '''ברית''', p. 216 (note 34) {{OCLC|783455868}}.</ref><ref>{{cite book |last=Abu-Rabiʻa |first=ʻAref |url=https://www.berghahnbooks.com/title/AbuRabiaBedouin |title=Bedouin Century: Education and Development among the Negev Tribes in the Twentieth Century |date=2001 |location=New York |pages=47–48 |language=en |oclc=47119256 |access-date=2019-08-22 |archive-url=https://web.archive.org/web/20190725005846/http://www.berghahnbooks.com/title/AbuRabiaBedouin |archive-date=2019-07-25 |url-status=live}}</ref> Traditionally, olive oil was used instead of animal lard throughout the Levant, which was boiled in a copper cauldron for several days.<ref name="Cohen1989">{{cite book |last=Cohen |first=Amnon |title=Economic Life in Ottoman Jerusalem |date=1989 |publisher=[[Cambridge University Press]] |isbn=0521365511 |location=Cambridge |page=81 |language=en}}</ref> As the boiling progresses, alkali ashes and smaller quantities of [[quicklime]] are added and constantly stirred.<ref name="Cohen1989" /> 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 two 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]] leaves, [[lavender]], [[germander]], etc.

===Ancient China===
A detergent similar to soap was manufactured in ancient China from the seeds of ''[[Gleditsia sinensis]]''.<ref name="Jones">{{cite book |author=Jones, Geoffrey |title=Beauty Imagined: A History of the Global Beauty Industry |date=2010 |publisher=Oxford University Press |isbn=978-0-19-160961-9 |chapter=Cleanliness and Civilization |chapter-url=https://books.google.com/books?id=qki6zZ4aWd0C&pg=PP101 |archive-url=https://web.archive.org/web/20160507004012/https://books.google.com/books?id=qki6zZ4aWd0C&pg=PP101 |archive-date=2016-05-07 |url-status=live}}</ref> Another traditional detergent is a mixture of pig pancreas and plant ash called ''zhuyizi'' ({{zh|s=猪胰子|t=豬胰子|p=zhūyízǐ}}). Soap made of animal fat did not appear in China until the modern era.<ref name="Benn">{{cite book |author=Benn, Charles |url=https://books.google.com/books?id=ile3jSveb4sC&pg=PA116 |title=Everyday Life in the Tang Dynasty |publisher=Oxford University Press |year=2002 |isbn=978-0-19-517665-0 |page=116 |archive-url=https://web.archive.org/web/20160505002603/https://books.google.com/books?id=ile3jSveb4sC&pg=PA116 |archive-date=2016-05-05 |url-status=live}}</ref> Soap-like detergents were not as popular as ointments and creams.<ref name="Jones" />

=== Islamic Golden Age ===
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]] (c. 865–925), 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 (material)|lime]]. Soap was exported from Syria to other parts of the [[Muslim world]] and to Europe.<ref name="hassan">[[Ahmad Y. al-Hassan]] (2001), [https://books.google.com/books?id=h2g1qte4iegC&pg=PA73 ''Science and Technology in Islam: Technology and applied sciences'', pages 73–74]. {{webarchive|url=https://web.archive.org/web/20171209061203/https://books.google.com/books?id=h2g1qte4iegC&pg=PA73|date=2017-12-09}}, [[UNESCO]].</ref>

A 12th-century document describes the process of soap production.<ref>BBC ''Science and Islam'' Part 2, Jim Al-Khalili. BBC Productions. Accessed 30 January 2012.</ref> 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 Middle East had become a major cottage industry, with sources in [[Nablus]], [[Fes]], [[Damascus]], and [[Aleppo]].{{Citation needed|date=April 2023}}

===Medieval Europe===
Soapmakers in [[Naples]] were members of a [[guild]] in the late sixth century (then under the control of the [[Eastern Roman Empire]]),<ref>footnote 48, p. 104, ''Understanding the Middle Ages: the transformation of ideas and attitudes in the Medieval world'', Harald Kleinschmidt, illustrated, revised, reprint edition, Boydell & Brewer, 2000, {{ISBN|0-85115-770-X}}.</ref> and in the eighth century, soap-making was well known in Italy and Spain.<ref name="Related Lime Soap Dispersants 1996, p. 632">Anionic and Related Lime Soap Dispersants, Raymond G. Bistline Jr., in ''Anionic Surfactants: Organic Chemistry'', Helmut Stache, ed., Volume 56 of Surfactant science series, CRC Press, 1996, chapter 11, p. 632, {{ISBN|0-8247-9394-3}}.</ref> 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.<ref>[http://www.soap-flakes.com/history.html www.soap-flakes.com] {{webarchive|url=https://web.archive.org/web/20150526035507/http://www.soap-flakes.com/history.html|date=2015-05-26}}. soap-flakes.com. Retrieved on 2015-10-31.</ref> 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.<ref>{{cite book |last=Robinson |first=James Harvey |url=http://www.fordham.edu/halsall/source/carol-devillis.html |title=Readings in European History: Vol. I |publisher=Ginn and co |year=1904 |archive-url=https://web.archive.org/web/20090925094733/http://www.fordham.edu/halsall/source/carol-devillis.html |archive-date=2009-09-25 |url-status=live}}</ref>

In Europe, soap in the 9th century was produced from animal fats and had an unpleasant smell. This changed when olive oil began to be used in soap formulas instead, after which much of Europe's soap production moved to the Mediterranean olive-growing regions.<ref name="Springer">{{cite book |title=A History of Technology, Volume 2 |publisher=Clarendon Press |year=1954 |isbn=9780198581062 |editor=Charles Springer |pages=355–356}}</ref> Hard toilet soap was introduced to Europe by Arabs and gradually spread as a luxury item. It was often perfumed.<ref name="hassan" /><ref name="Springer" />

By the 15th century, the manufacture of soap in [[Christendom]] often took place on an industrial scale, with sources in [[Antwerp]], [[Castile (historical region)|Castile]], [[Marseille]], [[Naples]] and [[Venice]].<ref name="Related Lime Soap Dispersants 1996, p. 632" />

===16th–17th century===
In France, by the second half of the 16th century, the semi-industrialized professional manufacture of soap was concentrated in a few centers of [[Provence]]—[[Toulon]], [[Hyères]], and [[Marseille]]—which supplied the rest of France.<ref>{{cite journal |author=Nef, John U. |year=1936 |title=A Comparison of Industrial Growth in France and England from 1540 to 1640: III |journal=The Journal of Political Economy |volume=44 |issue=5 |pages=643–666 (660ff.) |doi=10.1086/254976 |jstor=1824135 |s2cid=222453265}}</ref> In Marseilles, by 1525, production was concentrated in at least two factories, and soap production at Marseille tended to eclipse the other Provençal centers.<ref>Barthélemy, L. (1883) "La savonnerie marseillaise", noted by Nef 1936:660 note 99.</ref>

English manufacture tended to concentrate in London.<ref>Nef 1936:653, 660.</ref> The demand for high-quality hard soap was significant enough during the Tudor period that barrels of ashes were imported for the manufacture of soap.<ref name=":1" />

Finer soaps were later produced in Europe from the 17th 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'.<ref>Keith Thomas, 'Noisomeness,' ''London Review of Books'', Vol. 42, No. 14, 16 July 2020.</ref>

During the [[Stuart Restoration|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.<ref>{{cite web |title=The Soap Tax |url=http://archive.spectator.co.uk/article/27th-april-1833/14/the-soap-tax |url-status=live |archive-url=https://web.archive.org/web/20170324084455/http://archive.spectator.co.uk/article/27th-april-1833/14/the-soap-tax |archive-date=24 March 2017 |access-date=23 March 2017 |website=The Spectator Archive |publisher=The Spectator, London}}</ref><ref>{{cite web |title=Repeal of the Soap Tax |url=https://api.parliament.uk/historic-hansard/commons/1838/apr/03/repeal-of-the-soap-tax |url-status=live |archive-url=https://web.archive.org/web/20170324084015/http://hansard.millbanksystems.com/commons/1838/apr/03/repeal-of-the-soap-tax |archive-date=24 March 2017 |access-date=23 March 2013 |date=3 April 1838 |website=[[Hansard|Parliamentary Debates (Hansard)]] }}</ref><ref>{{cite book |last1=Hansard |first1=Thomas Curson |title=Hansard's Parliamentary Debates |date=1864 |publisher=Forgotten Books |isbn=9780243121328 |location=Uxbridge, England |pages=363–374}}</ref>

===Modern period===
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.<ref>{{cite book |last=McNeil |first=Ian |url=https://books.google.com/books?id=uxsOAAAAQAAJ&pg=PA203 |title=An Encyclopaedia of the History of Technology |publisher=Taylor & Francis |year=1990 |isbn=978-0-415-01306-2 |pages=2003–205 |archive-url=https://web.archive.org/web/20160505145316/https://books.google.com/books?id=uxsOAAAAQAAJ&pg=PA203 |archive-date=2016-05-05 |url-status=live}}</ref> 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]].<ref>{{Cite web |last=Ahveninen |first=Anna |date=2020-03-31 |title=Hand sanitiser or soap: making an informed choice for COVID-19 |url=https://www.science.org.au/curious/people-medicine/hand-sanitiser-or-soap-making-informed-choice-covid-19 |url-status=live |archive-url=https://web.archive.org/web/20200805233531/https://www.science.org.au/curious/people-medicine/hand-sanitiser-or-soap-making-informed-choice-covid-19 |archive-date=2020-08-05 |access-date=2020-08-04 |website=Curious |language=en}}</ref>

<gallery widths="200px" heights="200px">
File:Dobbins' medicated toilet soap, advertising, 1869.jpg|Advertising for Dobbins' medicated toilet soap
File:Palmolive soap 1922 advertisement ladies home journal.jpeg|A 1922 magazine advertisement for [[Colgate-Palmolive|Palmolive Soap]]
File:Liquid antibacterial soap.jpg|Liquid soap
File:Pexels-pixabay-433624.jpg|A soap dispenser
</gallery>

[[File:langtry cartoon.png|thumb|upright|Caricature of [[Lillie Langtry]], from ''[[Punch (magazine)|Punch]]'', Christmas 1890: The soap box on which she sits reflects her endorsements of cosmetics and soaps.]]
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]].<ref name="Foreman" /> [[Andrew Pears]] started making a high-quality, transparent soap, [[Pears (soap)|Pears soap]], in 1807 in London.<ref>{{cite book |author=Pears, Francis |url=https://books.google.com/books?id=yFlJAAAAYAAJ&pg=PA100 |title=The Skin, Baths, Bathing, and Soap |publisher=The author |year=1859 |pages=100– |archive-url=https://web.archive.org/web/20160504074628/https://books.google.com/books?id=yFlJAAAAYAAJ&pg=PA100 |archive-date=2016-05-04 |url-status=live}}</ref> His son-in-law, [[Thomas J. Barratt]], became the brand manager (the first of its kind) for Pears in 1865.<ref>{{Cite book |last=Glenday |first=Craig |url=https://archive.org/details/guinnessworldrec0000unse_r3e7/page/200 |title=Guinness World Records 2014 |year=2013 |isbn=9781908843159 |pages=[https://archive.org/details/guinnessworldrec0000unse_r3e7/page/200 200]|publisher=Guinness World Records Limited }}</ref> In 1882, Barratt recruited English actress and socialite [[Lillie Langtry]] to become the poster-girl for Pears soap, making her the first celebrity to endorse a commercial product.<ref>{{cite news |title=When Celebrity Endorsers Go Bad |newspaper=The Washington Post |url=https://www.washingtonpost.com/archive/opinions/2002/02/03/when-celebrity-endorsers-go-bad/260776e6-d38c-4319-b683-eb466c499dce/ |url-status=live |access-date=2 March 2022 |archive-url=https://web.archive.org/web/20221116081428/https://www.washingtonpost.com/archive/opinions/2002/02/03/when-celebrity-endorsers-go-bad/260776e6-d38c-4319-b683-eb466c499dce/ |archive-date=16 November 2022 |quote=British actress Lillie Langtry became the world's first celebrity endorser when her likeness appeared on packages of Pears Soap.}}</ref><ref>{{cite book |last1=Richards |first1=Jef I. |title=A History of Advertising: The First 300,000 Years |date=2022 |publisher=Rowman & Littlefield |page=286}}</ref>

[[William Gossage]] produced low-priced, good-quality soap from the 1850s. [[Robert Spear Hudson (soap)|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 Lever|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===
Liquid soap was invented in the nineteenth century; in 1865, William Sheppard patented a liquid version of soap.<ref>{{cite patent|country=US|number=49561|title=Improved liquid soap|status=patent|gdate=1865-08-22|invent1=Sheppard, William}}</ref> In 1898, B.J. Johnson developed a soap derived from palm and olive oils; his company, the [[Colgate-Palmolive#History|B.J. Johnson Soap Company]], introduced "[[Palmolive (soap)|Palmolive]]" brand soap that same year.<ref>{{Cite web |last=Prigge |first=Matthew |date=2018-01-25 |title=The Story Behind This Bar of Palmolive Soap |url=https://www.milwaukeemag.com/story-behind-this-bar-of-palmolive-soap/ |url-status=live |archive-url=https://web.archive.org/web/20180125175123/https://www.milwaukeemag.com/story-behind-this-bar-of-palmolive-soap/ |archive-date=2018-01-25 |access-date=2019-06-27 |website=Milwaukee Magazine |language=en-US}}</ref> This new brand of soap became popular rapidly, and to such a degree that B.J. Johnson Soap Company changed its name to [[Colgate-Palmolive|Palmolive]].<ref>{{cite web |title=Colgate-Palmolive Company History: Creating Bright Smiles for 200 Years |url=http://www.colgate.com/app/Colgate/US/Corp/History/1806.cvsp |url-status=live |archive-url=https://web.archive.org/web/20060502094906/http://www.colgate.com/app/Colgate/US/Corp/History/1806.cvsp |archive-date=2 May 2006 |access-date=17 October 2012 |publisher=[[Colgate-Palmolive]] Company}}</ref>

In the early 1900s, other companies began to develop their own liquid soaps. Such products as [[Pine-Sol]] and [[Tide (brand)|Tide]] 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 (laundry)|washboard]].<ref>{{cite web |title=The History of Liquid Soap |url=http://www.blueaspenoriginals.org/liquid-soap.html |url-status=live |archive-url=https://web.archive.org/web/20121201140608/http://www.blueaspenoriginals.org/liquid-soap.html |archive-date=1 December 2012 |access-date=17 October 2012 |publisher=Blue Aspen Originals}}</ref>

== See also ==

=== Soap-related ===
{{div col|colwidth=22em}}
* [[Antibiotic misuse]]
* [[Dishwashing soap]]
* [[Foam]]
* [[List of cleaning products]]
* [[Hand washing]]
* [[Palm oil]]
* [[Soap bubble]]
* [[Soap dish]]
* [[Soap dispenser]]
* [[Soap plant]]
* [[Soap substitute]]
* [[Soapwort]]
* [[Shampoo]]
* [[Shower gel]]
* [[Toothpaste]]
* [[Soap made from human corpses]]
{{div col end}}

==References==
{{Reflist|30em}}

==Further reading==
* {{Cite journal |last1=Kunatsa |first1=Yvonne |last2=Katerere |first2=David R. |year=2021 |title=Checklist of African Soapy Saponin-Rich Plants for Possible Use in Communities' Response to Global Pandemics |journal=Plants |volume=10 |issue=5 |pages=842 |doi=10.3390/plants10050842 |doi-access=free |issn=2223-7747 |pmc=8143558 |pmid=33922037 |quote=Modern toilet soaps and detergents trace their origin to the ancient use of plants, commonly referred to as soapy plants, which possess foaming ability when they are agitated in water.}}
* {{cite book|year=1895|last1=Carpenter|first1=William Lant|last2=Leask|first2=Henry|title=A treatise on the manufacture of soap and candles, lubricants and glycerin|url={{Google books|SD43AAAAMAAJ|A treatise on the manufacture of soap and candles, lubricants and glycerin|page=PR3|plainurl=yes}}}} Free ebook at [[Google Books]].
* Donkor, Peter (1986). ''[https://www.slideshare.net/v2zq/yze151 Small-Scale Soapmaking: A Handbook]''. Ebook online at [[SlideShare]]. {{ISBN|0-946688-37-0}}.
* Dunn, Kevin M. (2010). ''Scientific Soapmaking: The Chemistry of Cold Process''. Clavicula Press. {{ISBN|978-1-935652-09-0}}.
* Garzena, Patrizia, and Marina Tadiello (2004). ''Soap Naturally: Ingredients, methods and recipes for natural handmade soap''. [http://www.soap-naturally.com/ Online information and Table of Contents]. {{ISBN|978-0-9756764-0-0}}/
* Garzena, Patrizia, and Marina Tadiello (2013). ''The Natural Soapmaking Handbook''. [http://www.demetra.com.au/ Online information and Table of Contents]. {{ISBN|978-0-9874995-0-9}}/
* Mohr, Merilyn (1979). ''The Art of Soap Making''. A Harrowsmith Contemporary Primer. Firefly Books. {{ISBN|978-0-920656-03-7}}.
* Spencer, Bob; Practical Action (2005). ''[https://www.countryfarm-lifestyles.com/support-files/soapmaking-how-to-make-soap.pdf SOAPMAKING] {{webarchive |url=https://web.archive.org/web/20200921125507/https://www.countryfarm-lifestyles.com/support-files/soapmaking-how-to-make-soap.pdf |date=2020-09-21}}''. Ebook online.
* {{cite encyclopedia |title=Soap |url=https://books.google.com/books?id=epNJAAAAIAAJ&dq=Spons'%20Workshop%20Receipts&pg=PA143 |encyclopedia=Workshop Receipts, for Manufacturers and Scientific Amateurs |location=London |publisher=E. & F. N. Spon |year=1909 |volume=IV ''Rain Water to Wire Ropes'' |oclc=1159761115 |pages=143–179 |ref={{harvid|Spon, IV|1909}}}}
* Thomssen, E. G., Ph.D. (1922). ''[http://www.gutenberg.org/ebooks/34114 Soap-Making Manual]''. Free ebook at [[Project Gutenberg]].

==External links==
{{Sister project links| wikt=no | commons=Category:Soap | b=no | n=no | q=Soap | s=no | v=no | voy=no | species=no | d=no}}
* {{cite EB1911|wstitle=Soap|volume=25|pp=296–299}}
* [http://www.soaphistory.net/ History of Soap making] – SoapHistory

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[[Category:Anionic surfactants]]
[[Category:Cleaning products]]
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