Stainless steel soap is a piece of stainless steel, in the form of a soap bar or other hand-held shape. Its purported purpose is to neutralize or reduce strong odors such as those from handling garlic,

onion An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onio ...

, durian, guava,

salami Salami ( ) is a cured sausage consisting of fermented and air-dried meat, typically pork. Historically, salami was popular among Southern, Eastern, and Central European peasants because it can be stored at room temperature for up to 45 days ...

, or

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

. No published scientific studies are known to have been conducted on the efficacy of these soaps, for which serious doubts have been raised.

Proposed mechanism

*The chemistry of garlic The characteristic taste and odor of garlic is due to an oily, slightly yellow organosulfur compound S-Allyl prop-2-ene-1-sulfinothioate, commonly called

Allicin Allicin is an organosulfur compound obtained from garlic, a species in the family Alliaceae. It was first isolated and studied in the laboratory by Chester J. Cavallito and John Hays Bailey in 1944. When fresh garlic is chopped or crushed, th ...

. Fresh garlic has little odor until it is chopped or crushed. Allicin is produced from

alliin Alliin is a sulfoxide that is a natural constituent of fresh garlic. It is a derivative of the amino acid cysteine. When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma ...

(a derivative of the amino acid cysteine) by the enzyme

alliinase In enzymology, an alliin lyase () is an enzyme that catalyzes the chemical reaction :an ''S''-alkyl-L-cysteine ''S''-oxide \rightleftharpoons an alkyl sulfenate + 2-aminoacrylate Hence, this enzyme has one substrate, ''S''-alkyl-L-cysteine ...

. Allicin is unstable and breaks down to form other sulfur compounds such as diallyl sulfides. These compounds contribute to the smell of fresh garlic. When on the hands these sulfur compounds can further degrade into other sulfur compounds, including sulfuric acid, in the presence of water. *The chemistry of stainless steel Steel is an alloy made up of

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

mixed with

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

. Stainless steel is composed of steel mixed with other elements such as chromium, nickel, molybdenum, etc. Chromium is added to make it resistant to rust. Stainless steels that are corrosion and oxidation resistant typically need an additional 11% chromium. Nickel is added to increase the corrosion resistance further, and protect it from harsh environmental conditions. Molybdenum may be added to avoid pitting or scarring. The chemical properties of stainless steel can be further improved for specialized uses by adding other elements, e.g. titanium, vanadium and copper. *Possible mechanism Stainless steel contains about 11% chromium which forms a passive oxide film on the surface of the metal, resulting in its corrosion resistance. It is suggested that allicin and the other sulfur compounds (including sulfuric acid) react with the chromium oxide layer, some possibly being

adsorbed Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a ...

onto it. Washing the stainless steel soap in water would remove this layer and with it the smelly sulfur compounds. The oxide film would then reform and the stainless steel soap can be reused. Mark Lorch, Professor of Science Communication and Chemistry at the University of Hull and Joanna Buckley, Materials chemist and science communicator, at the University of Sheffield conducted some " citizen science" in 2016 to test this mechanism but there is no conclusive, rigorous evidence for it.

Usage

Companies that produce stainless steel soaps claim that the odors these foods cause result from sulfur, which turns into sulfuric acid upon washing the hands. The aim of the stainless steel soap is to then bind to the sulfur molecules, thus removing them and the associated smell from the hands. No published scientific studies are known to have been conducted on the efficacy of these soaps, for which serious doubts have been raised.

References

{{Reflist, refs= {{cite journal , last1=Amagase , first1=Harunobu , last2=Petesch , first2=Brenda L. , last3=Matsuura , first3=Hiromichi , last4=Kasuga , first4=Shigeo , last5=Itakura , first5=Yoichi , title=Intake of Garlic and Its Bioactive Components , journal=The Journal of Nutrition , publisher=Oxford University Press (OUP) , volume=131 , issue=3 , year=2001 , issn=0022-3166 , doi=10.1093/jn/131.3.955s , pages=955S–962S, pmid=11238796 , doi-access=free {{cite web , first1=Mark , last1=Lorch , first2=Joanna , last2=Buckley , title=Does stainless steel really get rid of garlic smells? Round 2. – Chemistry Blog , website=Chemistry Blog – A Chat and Waffles Chemistry Blog , date=24 November 2016 , url=http://www.chemistry-blog.com/2016/11/24/does-stainless-steel-really-get-rid-of-garlic-smells-round-2/ , access-date=8 March 2022 {{Cite book , editor-last = Davis , editor-first = Joseph R. , year = 1994 , title = Stainless Steels , location = Materials Park, OH , publisher = ASM International , series = ASM Specialty Handbook , isbn = 9780871705037 , url = https://books.google.com/books?id=OrlG98AHdoAC , access-date = 8 March 2022 , archive-date = 14 April 2021 , archive-url = https://web.archive.org/web/20210414012400/https://books.google.com/books?id=OrlG98AHdoAC , url-status = live {{Cite web , author=Kitchen Daily , url=https://www.huffpost.com/entry/eliminating-garlic-smell_n_1341413, title=Why Does Stainless Steel Erase Garlic's Smell?, date=2012-03-13, website=HuffPost, language=en, access-date=2019-06-20 {{cite journal , last1= Kourounakis , first1=PN , last2=Rekka , first2=EA , title = Effect on active oxygen species of alliin and Allium sativum (garlic) powder , journal = Research Communications in Chemical Pathology and Pharmacology , volume = 74 , issue = 2 , pages = 249–52 , date = November 1991 , pmid = 1667340 {{cite web , title=Does a Bit of Steel Get Rid of That Garlic Smell? , url=https://www.npr.org/templates/story/story.php?storyId=6473350 , work=All Things Considered , first=Jacki , last=Lyden , publisher=NPR , date=2006-11-11 , access-date=8 March 2022 , url-status=live , archive-url=https://web.archive.org/web/20151117031434/http://www.npr.org/templates/story/story.php?storyId=6473350 , archive-date=2015-11-17 {{cite web , url=http://www.wisegeek.com/what-is-stainless-steel-soap.htm , first=Michael , last=Pollick , title=What is Stainless Steel Soap? , date=2012-04-04 , website={{not a typo, wiseGEEK , access-date=8 March 2022 , url-status=live , archive-url=https://web.archive.org/web/20151117030413/http://www.wisegeek.com/what-is-stainless-steel-soap.htm , archive-date=2015-11-17 {{cite web , title=The Chemical Properties of Stainless Steel That Make it Unique , url=https://sciencestruck.com/chemical-properties-of-stainless-steel , website=ScienceStruck , date=18 June 2009 , publisher=Science Struck & Buzzle.com, Inc. , access-date=9 March 2022 {{cite web , date = 8 March 2020 , title = The Stainless Steel Family , location = Brussels, Belgium , author = International Stainless Steel Forum , url = http://www.worldstainless.org/Files/issf/non-image-files/PDF/TheStainlessSteelFamily.pdf , access-date = 8 March 2022 , archive-date = 24 March 2016 , archive-url = https://web.archive.org/web/20160324085201/http://www.worldstainless.org/Files/ISSF/non-image-files/PDF/TheStainlessSteelFamily.pdf , url-status = live Kitchenware Soaps Steel Pseudoscience Steel objects

Proposed mechanism

Usage

See also

References