Examine individual changes

'{{Short description|Coating that prevents sticking}} [[File:Blintzes in frying pan.jpg|thumb|right|Food in a non-stick pan]] A '''non-stick surface''' is engineered to reduce the ability of other materials to stick to it. Non-stick cookware is a common application, where the non-stick coating allows food to brown without sticking to the pan. Non-stick is often used to refer to surfaces coated with [[polytetrafluoroethylene]] (PTFE), a well-known brand of which is [[Teflon]]. In the twenty-first century, other coatings have been marketed as non-stick, such as [[Anodizing#Anodized aluminium|anodized aluminium]], [[silica]], [[Cast-iron cookware#Enameled cast iron|enameled cast iron]], and [[Seasoning (cookware)|seasoned cookware]]. ==Types== ===Seasoning=== {{main|Seasoning (cookware)}} [[File:Castiron-skillets.jpg|thumb|Cast iron skillets, before seasoning (left) and after several years of use (right)]] [[File:Belgian waffles cooked in a Krampouz cast-iron waffle iron.JPG|thumb|Commercial waffle iron requiring seasoning]] [[Cast-iron cookware|Cast iron]], [[carbon steel]],<ref>How to Season a Wok- Serious Eats</ref> [[stainless steel]]<ref>{{Cite web|url=https://www.epicurious.com/expert-advice/how-to-turn-stainless-steel-skillet-nonstick-article|title=How to Turn a Stainless Steel Skillet into a Nonstick Pan|date=23 March 2017}}</ref> and cast aluminium cookware{{citation needed|date=December 2020}} may be seasoned before cooking by applying a fat to the surface and heating it to polymerize it. This produces a dry, hard, smooth, [[hydrophobic]] coating, which is non-stick when food is cooked with a small amount of cooking oil or fat. ===Fluoropolymer=== The modern non-stick pans were made using a coating of [[Teflon]] (polytetrafluoroethylene or PTFE). PTFE was invented [[Serendipity|serendipitously]] by [[Roy Plunkett]] in 1938,<ref name="Profile">{{cite web| title= Roy J. Plunkett |url=https://www.sciencehistory.org/historical-profile/roy-j-plunkett|website= [[Science History Institute]]|date=June 2016|access-date=21 February 2018}}</ref><ref name="OH">{{cite web|author=Center for Oral History| title= Roy J. Plunkett |url=https://oh.sciencehistory.org/oral-histories/plunkett-roy-j|website= [[Science History Institute]]|access-date=21 February 2018}}</ref> while working for a joint venture of the [[DuPont]] company. The substance was found to have several unique properties, including very good corrosion-resistance and the lowest coefficient of friction of any substance yet manufactured. PTFE was first used to make seals resistant to the [[uranium hexafluoride]] gas used in development of the [[atomic bomb]] during [[World War II]], and was regarded as a military secret. Dupont registered the Teflon trademark in 1944 and soon began planning for post-war commercial use of the new product.<ref name="IandTmag">{{cite journal|journal=[[Invention and Technology Magazine]]|author=Anne Cooper Funderburg|title=Making Teflon Stick|series=Summer 2000|volume=16|issue=1|url=http://www.inventionandtech.com/content/making-teflon-stick-1|access-date=2015-02-21}}</ref> By 1951 Dupont had developed applications for Teflon in commercial bread and cookie-making; however, the company avoided the market for consumer cookware due to potential problems associated with release of toxic gases if stove-top pans were overheated in inadequately ventilated spaces. While working at [[DuPont]], [[NYU Tandon School of Engineering]] alumnus John Gilbert was asked to evaluate a newly developed material called Teflon. His experiments using the fluorinated polymer as a surface coating for pots and pans helped usher in a revolution in non-stick cookware.<ref>{{cite web|url=http://phys.org/news/2011-07-teflon-super-durable-proteins.html|title=Inspired by teflon, researchers create super durable proteins}}</ref><ref>{{cite web|url=https://issuu.com/spark451/docs/invention_brochure/6|title=Invention, Innovation and Entrepreneurship Begin at the NYU Polytechnic School of Engineering|date=21 April 2014 }}</ref> A few years later, a French engineer had begun coating his fishing gear with Teflon to prevent tangles. His wife Colette suggested using the same method to coat her cooking pans. The idea was successful and a French patent was granted for the process in 1954. The [[Tefal]] company was formed in 1956 to manufacture non-stick pans.<ref name="IandTmag" /> ====PTFE (Teflon)==== [[Polytetrafluoroethylene]] (PTFE) is a synthetic [[fluoropolymer]] used in various applications including non-stick coatings. Teflon is a brand of PTFE, often used as a generic term for PTFE. The metallic substrate is roughened by [[abrasive blasting]], then sometimes [[Thermal spraying|electric-arc sprayed]] with [[stainless steel]].<ref>Nicholas J. Wall, {{patent|US|5069937|"Thermal spraying of stainless steel"}}, 1988</ref><ref>Laurence W. McKeen, ''Fluorinated coatings and finishes handbook'', 2006, p. 117</ref> The irregular surface promotes adhesion of the PTFE and also resists abrasion of the PTFE.<ref>Excalibur brochure, [http://www.whitfordww.com/pdf/literature/Excalibur_2011.pdf PDF]</ref> Then one to seven layers of PTFE are sprayed or rolled on, with a larger number of layers and spraying being better. The number and thickness of the layers and quality of the material determine the quality of the non-stick coating.<ref>{{cite web |url=http://www.cookingforengineers.com/article/326/Whats-In-Your-Non-Stick/print |title=Cooking For Engineers |newspaper=Cookingforengineers.com |access-date= 23 January 2016}}</ref> Better-quality coatings are more durable, and less likely to peel and flake, and keep their non-stick properties for longer. Any PTFE-based coating will rapidly lose its non-stick properties if overheated; all manufacturers recommend that temperatures be kept below, typically, {{Convert|260|C}}.<ref>{{cite web |url=https://www.chemours.com/Teflon/en_US/products/safety/cookware_safety.html |title=Cookware Safety by Teflon nonstick coatings |newspaper=Chemours Web site |access-date= 23 January 2016}}</ref> Utensils used with PTFE-coated pans can scratch the coating if the utensils are harder than the coating; this can be prevented by using non-metallic (usually plastic or wood) cooking tools. ==== Health concerns ==== When pans are overheated beyond approximately 260°C (500°F) the PTFE coating begins to dissociate, releasing [[hydrofluoric acid]] and a variety of [[organofluorine]] compounds which can cause [[polymer fume fever]] in humans and can be lethal to birds. Concerns have been raised over the possible negative effects of using PTFE-coated cooking pans.<ref name="IandTmag" /><ref>{{cite web |url=http://www.teflon.com/Teflon/teflonissafe/keyquestions.html#q2 |archive-url=https://web.archive.org/web/20080117234907/http://www.teflon.com/Teflon/teflonissafe/keyquestions.html#q2 |archive-date=2008-01-17 |title=Safety of Teflon Non-Stick Coatings for Cookware|publisher=[[DuPont]]|access-date=2009-05-06}}</ref><ref>American Cancer Society, [http://www.cancer.org/cancer/cancercauses/othercarcinogens/athome/teflon-and-perfluorooctanoic-acid--pfoa Teflon and Perfluorooctanoic Acid (PFOA)]</ref><ref>{{cite news|last=Tugend|first=Alina|title=Teflon Is Great for Politicians, but Is It Safe for Regular People?|url=https://www.nytimes.com/2006/10/14/business/14shortcuts.html?ref=teflon&_r=0|access-date=15 September 2013|newspaper=New York Times|date=October 14, 2006}}</ref> Processing of PTFE in the past used to include [[Perfluorooctanoic acid|PFOA]] as an emulsifier; however, PFOA is a [[persistent organic pollutant]] and poses both environmental and [[PFOA#Health concerns|health concerns]], and is now being phased out of use in PTFE processing.<ref>Juliet Eilperin: [https://www.washingtonpost.com/wp-dyn/content/article/2006/01/25/AR2006012502041.html ''Harmful Teflon Chemical To Be Eliminated by 2015'']. The Washington Post, 2006-01-26</ref> PFOA is now replaced by the [[GenX]] product manufactured by the DuPont spin-off Chemours, which seems to pose similar health issues as the now banned PFOA.<ref name="EPA-basic">{{cite web |url=https://www.epa.gov/pfas/basic-information-pfas |title=Basic Information on PFAS |author=<!--Not stated--> |date=2018-02-18 |website=PFOA, PFOS and Other PFASs |publisher=U.S. Environmental Protection Agency (EPA) |location=Washington, D.C.}}</ref> ==== Culinary uses and limitations ==== With other types of pans, some [[Cooking oil|oil]] or fat is required to prevent hot food from sticking to the pan's surface. Food does not have the same tendency to stick to a non-stick surface; pans can be used with less, or no oil, and are easier to clean as residues do not stick to the surface. According to writer Tony Polombo, pans that are not non-stick are better for producing pan gravy, because the [[fond]] (the caramelized drippings that stick to the pan when meat is cooked) sticks to them, and can be turned into pan gravy by [[deglazing (cooking)|deglazing]] them&mdash;dissolving them in liquid.<ref>{{cite book|title=Cooking - A Basic Repertoire|chapter=Pots and Pans|author=Tony Polombo|pages=20|publisher=iUniverse|year=2006|isbn=9780595378661}}</ref> ====Ceramic==== Not all non-stick pans use Teflon; other non-stick coatings have become available. For example, a mixture of [[titanium]] and [[ceramic]] can be [[sandblasting|sandblasted]] onto the pan surface, and then [[pottery firing|fired]] at {{convert|2000|C|F}} to produce a non-stick ceramic coating.<ref>{{cite encyclopaedia|encyclopedia=A to Z of Inventions and Inventors: M to P|article=Non-stick pan|author=Pennie Stoyles and Peter Pentland|pages=[https://archive.org/details/atozofinventions0006stoy/page/17 17]|publisher=Black Rabbit Books|year=2007|isbn=9781583407899|url=https://archive.org/details/atozofinventions0006stoy/page/17}}</ref> Ceramic nonstick pans use a finish of silica (silicon dioxide) to prevent sticking. It is applied using a [[sol-gel process]] without the use of [[PFAS]].<ref>{{Cite web |title=You Can't Always Trust Claims on 'Non-Toxic' Cookware |url=https://www.consumerreports.org/toxic-chemicals-substances/you-cant-always-trust-claims-on-non-toxic-cookware-a4849321487/ |access-date=2022-11-11 |website=Consumer Reports |date=26 October 2022 |language=en-US}}</ref> The coating layer of Ceramic nonstick pans starts to break down at about 370 °C (700 °F).<ref>{{Cite web |last=trk |date=2020-07-28 |title=Is Nonstick Cookware Safe? |url=https://therationalkitchen.com/is-nonstick-cookware-safe/ |access-date=2023-07-20 |website=the rational kitchen |language=en-US}}</ref> The coating layer of PTFE cookware starts to break down when heated to 260&nbsp;°C. With the [[EPA]] imposing stricter limits on the use of PFAS,<ref>{{Cite web |date=2022-06-15 |title=EPA imposes stricter limits on four types of toxic 'forever chemicals' |url=https://www.theguardian.com/environment/2022/jun/15/epa-limits-toxic-forever-chemicals |access-date=2022-11-11 |website=the Guardian |language=en}}</ref> some companies are voluntarily replacing their PTFE cookware with ceramic options.<ref>{{Cite magazine |last=Ray |first=Joe |title=Teflon Nonstick Pans Are Bad. Consider These Alternatives |language=en-US |magazine=Wired |url=https://www.wired.com/story/ceramic-carbon-steel-nonstick/ |access-date=2022-11-11 |issn=1059-1028}}</ref> ===Superhydrophobic=== A [[superhydrophobic coating]] is a thin surface layer that repels water. It is made from superhydrophobic ([[ultrahydrophobicity]]) materials. Droplets hitting this kind of coating can fully rebound.<ref name="Richard2002">Richard, Denis, Christophe Clanet, and David Quéré. "Surface phenomena: Contact time of a bouncing drop." Nature 417.6891 (2002): 811-811</ref><ref name="Liu 2014">Yahua Liu, Lisa Moevius, Xinpeng Xu, Tiezheng Qian, Julia M Yeomans, Zuankai Wang. "Pancake bouncing on superhydrophobic surfaces." Nature Physics, 10, 515-519 (2014)</ref> Generally speaking, superhydrophobic coatings are made from composite materials where one component provides the roughness and the other provides low surface energy.<ref>{{Cite journal | doi = 10.1088/0034-4885/78/8/086501| pmid = 26181655| title = Superhydrophobic materials and coatings: a review| journal = Reports on Progress in Physics| volume = 78| issue = 8| pages = 086501| year = 2015| last1 = Simpson | first1 = John T. | last2 = Hunter | first2 = Scott R. | last3 = Aytug | first3 = Tolga | bibcode = 2015RPPh...78h6501S| s2cid = 206022154}}</ref> [[File:Super-hydrophobic coating.jpg|thumb|This image shows highly absorbent filter paper coated with a super-hydrophobic paint developed at [[University College London]]. This repels water (which has been dyed orange for greater contrast)]] ===Liquid-impregnated surface=== A [[liquid-impregnated surface]] consists of two distinct layers. The first is a highly [[Surface finish|textured]] or porous substrate with features spaced sufficiently close to stably contain the second layer which is an impregnating liquid that fills in the spaces between the features.<ref name="Patent A1">{{cite web|title=US Patent # US 20130032316 A1|url=https://patents.google.com/patent/US20130032316|work=US Patent|publisher=USPTO|access-date=18 October 2013}}</ref> The liquid must have a surface energy well-matched to the substrate in order to form a stable film.<ref>{{Cite journal|last1=Aizenberg|first1=Joanna|last2=Grinthal|first2=Alison|last3=Hatton|first3=Benjamin D.|last4=Smythe|first4=Elizabeth J.|last5=Tang|first5=Sindy K. Y.|last6=Kang|first6=Sung Hoon|last7=Wong|first7=Tak-Sing|date=September 2011|title=Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity|journal=Nature|volume=477|issue=7365|pages=443–447|doi=10.1038/nature10447|pmid=21938066|bibcode=2011Natur.477..443W|s2cid=4300247|issn=1476-4687|url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:27417441}}</ref> These surfaces bioimitate the carnivorous [[Heliamphora|Venezuelan pitcher plant]], which uses microscale hairs to create a water slide that causes ants to slip to their death. Slippery surfaces are finding applications in commercial products, anti-fouling surfaces, [[Deicing|anti-icing]] and [[biofilm]]-resistant medical devices. ==See also== *[[Cooking spray]] *[[Aluminium magnesium boride]] *[[Per- and polyfluoroalkyl substances#"Forever chemicals" moniker|Forever chemicals]] ==References== {{Reflist}} ==External links== * [http://home.howstuffworks.com/nonstick-cookware.htm How non-stick pan works] *[http://news.bbc.co.uk/1/hi/technology/3178136.stm "Science plans 'non-stick' submarine", ''bbc.co.uk'', 10 October, 2003] *{{cite web | url=http://news.bbc.co.uk/2/hi/science/nature/6993719.stm | title='Virtually non-stick' gum created | author=Rebecca Morelle | author-link=Rebecca Morelle | author2=Liz Seward | author2-link=Liz Seward| website=BBC News | date=13 September 2007}} *[http://home.howstuffworks.com/nonstick-cookware.htm How non-stick surface works- Illustration], from [[How Stuff Works]]. * [https://holscot.com/glossary/ptfe/ PTFE Properties] * [https://macclite.com/blogs/health-life-macclite/mastering-cookware-a-comprehensive-guide-to-materials-performance-maintenance-health-and-smart-buying-decisions A Guide to Materials, Performance, Maintenance, Health, & Smart Buying Decisions] [[Category:Materials science]] [[Category:Surface science]] [[Category:Cookware and bakeware]]'