Cookware and bakeware is food preparation equipment, such as cooking pots, pans, baking sheets etc. used in kitchens . Cookware is used on a stove or range cooktop , while bakeware is used in an oven . Some utensils are considered both cookware and bakeware.
94-461: Polytetrafluoroethylene ( PTFE ) is a synthetic fluoropolymer of tetrafluoroethylene , and has numerous applications because it is chemically inert . The commonly known brand name of PTFE-based composition is Teflon by Chemours , a spin-off from DuPont , which originally discovered the compound in 1938. Polytetrafluoroethylene is a fluorocarbon solid, as it is a high- molecular-weight polymer consisting wholly of carbon and fluorine . PTFE
188-611: A spit employed for roasting. By the 17th century, it was common for a Western kitchen to contain a number of skillets, baking pans, a kettle and several pots, along with a variety of pot hooks and trivets. Brass or copper vessels were common in Asia and Europe, whilst iron pots were common in the American colonies . Improvements in metallurgy during the 19th and 20th centuries allowed for pots and pans from metals such as steel, stainless steel and aluminium to be economically produced. At
282-432: A .35–45-mm-thick lining. Decorative copper cookware, i.e., a pot or pan less than 1 mm thick and therefore unsuited to cooking, will often be electroplate lined with tin. Should a wiped tin lining be damaged or wear out the cookware can be re-tinned, usually for much less cost than the purchase price of the pan. Tin presents a smooth crystalline structure and is therefore relatively non-stick in cooking applications. As
376-404: A basket from large leaves to boil water, according to historian and novelist Louis L'Amour . As long as the flames did not reach above the level of water in the basket, the leaves would not burn through. The development of pottery allowed for the creation of fireproof cooking vessels in a variety of shapes and sizes. Coating the earthenware with some type of plant gum, and later glazes, converted
470-513: A density of about 2200 kg/m and a melting point of 600 K (327 °C; 620 °F). It maintains high strength, toughness and self-lubrication at low temperatures down to 5 K (−268.2 °C; −450.7 °F), and good flexibility at temperatures above 194 K (−79.15 °C; −110.5 °F). PTFE gains its properties from the aggregate effect of carbon-fluorine bonds , as do all fluorocarbons. The only chemicals known to affect these carbon-fluorine bonds are highly reactive metals like
564-430: A foil layer of copper on the exterior to provide the "look" of a copper pot at a lower price. Enameled cast iron cooking vessels are made of cast iron covered with a porcelain surface. This creates a piece that has the heat distribution and retention properties of cast iron combined with a non-reactive, low-stick surface. The enamel over steel technique creates a piece that has the heat distribution of carbon steel and
658-402: A lifetime or more) and are inert and non-reactive. Heat is also conducted evenly in this material. They can be used for both cooking in a fire pit surrounded with coals and for baking in the oven. Glazed ceramics, such as porcelain , provide a nonstick cooking surface. Historically some glazes used on ceramic articles contained levels of lead , which can possess health risks; although this
752-589: A material to coat valves and seals in the pipes holding highly reactive uranium hexafluoride at the vast K-25 uranium enrichment plant in Oak Ridge, Tennessee . In 1954, Colette Grégoire urged her husband, the French engineer Marc Grégoire, to try the material he had been using on fishing tackle on her cooking pans. He subsequently created the first PTFE-coated, non-stick pans under the brand name Tefal (combining "Tef" from "Teflon" and "al" from aluminium). In
846-641: A minimal loss of performance over the lifetime of the gasket. PTFE is an ultraviolet (UV) transparent polymer. However, when exposed to an excimer laser beam it severely degrades due to heterogeneous photothermal effect . Processing PTFE can be difficult and expensive because its high melting temperature, 327 °C (621 °F), is above its decomposition temperature. Even when molten, PTFE does not flow due to its exceedingly high melt-viscosity. The viscosity and melting point can be decreased by inclusion of small amount of comonomers such as perfluoro (propylvinyl ether) and hexafluoropropylene (HFP). These cause
940-459: A non-reactive, low-stick surface. Such pots are much lighter than most other pots of similar size, are cheaper to make than stainless steel pots, and do not have the rust and reactivity issues of cast iron or carbon steel. Enamel over steel is ideal for large stockpots and for other large pans used mostly for water-based cooking. Because of its light weight and easy cleanup, enamel over steel is also popular for cookware used while camping. Seasoning
1034-406: A non-stick pan cannot be used where a pan sauce is desired. Non-stick coatings tend to degrade over time and are susceptible to damage. Using metal implements, harsh scouring pads, or chemical abrasives can damage or destroy cooking surface. Non-stick pans must not be overheated. The coating is stable at normal cooking temperatures, even at the smoke point of most oils. However, if a non-stick pan
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#17327931472411128-522: A pot may be made out of a more reactive metal, and then tinned or clad with another. While metal pots take heat very well, they usually react poorly to rapid cooling, such as being plunged into water while hot, this will usually warp the piece over time. Aluminium is a lightweight metal with very good thermal conductivity. It is resistant to many forms of corrosion. Aluminium is commonly available in sheet, cast, or anodized forms, and may be physically combined with other metals (see below). Sheet aluminium
1222-470: A relatively low magnetic permeability , making it incompatible with induction cooktops . Recent developments have allowed the production of ferromagnetic 18/10 alloys with a higher permeability. In so-called "tri-ply" cookware, the central aluminum layer is paramagnetic, and the interior 18/10 layer may also, but the exterior layer at the base must be ferromagnetic to be compatible with induction cooktops. Stainless steel does not require seasoning to protect
1316-500: A relatively soft metal abrasive cleansers or cleaning techniques can accelerate wear of tin linings. Wood, silicone or plastic implements are to preferred over harder stainless steel types. For a period following the Second World War, copper cookware was electroplated with a nickel lining. Nickel is harder and more thermally efficient than tin, with a higher melting point. Despite its hardness, it wore out as fast as tin, as
1410-591: A risk factor for Alzheimer's disease . The Alzheimer's Association states that "studies have failed to confirm any role for aluminum in causing Alzheimer's." The link remains controversial. Copper provides the highest thermal conductivity among non- noble metals and is therefore fast heating with unparalleled heat distribution (see: Copper in heat exchangers ). Pots and pans are cold-formed from copper sheets of various thicknesses, with those in excess of 2.5 mm considered commercial (or extra-fort ) grade. Between 1 mm and 2.5 mm wall thickness
1504-577: A single mass. The most common use of PTFE, consuming about 50% of production, is for the insulation of wiring in aerospace and computer applications (e.g. hookup wire, coaxial cables). This application exploits the fact that PTFE has excellent dielectric properties, specifically low group velocity dispersion , especially at high radio frequencies , making it suitable for use as an excellent insulator in connector assemblies and cables , and in printed circuit boards used at microwave frequencies. Combined with its high melting temperature, this makes PTFE
1598-399: A surfactant is the primary means of keeping PTFE in an aqueous medium. Surfactants in the past have included toxic perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). More recently, Perfluoro 3,6 dioxaoctanoic acid (PFO2OA) and FRD-903 (GenX) are being used as alternative surfactants. PTFE is a thermoplastic polymer , which is a white solid at room temperature, with
1692-405: A weight differential in his test cylinder, brought it to the attention of Roy Plunkett. The chemists in the lab sawed the bottle apart and found the bottle's interior coated with a waxy white material that was oddly slippery. Analysis showed that it was polymerized perfluoroethylene, with the iron from the inside of the container having acted as a catalyst at high pressure. Kinetic Chemicals patented
1786-433: Is hydrophobic : neither water nor water-containing substances wet PTFE, as fluorocarbons exhibit only small London dispersion forces due to the low electric polarizability of fluorine. PTFE has one of the lowest coefficients of friction of any solid. Polytetrafluoroethylene is used as a non-stick coating for pans and other cookware. It is non-reactive, partly because of the strength of carbon–fluorine bonds , so it
1880-467: Is polytetrafluoroethylene under the brand name "Teflon," trademarked by the DuPont Company. In 1938, polytetrafluoroethylene ( DuPont brand name Teflon) was discovered by accident by a recently hired DuPont Ph.D., Roy J. Plunkett . While working with tetrafluoroethylene gas to develop refrigerants, he noticed that a previously pressurized cylinder had no pressure remaining. In dissecting
1974-534: Is a brand of expanded PTFE (ePTFE), a material incorporating a fluoropolymer membrane with micropores. The roof of the Hubert H. Humphrey Metrodome in Minneapolis , US, was one of the largest applications of PTFE coatings. 20 acres (81,000 m) of the material was used in the creation of the white double-layered PTFE-coated fiberglass dome. Because of its extreme non-reactivity and high temperature rating, PTFE
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#17327931472412068-443: Is a great variety of cookware and bakeware in shape, material, and inside surface. Some materials conduct heat well ; some retain heat well. Some surfaces are non-stick ; some require seasoning . Some pots and their lids have handles or knobs made of low thermal conductance materials such as bakelite , plastic or wood , which make them easy to pick up without oven gloves . A good cooking pot design has an "overcook edge" which
2162-410: Is a somewhat brittle, porous material that rusts easily. As a result, it should not be dropped or heated unevenly and it typically requires seasoning before use. Seasoning creates a thin layer of oxidized fat over the iron that coats and protects the surface from corrosion, and prevents sticking. Enameled cast-iron cookware was developed in the 1920s. In 1934, the French company Cousances designed
2256-514: Is also possible to extrapolate likely developments based on methods used by latter peoples. Among the first of the techniques believed to be used by Stone Age civilizations were improvements to basic roasting . In addition to exposing food to direct heat from either an open fire or hot embers, it is possible to cover the food with clay or large leaves before roasting to preserve moisture in the cooked result. Examples of similar techniques are still in use in many modern cuisines. Of greater difficulty
2350-581: Is considered a minor exposure pathway to PFOA. As a result of the lawsuits concerning the PFOA class-action lawsuit , DuPont began to use GenX, a similarly fluorinated compound, as a replacement for perfluorooctanoic acid in the manufacture of fluoropolymers , such as Teflon-brand PTFE. However, the EPA has classified GenX as more toxic than PFOA and it has proven to be a “regrettable substitute”; its effects may be equally harmful or even more detrimental than those of
2444-444: Is considered utility ( fort ) grade, with thicknesses below 1.5 mm often requiring tube beading or edge rolling for reinforcement. Less than 1mm wall thickness is generally considered decorative, with exception made for the case of .75–1 mm planished copper, which is hardened by hammering and therefore expresses performance and strength characteristic of thicker material. Copper thickness of less than .25 mm is, in
2538-589: Is frequently incorporated into cookware constructed of primarily dissimilar metal, such as stainless steel, often as an enclosed diffusion layer (see coated and composite cookware below). Cast-iron cookware is slow to heat, but once at temperature provides even heating. Cast iron can also withstand very high temperatures, making cast iron pans ideal for searing . Being a reactive material, cast iron can have chemical reactions with high acid foods such as wine or tomatoes . In addition, some foods (such as spinach ) cooked on bare cast iron will turn black. Cast iron
2632-717: Is heated while empty its temperature may quickly exceed 260 °C (500 °F), above which the non-stick coating may begin to deteriorate, changing color and losing its non-stick properties. Non- metallic cookware can be used in both conventional and microwave ovens . Non-metallic cookware typically can not be used on the stovetop, with the exception of glass-ceramic cookware. Rigid non metallic cookware tends to shatter on sudden cooling or uneven heating, although low expansion materials such as borosilicate glass and glass-ceramics have significant immunity. Pottery has been used to make cookware from before dated history. Pots and pans made with this material are durable (some could last
2726-905: Is no longer being made in the United States. PTFE was added to the Living Building Challenge (LBC) Red List in 2016. The Red List bans substances prevalent in the building industry that pose serious risks to human health and the environment from construction that seeks to meet the criteria of the Living Building Challenge (LBC). Sodium trifluoroacetate and the similar compound sodium chlorodifluoroacetate can both be generated when PTFE undergoes thermolysis , as well as producing longer chain polyfluoro- and/or polychlorofluoro- (C3-C14) carboxylic acids which may be equally persistent. These products can accumulate in evaporative wetlands and have been found in
2820-420: Is not a concern with the vast majority of modern ware. Some pottery can be placed on fire directly. Borosilicate glass is safe at oven temperatures. The clear glass also allows for the food to be seen during the cooking process. However, it cannot be used on a stovetop, as it cannot cope with stovetop temperatures. Glass ceramic is used to make products such as Corningware and Pyroflam , which have many of
2914-563: Is notable for its extremely low coefficient of friction, its hydrophobia (which serves to inhibit rust), and for the dry film it forms after application, which allows it to resist collecting particles that might otherwise form an abrasive paste. Brands include GT85, Tri-Flow and WD-40 Specialist. PTFE is best known for its use in coating non-stick frying pans and other cookware, as it is hydrophobic and possesses fairly high heat resistance. The sole plates of some clothes irons are coated with PTFE. Other niche applications include: While PTFE
Polytetrafluoroethylene - Misplaced Pages Continue
3008-403: Is often used as the liner in hose assemblies, expansion joints , and in industrial pipe lines, particularly in applications using acids, alkalis, or other chemicals. Its frictionless qualities allow improved flow of highly viscous liquids and for uses in applications such as brake hoses. PTFE architectural membranes are created by coating a woven glass-fibre base cloth with PTFE, forming one of
3102-667: Is often used in containers and pipework for reactive and corrosive chemicals. Where used as a lubricant , PTFE reduces friction, wear, and energy consumption of machinery. It is used as a graft material in surgery and as a coating on catheters . PTFE and chemicals used in its production are some of the best-known and widely applied PFAS , which are persistent organic pollutants . PTFE occupies more than half of all fluoropolymer production, followed by polyvinylidene fluoride (PVdF) . For decades, DuPont used perfluorooctanoic acid (PFOA, or C8) during production of PTFE, later discontinuing its use due to legal actions over ecotoxicological and
3196-954: Is recommended and safe, for instance in the preparation of meringue , where copper ions prompt proteins to denature (unfold) and enable stronger protein bonds across the sulfur contained in egg whites. Unlined copper is also used in the making of preserves, jams and jellies. Copper does not store ("bank") heat, and so thermal flows reverse almost immediately upon removal from heat. This allows precise control of consistency and texture while cooking sugar and pectin-thickened preparations. Alone, fruit acid would be sufficient to cause leaching of copper byproducts, but naturally occurring fruit sugars and added preserving sugars buffer copper reactivity. Unlined pans have thereby been used safely in such applications for centuries. Lining copper pots and pans prevents copper from contact with acidic foods. The most popular lining types are tin , stainless steel , nickel and silver . The use of tin dates back many centuries and
3290-422: Is spun or stamped into form. Due to the softness of the metal, it may be alloyed with magnesium, copper, or bronze to increase its strength. Sheet aluminium is commonly used for baking sheets, pie plates, and cake or muffin pans. Deep or shallow pots may be formed from sheet aluminium. Cast aluminium can produce a thicker product than sheet aluminium, and is appropriate for irregular shapes and thicknesses. Due to
3384-437: Is stable at lower temperatures, it begins to deteriorate at temperatures of about 260 °C (500 °F), it decomposes above 350 °C (662 °F), and pyrolysis occurs at temperatures above 400 °C (752 °F). The main decomposition products are fluorocarbon gases and a sublimate , including tetrafluoroethylene (TFE) and difluorocarbene radicals (RCF2). An animal study conducted in 1955 concluded that it
3478-419: Is still very often employed by professional chefs to avoid sticking. Seasoning of other cookware surfaces is generally discouraged. Non-stick enamels often crack under heat stress, and non-stick polymers (such as Teflon) degrade at high heat so neither type of surface should be seasoned. Steel or aluminum cooking pans can be coated with a substance such as polytetrafluoroethylene (PTFE, often referred to with
3572-617: Is the original lining for copper cookware. Although the patent for canning in sheet tin was secured in 1810 in England, legendary French chef Auguste Escoffier experimented with a solution for provisioning the French army while in the field by adapting the tin lining techniques used for his cookware to more robust steel containers (then only lately introduced for canning) which protected the cans from corrosion and soldiers from lead solder and botulism poisoning. Tin linings sufficiently robust for cooking are wiped onto copper by hand, producing
3666-758: Is the process of treating the surface of a cooking vessel with a dry, hard, smooth, hydrophobic coating formed from polymerized fat or oil. When seasoned surfaces are used for cookery in conjunction with oil or fat a stick-resistant effect is produced. Some form of post-manufacturing treatment or end-user seasoning is mandatory on cast-iron cookware , which rusts rapidly when heated in the presence of available oxygen, notably from water, even small quantities such as drippings from dry meat. Food tends to stick to unseasoned iron and carbon steel cookware, both of which are seasoned for this reason as well. Other cookware surfaces such as stainless steel or cast aluminium do not require as much protection from corrosion but seasoning
3760-424: Is traditionally used for crêpe and fry pans, as well as woks. Cladding is a technique for fabricating pans with a layer of efficient heat conducting material, such as copper or aluminum, covered on the cooking surface by a non-reactive material such as stainless steel, and often covered on the exterior aspect of the pan ("dual-clad") as well. Some pans feature a copper or aluminum interface layer that extends over
3854-439: Is typically initiated with persulfate , which homolyzes to generate sulfate radicals: The resulting polymer is terminated with sulfate ester groups, which can be hydrolyzed to give OH end-groups . Granular PTFE is produced via suspension polymerization, where PTFE is suspended in an aqueous medium primarily via agitation and sometimes with the use of a surfactant. PTFE is also synthesized via emulsion polymerization, where
Polytetrafluoroethylene - Misplaced Pages Continue
3948-565: Is unlikely that these products would be generated in amounts significant to health at temperatures below 250 °C (482 °F). Above those temperatures the degradation by-products can be lethal to birds , and can cause flu-like symptoms in humans ( polymer fume fever ), although in humans those symptoms disappear within a day or two of being moved to fresh air. Most cases of polymer fume fever in humans occur due to smoking PTFE-contaminated tobacco, although cases have occurred in people who have welded near PTFE components. PTFE-coated cookware
4042-434: Is unlikely to reach dangerous temperatures with normal use, as meat is usually fried between 204 and 232 °C (399 and 450 °F), and most cooking oils (except refined safflower and avocado oils) start to smoke before a temperature of 260 °C (500 °F) is reached. A 1973 study by DuPont's Haskell Laboratory found that a 4-hour exposure to the fumes emitted by PTFE cookware heated to 280 °C (536 °F)
4136-496: Is usually measured against polished steel. PTFE's coefficient of friction is 0.05 to 0.10, which is the third-lowest of any known solid material ( aluminium magnesium boride (BAM) being the lowest, with a coefficient of friction of 0.02; diamond-like carbon being second-lowest at 0.05). PTFE's resistance to van der Waals forces means that it is the only known surface to which a gecko cannot stick. In addition, PTFE can be used to prevent insects from climbing up surfaces painted with
4230-582: Is what the lid lies on. The lid has a dripping edge that prevents condensation fluid from dripping off when handling the lid (taking it off and holding it 45°) or putting it down. The history of cooking vessels before the development of pottery is minimal due to the limited archaeological evidence. The earliest pottery vessels, dating from 19,600 ± 400 BP , were discovered in Xianrendong Cave , Jiangxi , China. The pottery may have been used as cookware, manufactured by hunter-gatherers . It
4324-473: The alkali metals , at higher temperatures such metals as aluminium and magnesium, and fluorinating agents such as xenon difluoride and cobalt(III) fluoride . At temperatures above 650–700 °C (1,200–1,290 °F) PTFE undergoes depolymerization. However, it begins to decompose at about 260 °C (500 °F) through 350 °C (662 °F), and pyrolysis occurs at temperatures above 400 °C (752 °F). The coefficient of friction of plastics
4418-460: The electrostatic analogues of permanent magnets . PTFE film is also widely used in the production of carbon fiber composites as well as fiberglass composites, notably in the aerospace industry. PTFE film is used as a barrier between the carbon or fiberglass part being built and, in breather and bagging materials, is used to incapsulate the bondment when debulking (vacuum removal of air from between layers of laid-up plies of material) and when curing
4512-400: The genericized trademark Teflon) in order to minimize food sticking to the pan surface. There are advantages and disadvantages to such a coating. Coated pans are easier to clean than most non-coated pans, and require little or no additional oil or fat to prevent sticking, a property that helps to produce lower fat food. On the other hand, some sticking is required to cause sucs to form, so
4606-432: The health effects of exposure to PFOA . Dupont's spin-off Chemours today manufactures PTFE using an alternative chemical it calls GenX , another PFAS. Although GenX was designed to be less persistent in the environment compared to PFOA, it has proven to be a “regrettable substitute.” Its effects may be equally harmful or even more detrimental than those of the chemical it was meant to replace. Polytetrafluoroethylene (PTFE)
4700-448: The stovetop , and are only intended for the oven. The development of bronze and iron metalworking skills allowed for cookware made from metal to be manufactured, although adoption of the new cookware was slow due to the much higher cost. After the development of metal cookware there was little new development in cookware, with the standard Medieval kitchen utilizing a cauldron and a shallow earthenware pan for most cooking tasks, with
4794-495: The 1968 Miss America protest , protestors symbolically threw a number of feminine products into a "Freedom Trash Can", which included pots and pans. Metal pots are made from a narrow range of metals because pots and pans need to conduct heat well, but also need to be chemically unreactive so that they do not alter the flavor of the food. Most materials that are conductive enough to heat evenly are too reactive to use in food preparation. In some cases (copper pots, for example),
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#17327931472414888-428: The 1990s, PTFE was not known to crosslink like an elastomer , due to its chemical inertness. Therefore, it has no "memory" and is subject to creep . Because of the propensity to creep, the long-term performance of such seals is worse than for elastomers that exhibit zero, or near-zero, levels of creep. In critical applications, Belleville washers are often used to apply continuous force to PTFE gaskets, thereby ensuring
4982-535: The 1990s, it was found that PTFE could be radiation cross-linked above its melting point in an oxygen-free environment. Electron beam processing is one example of radiation processing. Cross-linked PTFE has improved high-temperature mechanical properties and radiation stability. That was significant because, for many years, irradiation at ambient conditions has been used to break down PTFE for recycling. This radiation-induced chain scission allows it to be more easily reground and reused. Corona discharge treatment of
5076-581: The Manhattan Project. Fluoropolymers share the properties of fluorocarbons in that they are not as susceptible to the van der Waals force as hydrocarbons . This contributes to their non-stick and friction reducing properties. Also, they are stable due to the stability multiple carbon–fluorine bonds add to a chemical compound . Fluoropolymers may be mechanically characterized as thermosets or thermoplastics . Fluoropolymers can be homopolymers or Copolymer. Non-stick pans There
5170-408: The United States, Marion A. Trozzolo , who had been using the substance on scientific utensils, marketed the first US-made PTFE-coated pan, "The Happy Pan", in 1961. Non-stick cookware has since become a common household product, now offered by hundreds of manufacturers across the world. The brand name Zepel was used for promoting its stain-resistance and water-resistance when applied to fabrics. In
5264-643: The area beginning in 1976 with the production of Nafion, and that PFAS including GenX had been released as a byproduct of the production of Vinyl Ethers since 1980, exposing the Cape Fear Basin for decades. A small nonprofit called Cape Fear River Watch sued NC DEQ for not taking swifter and stronger action, and sued the polluter, Chemours, for violations of the Clean Water Act and the Toxic Substances Control Act. The result
5358-424: The best properties of both glass and ceramic cookware. While Pyrex can shatter if taken between extremes of temperature too rapidly, glass-ceramics can be taken directly from deep freeze to the stove top. Their very low coefficient of thermal expansion makes them less prone to thermal shock . A natural stone can be used to diffuse heat for indirect grilling or baking, as in a baking stone or pizza stone , or
5452-459: The blood of people who work in or live near factories where the chemical is used, and in people regularly exposed to PFOA-containing products such as some ski waxes and stain-resistant fabric coatings, but non-stick cookware was not found to be a major source of exposure, as the PFOA is burned off during the manufacturing process and not present in the finished product. Non-stick coated cookware has not been manufactured using PFOA since 2013, and PFOA
5546-411: The case of cookware, referred to as foil and must be formed to a more structurally rigid metal to produce a serviceable vessel. Such applications of copper are purely aesthetic and do not materially contribute to cookware performance. Copper is reactive with acidic foods which can result in corrosion, the byproducts of which can foment copper toxicity . In certain circumstances, however, unlined copper
5640-645: The chemical it was meant to replace. The chemicals are manufactured by Chemours , a corporate spin-off of DuPont, in Fayetteville, North Carolina . Fayetteville Works was the site where DuPont began manufacture of PFOA after the lawsuit in Parkersburg WV halted their production there. When EPA asked companies to voluntarily phase out PFOA production, it was replaced by GenX in Fayetteville Works. In June of 2017, The Wilmington Star-News broke
5734-424: The composite, usually in an autoclave. The PTFE, used here as a film, prevents the non-production materials from sticking to the part being built, which is sticky due to the carbon-graphite or fiberglass plies being pre-pregnated with bismaleimide resin. Non-production materials such as Teflon, Airweave Breather, and the bag itself would be considered F.O.D. (foreign object debris/damage) if left in layup. Gore-Tex
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#17327931472415828-469: The copper with which it is bonded. Among the advantages of stainless steel are its durability and corrosion resistance, and although relatively sticky and subject to food residue adhesions, stainless steel is tolerant of most abrasive cleaning techniques and metal implements. Stainless steel forms a pan's structural element when bonded to copper and is irreparable in the event of wear or damage. Using modern metal bonding techniques, such as cladding , copper
5922-411: The cylinder, he found a mass of white solid in a quantity similar to that of the tetrafluoroethylene gas. It was determined that this material was a new-to-the-world polymer . Tests showed the substance was resistant to corrosion from most acids, bases and solvents and had better high temperature stability than any other plastic. By early 1941, a crash program was making substantial quantities of PTFE for
6016-460: The enameled cast iron Doufeu to reduce excessive evaporation and scorching in cast iron Dutch ovens. Modeled on old braising pans in which glowing charcoal was heaped on the lids (to mimic two-fire ovens), the Doufeu has a deep recess in its lid which instead is filled with ice cubes. This keeps the lid at a lower temperature than the pot bottom. Further, little notches on the inside of the lid allow
6110-607: The end of the production and phase out of PFOA and PFOS in the US. The general population has been exposed to PFOA through massive dumping of C8 waste into the ocean and near the Ohio River Valley. PFOA has been detected in industrial waste, stain-resistant carpets, carpet cleaning liquids, house dust , microwave popcorn bags , water, food and PTFE cookware. As a result of a class-action lawsuit and community settlement with DuPont , three epidemiologists conducted studies on
6204-615: The end with clay provided a usable container in Asia, while the inhabitants of the Tehuacan Valley began carving large stone bowls that were permanently set into a hearth as early as 7,000 BC. According to Frank Hamilton Cushing, Native American cooking baskets used by the Zuni (Zuñi) developed from mesh casings woven to stabilize gourd water vessels. He reported witnessing cooking basket use by Havasupai in 1881. Roasting baskets covered with clay would be filled with wood coals and
6298-411: The entire pan rather than just a heat-distributing disk on the base. Generally, the thicker the interface layer, especially in the base of the pan, the more improved the heat distribution. Claims of thermal efficiency improvements are, however, controversial, owing in particular to the limiting and heat-banking effect of stainless steel on thermal flows. Aluminum is typically clad on both the inside and
6392-452: The exterior pan surfaces, providing both a stainless cooking surface and a stainless surface to contact the cooktop. Copper of various thicknesses is often clad on its interior surface only, leaving the more attractive copper exposed on the outside of the pan (see Copper above). Some cookware use a dual-clad process, with a thin stainless layer on the cooking surface, a thick core of aluminum to provide structure and improved heat diffusion, and
6486-418: The general US population in the low and sub- parts per billion range, and levels are higher in chemical plant employees and surrounding subpopulations. PFOA and perfluorooctanesulfonic acid (PFOS) have been estimated to be in every American person's blood stream in the parts per billion range, though those concentrations have decreased by 70% for PFOA and 84% for PFOS between 1999 and 2014, which coincides with
6580-467: The isolation of nickel as an allergen. Silver is also applied to copper by means of electroplating, and provides an interior finish that is at once smooth, more durable than either tin or nickel, relatively non-stick and extremely thermally efficient. Copper and silver bond extremely well owing to their shared high electro-conductivity . Lining thickness varies widely by maker, but averages between 7 and 10 microns. The disadvantages of silver are expense and
6674-414: The material does not adequately spread the heat itself, stainless steel cookware is generally made as a cladding of stainless steel on both sides of an aluminum or copper core to conduct the heat across all sides, thereby reducing "hot spots", or with a disk of copper or aluminum on just the base to conduct the heat across the base, with possible "hot spots" at the sides. Typical 18/10 stainless steel also has
6768-512: The material of choice as a high-performance substitute for the weaker, higher dispersion and lower-melting-point polyethylene commonly used in low-cost applications. In industrial applications, owing to its low friction, PTFE is used for plain bearings , gears , slide plates , seals, gaskets, bushings, and more applications with sliding action of parts, where it outperforms acetal and nylon . Its extremely high bulk resistivity makes it an ideal material for fabricating long-life electrets ,
6862-410: The material. For example, PTFE is used to prevent ants from climbing out of formicaria . There are surface treatments for PTFE that alter the surface to allow adhesion to other materials. Because of its chemical and thermal properties, PTFE is often used as a gasket material within industries that require resistance to aggressive chemicals such as pharmaceuticals or chemical processing. However, until
6956-432: The microscopic pores caused by the casting process, cast aluminium has a lower thermal conductivity than sheet aluminium. It is also more expensive. Accordingly, cast aluminium cookware has become less common. It is used, for example, to make Dutch ovens lightweight and bundt pans heavy duty, and used in ladles and handles and woks to keep the sides at a lower temperature than the center. Anodized aluminium has had
7050-806: The moisture to collect and drop back into the food during the cooking. Although the Doufeu (literally, "gentlefire") can be used in an oven (without the ice, as a casserole pan), it is chiefly designed for stove top use. Enameled cast-iron cookware, unlike uncoated cast-iron, is minimally reactive thus can be used with acidic food. Stainless steel is an iron alloy containing a minimum of 11.5% chromium. Blends containing 18% chromium with either 8% nickel, called 18/8 , or with 10% nickel, called 18/10, are commonly used for kitchen cookware. Stainless steel's virtues are resistance to corrosion, non-reactivity with either alkaline or acidic foods, and resistance to scratching and denting. Stainless steel's drawbacks for cooking use include its relatively poor thermal conductivity. Since
7144-469: The naturally occurring layer of aluminium oxide thickened by an electrolytic process to create a surface that is hard and non-reactive. It is used for sauté pans, stockpots, roasters, and Dutch ovens. Uncoated and un-anodized aluminium can react with acidic foods to change the taste of the food. Sauces containing egg yolks, or vegetables such as asparagus or artichokes may cause oxidation of non-anodized aluminium. Aluminium exposure has been suggested as
7238-583: The new fluorinated plastic (analogous to the already known polyethylene ) in 1941, and registered the Teflon trademark in 1945. By 1948, DuPont, which founded Kinetic Chemicals in partnership with General Motors , was producing over 910,000 kilograms (2,000,000 lb) of Teflon-brand polytetrafluoroethylene per year in Parkersburg, West Virginia . An early use was in the Manhattan Project as
7332-420: The otherwise perfectly linear PTFE chain to become branched, reducing its crystallinity. Some PTFE parts are made by cold-moulding, a form of compression molding . Here, fine powdered PTFE is forced into a mould under high pressure (10–100 MPa). After a settling period, lasting from minutes to days, the mould is heated at 360 to 380 °C (680 to 716 °F), allowing the fine particles to fuse ( sinter ) into
7426-525: The pan is intentionally kept at a different temperature than the rest. Like cast iron, carbon steel must be seasoned before use, usually by rubbing a fat or oil on the cooking surface and heating the cookware on the stovetop or in the oven. With proper use and care, seasoning oils polymerize on carbon steel to form a low-tack surface, well-suited to browning, Maillard reactions and easy release of fried foods. Carbon steel will easily rust if not seasoned and should be stored seasoned to avoid rusting. Carbon steel
7520-402: The plating was 20 microns thick or less, as nickel tends to plate somewhat irregularly, and requires milling to produce an even cooking surface. Nickel is also stickier than tin or silver. Copper cookware with aged or damaged nickel linings can be retinned, or possibly replating with nickel, although this is no longer widely available. Nickel linings began to fall out of favor in the 1980s owing to
7614-499: The population of Parkersburg, WV surrounding the (former DuPont) Chemours Washington Works chemical plant that was exposed to PFOA at levels greater than in the general population. The studies concluded that there was an association between PFOA exposure and six health outcomes: kidney cancer , testicular cancer , ulcerative colitis , thyroid disease , hypercholesterolemia (high cholesterol), and gestational hypertension (pregnancy-induced high blood pressure). Overall, PTFE cookware
7708-409: The porous container into a waterproof vessel. The earthenware cookware could then be suspended over a fire through use of a tripod or other apparatus, or even be placed directly into a low fire or coal bed as in the case of the pipkin . Ceramics conduct heat poorly, however, so ceramic pots must cook over relatively low heats and over long periods of time. However, most ceramic pots will crack if used on
7802-457: The product to be roasted. When the thus-fired clay separated from the basket, it would become a usable clay roasting pan in itself. This indicates a steady progression from use of woven gourd casings to waterproof cooking baskets to pottery. Other than in many other cultures, Native Americans used and still use the heat source inside the cookware. Cooking baskets are filled with hot stones and roasting pans with wood coals. Native Americans would form
7896-425: The roots and seeds of wetland plant species, but has not been observed to have an adverse impact on plant health or germination success. Perfluorooctanoic acid (PFOA, or C8) has been used as a surfactant in the emulsion polymerization of PTFE, although several manufacturers have entirely discontinued its use. PFOA persists indefinitely in the environment. PFOA has been detected in the blood of many individuals of
7990-591: The story that GenX was found in the Cape Fear River – the drinking water supply for 500,000 people. The source of the pollution was determined to be the Fayetteville Works site, which had been run by DuPont since its founding in 1971 and then managed by DuPont spinoff, The Chemours Company, since 2015. The water utility confirmed they had no ability to filter these chemicals from the drinking water. The North Carolina Department of Environmental Quality (NC DEQ) records indicate that DuPont started release PFAS into
8084-782: The strongest and most durable materials used in tensile structures . Some notable structures featuring PTFE-tensioned membranes include The O2 Arena in London, Moses Mabhida Stadium in South Africa, Metropolitano Stadium in Spain and the Sydney Football Stadium Roof in Australia. PTFE is often found in musical instrument lubrication products, most commonly valve oil. PTFE is used in some aerosol lubricant sprays, including in micronized and polarized form. It
8178-465: The surface from rust, but may be seasoned to provide a non-stick surface. Carbon-steel cookware can be rolled or hammered into relatively thin sheets of dense material, which provides robust strength and improved heat distribution. Carbon steel accommodates high, dry heat for such operations as dry searing. Carbon steel does not conduct heat efficiently, but this may be an advantage for larger vessels, such as woks and paella pans, where one portion of
8272-483: The surface to increase the energy and improve adhesion has been reported. PTFE is produced by free-radical polymerization of tetrafluoroethylene . The net equation is Because tetrafluoroethylene can explosively decompose to tetrafluoromethane ( CF 4 {\textstyle {\ce {CF4}}} ) and carbon, a special apparatus is required for the polymerization to prevent hot spots that might initiate this dangerous side reaction. The process
8366-402: The tendency of sulfurous foods, especially brassicas , to discolor. Worn silver linings on copper cookware can be restored by stripping and re-electroplating. Copper cookware lined with a thin layer of stainless steel is available from most modern European manufacturers. Stainless steel is 25 times less thermally conductive than copper, and is sometimes critiqued for compromising the efficacy of
8460-470: The useful PTFE properties of low friction and nonreactivity, but are also more easily formable. For example, FEP is softer than PTFE and melts at 533 K (260 °C; 500 °F); it is also highly transparent and resistant to sunlight. Fluoropolymer A fluoropolymer is a fluorocarbon -based polymer with multiple carbon–fluorine bonds . It is characterized by a high resistance to solvents , acids , and bases . The best known fluoropolymer
8554-462: Was a Consent Order, signed February 25, 2019 by Cape Fear River Watch, NC DEQ, and Chemours. The order has required Chemours to stop wastewater discharge, air emissions, groundwater discharge, sampling and filtration options to well users, and required sampling that proved there were upwards of 300 distinct PFAS compounds being released from Fayetteville Works. The Teflon trade name is also used for other polymers with similar compositions: These retain
8648-539: Was accidentally discovered in 1938 by Roy J. Plunkett while he was working in Chemours Chambers Works plant in New Jersey for DuPont . A team of Dupont chemists attempted to make a new chlorofluorocarbon refrigerant, called tetrafluoroethylene . The gas in its pressure bottle stopped flowing before the bottle's weight had dropped to the point signaling "empty". John J. Beall (chemist), noticing
8742-432: Was finding a method to boil water. For people without access to natural heated water sources, such as hot springs, heated stones (" pot boilers ") could be placed in a water-filled vessel to raise its temperature (for example, a leaf-lined pit or the stomach from animals killed by hunters). In many locations the shells of turtles or large mollusks provided a source for waterproof cooking vessels. Bamboo tubes sealed at
8836-421: Was lethal for parakeets , although that was a higher temperature than the 260 °C (500 °F) required for fumes from pyrolyzed butter to be lethal to the birds. Perfluorooctanoic acid (PFOA), a chemical formerly used in the manufacture of PTFE products such as non-stick coated cookware, can be carcinogenic for people who are exposed to it (see Ecotoxicity ). Concerning levels of PFOA have been found in
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