How Nonstick Cookware Works
With busy schedules and long to-do lists, people are constantly looking for ways to save time. From drive-through to carry-out, restaurants offer more ways to get food fast. For people who prefer home cooking, cookbooks and Web sites are boasting meals that can be completed in less than 30 minutes and make-ahead options to reheat at dinnertime.
But for some chefs, it's less about the time it takes to make food and more about the time it takes to clean up. That's where nonstick cookware comes in. Nonstick cookware lets people fry, sauté, stew and bake with less mess and less fat. While the true merits of some nonstick technologies have been the subject of debate, this kitchen convenience offers an alternative to hours of scrubbing the remains of a grilled cheese sandwich or pancake batter from the inside of a pan.
Yet without a chance discovery, nonstick cookware might never have been invented in the first place. Following nonstick cookware from the first nonstick technology to recent advancements in the world of pots and pans, this article will cover everything from coating chemistry to the process used to bind a nonstick surface to a pan. You'll pick up a few tips on how to maintain and preserve the nonstick coating on your pans, and you'll get the scoop on whether nonstick cookware is as dangerous as some reports claim it is.
We'll start by exploring the accidental discovery of the world's first nonstick technology and how it led to the first piece of nonstick cookware in the United States.
Nonstick Cookware History
The discovery of the first nonstick technology started with research on another modern kitchen staple -- the refrigerator. Scientists at the Kinetic Chemicals plant, a subsidiary of DuPont, were searching for a less toxic chemical to use as a new refrigerant.
An Ohio-born scientist named Roy Plunkett was part of this research team. In 1938, he set up a mixture meant to produce tetrafluoroethylene gas and left it overnight. The next morning, he arrived to work to find a white, waxy substance in place of the gas he had expected. After analysis, the new substance was found to be polytetrafluoroethylene, or PTFE, and was quickly recognized as an exceptionally slippery substance. The chemical was patented in1941. DuPont trademarked the process and chemical as Teflon in 1945 [source: DuPont]. Plunkett was inducted into the National Inventors Hall of Fame for his invention of Teflon in 1985 [source: National Inventors Hall of Fame Foundation].
It was not until Marc Gregoire, a French engineer, found a way to bond PTFE to aluminum that the first nonstick cookware was created. Marc Gregoire and his wife, Colette, started selling their cookware in France. In 1956, they founded the Tefal Corporation [source: T-fal]. The U.S. Food and Drug Administration (FDA) approved PTFE for food processing equipment in 1960 [source: Blumenthal]. With this approval, Tefal, known as T-fal in the U.S., began selling its pans in the United States. Other manufacturers soon joined the market.
Today, lots of people describe their nonstick pots and pans as "Teflon," but using the term to describe anything with a nonstick coating is incorrect. Teflon is a brand name -- not all PTFE or other fluoropolymers used to produce nonstick cookware fall under the Teflon brand. Next, we'll take a closer look at PTFE and how it keeps what you're cooking from sticking to what you're cooking in.
Nonstick Science
In order to understand why polytetrafluoroethylene (PTFE) is a useful nonstick coating, we must take a closer look at its structure and properties. PTFE is a type of fluoropolymer. A polymer is a large molecule made up of smaller molecules of the same type. Fluoropolymers are polymers that include the fluorine atom, which is the key to many of the unique characteristics of PTFE. According to William Raiford, technology manager with DuPont Fluoroproducts, fluorine's electron structure is very stable -- it doesn't share its electrons with other atoms easily.
The chemical composition of PTFE is based on two carbon atoms and four fluorine atoms, which are repeated throughout the molecule's structure. "The molecular structure has an outer shell filled with fluorine atoms," says Raiford. "The fluorine atoms shield the carbon atoms from reacting."
Think about a high school dance. The fluorine atoms are the chaperones, and the carbon atoms are the femalestudents. Anything that might interact with the carbon is the male students. As chaperones, the fluorine atoms keep the boys from interacting with the girls -- in a frying pan, it keeps the food from sticking.
Along with their resistance to reacting with other chemicals, fluorine atoms also play a role in giving PTFE a lowcoefficient of friction. The coefficient of friction is a measurement of how easy it is for two substances to slide by each other -- the harder it is to slide, the higher the coefficient of friction. PTFE doesn't put up a lot of resistance when sliding by another substance, giving it a low coefficient of friction. The low coefficient of friction gives PTFE that signature slippery quality.
PTFE is not the only fluoropolymer used to make nonstick cookware. According to Raiford, other polymers of the same family have been developed with slightly refined structures to offer easier application, more strength or decorative looks to the nonstick surface.
In the next section, we will answer the question of how scientists are able to get PTFE -- something that's inherently nonsticky -- to stick to metal cookware.
PTFE and Cookware
Polytetrafluoroethylene (PTFE) has a unique slickness and inactivity with other chemicals that make it very useful in many applications -- it's a component in space suits, and it insulates high-voltage wires [source:DuPont]. Yet these characteristics also pose challenges when it comes to creating nonstick cookware. The nonstick coating must somehow stick to the surface of the pan.
There are many variations of the process to meld the nonstick coating onto the cookware's metal surface. Basically, they all start with the metal base, or substrate, which is created in the shape of the desired cookware. Most nonstick cookware is made of aluminum, but other metals, such as stainless steel, are also used.
The next part of the process deals with applying the nonstick coating to the pan substrate. According to DuPont technology manager William Raiford, there are two ways to overcome the nonstick problem -- mechanically and chemically.
Let's go back to the example of the dance. The chaperones keep the female students from interacting with the male students. To distract the chaperone, a male student might enlist a friend to create a disturbance on the other side of the room, causing all the chaperones to move in that direction. Another tactic might be to build some common ground among the chaperones and students by playing some music from the chaperones' era and getting everyone onto the dance floor together. Either way, the male dancers have a chance to dance with the females.
When making nonstick cookware, the manufacturing version of the male students' disturbance starts with roughening the surface of the substrate. This makes it easier for PTFE's fluorine molecules to stick to the surface. Some methods include roughing the surface with molten metal or chemicals [source: Wolke, Funderburg].
The common ground is a primer or base coat, which has a special formulation that allows it to adhere to both the metal substrate and several nonstick coating layers. The number of PTFE-based coatings, which are either sprayed or rolled onto the surface, depends on the type of pan [source: Cookware Manufacturers Association].
According to Raiford, this process can include heating between each layer, or the layers can be put on top of each other while they are still wet. The final step is sintering. "This is a high temperature bake usually at around 800 degrees Fahrenheit for about three to five minutes," Raiford says -- that's about 427 degrees Celsius. "This dries and cures the polymer and also helps to lock it to the metal."
This coating keeps everything from eggs to meatloaf from sticking to your pans -- but you can't scrub away at it like you can with some cookware. Next, we'll look at how to keep the nonstick finish on your pans pristine.
Caring for Nonstick Cookware
There are many brands and variations of nonstick cookware on the market today. The type of coatings, number of layers and thickness of the metal base are all part of the durability and longevity of the cookware. Heavier pans with more coatings are likely to cost moremoney [source: Cookware Manufacturers Association]. No matter which one you choose, the nonstick surface -- whether it's polytetrafluoroethylene (PTFE) or another fluoropolymer -- should be treated with care to help preserve the cookware's coating.
According to William Raiford of DuPont, most nonstick cookware coatings are expected to last from three to five years with normal use. How often the pan is used, the types of cooking done with the pan and the utensils used on the pan can all affect the lifespan of nonstick cookware.
While nonstick cookware shouldn't require too much hard scrubbing, normal cleaning can be done with warm, soapy water. Harsh abrasives and rough cleaning pads are not recommended.
To prevent scuffs and scratches on the nonstick surface on a pan, utensils made of wood, plastic or coated materials are the best choices. It's also a good idea to store the pan in a cabinet or area where it won't get scratched [source: DuPont].
One of the major selling points for nonstick cookware is that you can cook using less oil. This doesn't mean you can't use butter or oil in your cooking if you want to -- but lots of nonstick spray isn't recommended. It can eventually leave a residue that can hurt the nonstick surface's performance [source: T-fal].
Following some simple tips regarding use and cleaning can help to preserve your nonstick cookware. First, keeping the setting of your stove to low or medium is a good idea. Make sure your pan doesn't exceed temperatures of 450 to 500 degrees Fahrenheit (204 to 260 degrees Celsius). Heating an empty pan can make it reach very high temperatures more quickly. This recommendation has as much to do with safety as with maintaining your pans -- we'll look at how on the next page.
PTFE Safety Debate
While cookware using polytetrafluoroethylene (PTFE) has been around since the 1960s, its safety has become the subject of debate in recent years. The majority of the discussion has revolved around a substance called perfluorooctanoic acid, or PFOA. This acid is used in the production of many fluoropolymers, including PTFE.
In 2003, the Environmental Working Group petitioned the U.S. Consumer Product Safety Commission (CPSC) to put labels on PTFE-coated cookware to warn of potential safety concerns for both pet birds and humans [source:Houlihan and White]. The petition cited multiple cases of bird deaths due to fumes from PTFE nonstick coatings along with two specific incidents of polymer fume fever -- temporary flulike symptoms -- in humans. After review, the U.S. Consumer Product Safety Commission denied the Environmental Working Group's petition to require warning labels on PTFE-based nonstick cookware [source: Chemical Market Reporter].
In January 2005, the U.S. Environmental Protection Agency released a draft risk assessment on the health effects of PFOA. The EPA's Office of Pollution Prevention and Toxics formed a Science Advisory Board to review the draft's findings. According to the review letter, three-fourths of the panel found that PFOA fit the EPA's guidelines for a "likely to be carcinogenic" substance. [source: Cory-Slechta and Morgan]. But while the EPA is continuing to study PFOA's effects on humans and the environment and has a program to eliminate PFOA and related chemical emissions and products by 2015, its current stand is that there is no reason for consumers to stop using PTFE-based nonstick cookware [source: United States Environmental Protection Agency]. The final product is PTFE -- not PFOA.
Even though the CPSC and the EPA haven't determined a need for warning labels on nonstick cookware or pulled it from the market, it's still a good idea to follow a few guidelines in the kitchen. First, as DuPont -- maker Teflon, one of the best known nonstick cookware brands -- points out on its Web site, birds have delicate respiratory systems that can be affected by any fumes, not just those from nonstick cookware. For this reason, it's a good idea to keep birds out of the kitchen. Second, don't heat PFTE-coated pans beyond 500 degrees Fahrenheit (260 degrees Celsius) or leave them unattended [source: DuPont]. It's also a good idea to replace your pans if their coatings are visibly deteriorating.
Newer nonstick technologies also offer an alternative to PTFE -- we'll look at a few of them next.
New Nonstick Technologies
For decades, fluoropolymer nonstick coatings have ruled the market, but within the last couple of years, a few new technologies have appeared on the scene. Most of these are based on two related technologies -- silicon ceramics and silicone. Cuisinart's Ceramica, for example, is a nonstick ceramic that was first used in its GreenGourmet line. The coating does not contain PTFE or PFOA.
Another ceramic nonstick coating is Thermolon. The coating is mostly composed of silicon and oxygen. It is applied as a single layer over the metal of the pan and then followed by a protective or decorative top coat [source: Phillips]. The manufacturer promotes the new technology as PTFE-free and more eco-friendly due to less energy usage during the production process [source: Phillips]. Thermolon has a number of different formulations of its coating for specific nonstick cookware needs. GreenPan brand cookware uses Thermolon technology for its nonstick surface [source: GreenPan].
Another technology is silicone-based. You've probably seen or used silicone bakeware -- a product called NP2takes advantage of silicone's slipperiness to create a PTFE-free nonstick coating [source:AkzoNobel]. Tramontina's new Eco-friendly Cookware line uses the NP² nonstick technology. The company states that this cookware can be used to both sear and brown foods as well as used in the oven up to 350 degrees Fahrenheit (177 degrees Celsius) [source: Tramontina USA].
Thermolon technology arrived on the U.S. market in 2007, while Ceramica technology and NP² became available to consumers in 2008. Due to the relatively short time these new technologies have been on the market, little research has been done on their performance. However, it's clear that in the decades since the discovery of PTFE, technology continues to make food preparation an easier and faster process.