Searing and sautéing, and the pan sauce

Put four chicken thighs, skin down, into a frying pan that is a little too small for them. For the first minute they sizzle loudly. Then the sound drops to a mutter, liquid seeps out and pools around them, and five minutes later the skin is pale, wet and soft. Cook the same four thighs in a pan with room between them, and the sizzle keeps going, the skin turns deep brown and crisp, and there are brown bits stuck to the pan that you can make a sauce from.

Same chicken, same heat, same fat. The only difference is how much water was on the surface and how fast it could leave. This lesson is about that water. Lesson 2 showed that a wet surface can't get much above 100°C, and that browning needs a surface well above that. Everything a cook does to get a good sear follows from those two facts: drying the food, giving it room, heating the pan first, and knowing when to salt. So does the sauce you make afterwards, because the brown bits it is built on only form where the surface got hot. On the way you'll test three things people are told about steak, look at what the metal of a pan does, and sort out the argument about nonstick coatings.

Searing and sautéing are the same thing at different scales. You sear a large piece (a steak, a chicken thigh, a slab of tofu) to brown its surface. You sauté smaller pieces (sliced mushrooms, diced chicken, green beans) in a little fat, moving them around. Both are dry heat in a hot pan, and both fail the same way.

Why a crowded pan steams

Start with lesson 2's two facts. Water at ordinary pressure can't get hotter than its boiling point, so a surface that is wet sits near 100°C (212°F) while the water on it turns to steam. Browning, the Maillard reaction between amino acids and sugars, gets going fast at about 285°F (140°C) and above, as the Kansas State extension page lesson 2 used puts it.²⁰ Lesson 2 called that figure a rough mark rather than a switch, and it still is. Nothing below turns on the exact number, only on the gap between it and 100°C.

Now put cold, wet food into a hot pan. Two things happen at once. The food takes heat out of the pan, and it gives up water: water on its surface, and more that the heat drives out of the cut flesh. The pan has to boil that water away before the surface can climb past 100°C. With one or two pieces and plenty of room, the pan has heat to spare, the water flashes off, and the surface starts to brown within a minute or so. Crowd the pan and the sums change. There's more cold food drawing heat from the metal, more water arriving, and less open pan around the pieces for the steam to escape from. The pan's temperature drops, the water arrives faster than it can leave, it collects in a puddle, and now the food is simmering in its own juice.

America's Test Kitchen (ATK) describes exactly this in a review of frying pans. "If you try to cook four steaks in a 12-inch skillet that has a cooking surface diameter of 8 inches, for example, the pan will struggle to recover its heat, so one side of the steaks will come out gray and steamed with sparse fond that will make paler, weaker pan sauce."² An 8-inch cooking surface is about 20 cm across. Fond is the brown residue on the pan, which comes back later in this lesson. The same review marks down pans with tall, straight sides for the same reason: "These trapped condensation, steaming food instead of allowing it to lose moisture and encouraging browning."²

That last point is the real cost, and it's why the rule is about meat. The water has to go before the surface browns. While you wait for it, heat keeps travelling into the middle of the piece, as lesson 2 showed. A thin piece of chicken or steak can be cooked through, or past it, before its surface ever gets dry. So in meat, crowding does not just cost you colour and flavour. It costs you the texture inside, because you end up choosing between a pale outside and an overcooked middle. Hold on to that, because it is the reason the rule fails for mushrooms later on.

Four ways to keep the surface dry

Once you see the problem as water, the fixes are all ways of getting rid of it, or not adding it.

Dry the surface. Pat meat, fish or tofu with paper towels before it goes in. It sounds too small to matter. A 2019 newspaper column by Audrey Wilson, reporting J. Kenji López-Alt's tests, puts it strongly: "Simply blotting your steak with paper towels before searing it will improve it far better than any amount of room temperature resting will."⁶ The same column says the driest surface of all comes from leaving the meat uncovered on a rack in the fridge for a night or two.⁶ That raises a safety question, which the next section takes up.

Give it room. Leave space between pieces, and if they won't fit with space, cook in batches. Keep the finished pieces warm on a plate while the next batch browns. A pan with a wide, flat base and low sides helps, for the reasons ATK gives above.

Heat the pan first. Put the pan on the heat with its fat before the food goes in, and wait until the fat shimmers: its surface starts to ripple and move, like air over a hot road. A pan that is still warming up is a pan that can't boil off the water. How long a pan needs depends on what it is made of, which is the section on pans below.

Salt at the right time. Lesson 3 showed salt drawing water out of a cut tomato. It does the same to the surface of meat. Salt a steak or a chicken thigh and leave it a little while, and its surface turns wet with salty liquid, which is exactly what a sear doesn't want. Given longer, the meat takes that liquid back in. Wilson's column describes salting ahead as "long enough to let salt draw out liquid and then for that liquid to be re-absorbed leaving a dryer surface".⁶ The exact minutes come from López-Alt's own trials, which this course read only at second hand, so it does not print them. The rule that follows is simple: salt right before the meat goes in the pan, or well ahead (overnight is best), and not in between. Lesson 3's point still holds: taste the finished dish and adjust.

Drying meat in the fridge, and the rule it runs into

This is a small case of the course's question, which lesson 1 introduced: what is this rule protecting, and does it apply here? Lesson 4 gave you the two regulators' rules for raw meat in the fridge. FSIS: "Raw meat, poultry, and seafood should be in a sealed container or wrapped securely to prevent raw juices from contaminating other foods."²⁴ The FSA says to keep it "in their packaging or in clean sealed containers on the bottom shelf of the fridge".²⁷ The dry-surface method asks you to leave meat uncovered, so it departs from both. FSIS says what its wrapping is for: to stop raw juices reaching other food. If you want the dry surface anyway, the arrangement that keeps that goal is a rack over a tray or plate that catches every drip, on the bottom shelf, with nothing touching it. Be clear about what that is: this course's way of meeting the purpose FSIS states, not a regulator's instruction, and neither regulator's page read here mentions the method. If your fridge can't give it a shelf to itself, or you'd rather follow the rule as written, salt just before cooking instead and pat dry. That is the default in this lesson.

Chicken thighs, seared, and a sauce from the same pan

The whole technique fits on one dish, with a reason for each step. You'll need four skin-on chicken thighs, a heavy frying pan (not nonstick, for a reason you'll see), a wooden spatula, a small whisk or a fork, your thermometer from lesson 2, a little oil, a shallot, about 250 ml (1 cup) of chicken stock in a measuring jug, two tablespoons of cold butter, salt and pepper, and a lemon.

Before anything, set up for raw chicken the way lesson 4 did: clear the sink, cut the shallot and anything for a salad first, and only then open the chicken. Wash your hands and the board after the chicken, before you touch anything else.

1. Dry and salt. Pat the thighs dry with paper towels and bin the towels. Salt them now, just before they go in. (The overnight rack above is the alternative, if you've decided it suits your fridge.)
2. Heat the pan. Put the pan on medium-high with a thin film of oil, and wait until the oil shimmers.
3. Skin side down, with room. Lay the thighs in skin side down with a gap between each. If they touch, use two pans or do two batches. You should hear a steady sizzle. If it fades to a hiss and liquid pools, the pan is too full or not hot enough.
4. Leave the skin alone until it's brown. Skin has fat under it that melts out and crisps the skin as it goes, so it wants time on this side, at a heat that keeps it sizzling without burning. Turn the heat down a notch if it's darkening too fast. When the skin is deep golden and lets go of the pan easily, turn the thighs.
5. Cook to temperature, not to time. Finish the thighs on the second side, turning the heat down to medium if the outside is getting ahead of the inside, until they're done by your country's rule from lesson 4. In the US, that is 165°F (73.9°C) in the thickest part, away from the bone.²¹ In the UK, the FSA's cues are to cut into the thickest part and check "there is no pink meat left and that juices run clear", and that the meat is steaming hot.²² Move them to a plate, skin side up. ATK suggests tenting the meat loosely with foil, and says the loose seal "will help to keep any crust that has formed from turning soggy."³

Now look at the pan. Stuck to its base are brown patches. That is fond. ATK's page on pan sauces defines it in passing: "The base of a pan sauce is the fond, or browned bits, clinging to the bottom of the skillet after sautéing or searing meat, poultry, or fish."³ It's the Maillard reaction's work, concentrated, and it's the whole flavour base of what comes next.

6. Pour off most of the fat. Tip it into a small bowl, leaving a spoonful. Soften the shallot in it for a minute over medium heat.
7. Deglaze. Pour in the stock and scrape the fond up with a wooden spatula as the liquid bubbles. It dissolves into the stock and colours it. That is deglazing. Use low-salt stock if you can; ATK's reason is that "reduction can result in overwhelming saltiness."³ Wine works here too. How much of its alcohol survives a few minutes' simmering is a question with an answer, and lesson 8 gives it.
8. Reduce. Let it boil until it's noticeably thicker and has shrunk well down. ATK's way of checking: pour it back into the measuring jug it came from, and "the reduced liquid can be poured back into the cup toward the end of simmering to gauge if it has been adequately reduced."³ How far to take it is a matter of taste, so taste it.
9. Take it off the boil and whisk in cold butter. Turn the heat off or right down (that's this course's instruction; ATK's page doesn't give a heat for this step), and whisk in the butter a piece at a time, each piece melting before the next. ATK says to cut it in tablespoon-size chunks and gives the reason for using it cold: "Cold butter is easier to incorporate into a sauce than softened butter and it makes for a sturdier emulsion that is more resistant to separation."³
10. Season and balance. Taste. Add salt if it needs it, and a squeeze of lemon if it tastes heavy, which is lesson 3's acid doing its job against fat. Pour it over the chicken.

Step 9 is the one lesson 5 prepared you for. The finished sauce is an emulsion: fat from the butter held as fine droplets through the reduced stock. Lesson 5 showed that an emulsion stays together while its droplets are kept apart, breaks when they merge, and can sometimes be brought back by whisking the broken mixture slowly into a little water. ATK tells you that cold butter makes the sturdier emulsion. It does not say, on the page this course read, exactly what happens if you boil the finished sauce hard, and neither does any other source here. The research notes for this course expected it to split into a greasy layer, but that was reasoning, not a test. The practice at the end of this lesson has you boil a spoonful and see for yourself.

Why not nonstick for this? ATK again: "A nonstick skillet will not develop fond to the same degree as a traditional skillet will, and, because fond supplies a pan sauce with richness and depth of flavor, a nonstick skillet will make a less flavorful pan sauce."³ And crowding costs you twice here: "If it is overcrowded, the food will steam and will fail to create much fond."³ The pale, crowded thighs from the opening of this lesson would have left you nothing to deglaze.

For a meat-free version of the same dish, sear thick slices of firm tofu, patted very dry, or big pieces of mushroom, then deglaze the pan with vegetable stock and finish it the same way. The next section explains why mushrooms need a different rulebook.

Mushrooms, where two rules fail

Mushrooms come with two rules. Don't wash them, because they'll soak up water and won't brown. And don't crowd them, for all the reasons above. Both turn out to be wrong for most mushrooms, and why they're wrong shows you what the rules were for.

Start with washing. ATK weighed white, cremini, portobello, shiitake, oyster and maitake mushrooms before and after a one-minute soak. "The mushrooms without exposed gills retained almost no water, while those with them soaked up as much as 25 percent of their weight in liquid."⁴ So a closed button or chestnut mushroom barely notices a rinse; an oyster mushroom or a big open portobello can take up as much as a quarter of its weight, and ATK says the water "prolongs cooking and makes it harder for them to brown."⁴ ATK's own bottom line is that for farmed mushrooms you often don't need to clean them at all: "Unless they’re foraged, most mushrooms do not need to be cleaned."⁴ Rinse closed ones just before cooking if they're dirty; brush or wipe the open-gilled kinds.

Now crowding. In 2009 Dave Arnold, who ran the Cooking Issues blog, set up a deliberately unfair test. "To make the test really severe, I decided to cook the soaked mushrooms in one batch in an extremely crowded pan, and the dry mushrooms in 3 batches with plenty of room. We weighed out identical amounts of salt and oil (this is the crucial part) and began cooking."⁵ The soaked, crowded batch turned into a soupy mess at first, as you'd expect. Then its water boiled off, and at the end, he wrote, "They looked as good and tasted better and less oily than their dry cousins".⁵ In a reply to a reader he added, "They browned quite well once the liquid in the pan evaporated."⁵ It was one test in one kitchen, tasted by the people who ran it, so treat it as a strong hint rather than a law. But the reason it came out that way is worth having.

That's the course's question doing its job. "Don't crowd the pan" is a real rule with a real mechanism, and the mechanism is about meat: a wet surface, and an interior that overcooks while it dries. "Don't wash mushrooms" protects a dry surface too, but the test says most mushrooms hardly take up water, and the ones that do can still brown once it's gone. Both rules are worth knowing, and both stop applying once you know what they're for.

Three things everyone is told about steak

Each of these is repeated in recipes and on cooking shows. Each has been tested, and none of the three survived as usually stated.

"Searing seals in the juices"

The idea is that a hot sear closes the surface, so the meat keeps its juice. ATK tested it on eight rib-eye steaks, each about 3 cm (1¼ inches) thick, in two batches. One batch was seared first in a hot pan, then finished in a 250°F (about 120°C) oven to 125°F (about 52°C) inside. The other went in the oven first, to about 110°F (about 43°C), and was then seared until it reached the same 125°F. Both were weighed before and after. "We found that both sets of steak lost nearly an identical amount of liquid: around 22 percent of their weight."¹ ATK's verdict: "The notion of sealing in juices is thus nothing but an old wives’ tale."¹ Eight steaks is a small test, but the result fits the physics: a crust is a dried, browned layer, not a waterproof skin.

What searing does do is the thing this lesson started with: it browns the surface, and browning is flavour, colour and a crisp texture. What controls how juicy the meat is, is how hot the inside gets, which is lesson 7's subject. The order ATK's second batch used, gentle heat first and a sear at the end, is called the reverse sear, and lesson 7 comes back to it.

"Let the steak come to room temperature first"

The idea is that meat straight from the fridge cooks unevenly, so it should sit out first. López-Alt's test, as Wilson reports it, put a probe in the centre of a thick strip steak straight from the fridge and watched it. "After 20 minutes, the temperature rose to less than 2 degrees. In fact, even after two full hours, the temperature had barely risen by 10 degrees".⁶ Those are Fahrenheit degrees: under about 1°C in 20 minutes, and about 5 or 6°C in two hours. A thick steak is a lump of mostly water, and heat moves into it slowly, as lesson 2 showed. Half an hour on the counter barely touches the centre.

To be fair to the other side, Wilson's column also reports Bon Appétit's view that meat left out before cooking gives "a juicier, more evenly cooked steak".⁶ The reasoning, as she reports it, is that a centre that starts warmer reaches its target sooner, so the meat nearer the surface has less time to overcook, and it matters most for thick cuts and whole birds. That's a real mechanism; the question is how much warming a realistic wait achieves. This course didn't read Bon Appétit's article, and Wilson left the choice to her readers. What the one measured test shows is how little the centre warms in the time people usually allow. Food safety sets the outer limit either way, and lesson 4 gave both countries' versions. FSIS says perishable food shouldn't be left out more than 2 hours, or 1 hour above 90°F (32°C).²³ The FSA allows chilled food out during preparation for "a maximum of four hours".²⁷

"Flip it only once"

The idea is that leaving the meat undisturbed is the only way to build a crust. A 2026 Serious Eats article by Leah Colins reports two sets of tests that found otherwise. The food scientist Harold McGee showed that frequent flipping browns as well as a single flip, and López-Alt tested it on burgers: "Burgers flipped every 15 seconds browned just as well as those flipped once, cooked in about two-thirds the time, and had roughly 40% less overcooked meat around the edges."⁷ McGee's own writing on it wasn't read for this course; this is Colins's account of it.

The mechanism is heat going in from both sides at once. In Colins's words, "Every time you turn the steak, the hotter side faces upward and sheds some of its stored heat into the surrounding air while the cooler side gets its turn against the skillet."⁷ A single flip lets heat pile up under one face for minutes, and Colins credits frequent flipping with less of "the gray, overcooked meat that often forms just beneath the surface."⁷

Colins is careful about the size of the effect, and so should you be: "Kenji points out in his testing that flipping only once won't ruin your steak, and frequent flipping won't transform a mediocre steak into the best one you've ever eaten. The differences are noticeable but a bit subtle".⁷ So this one isn't a myth that ruins dinners. It is a rule that gives up a little evenness for nothing. Flip as often as you like; flip once if you're busy.

Pans: what the metal does

A pan has two jobs with heat. It has to spread the heat of a burner sideways, so the whole base is hot and not just a ring over the flame, and it has to hold enough heat that cold food going in does not drop its temperature too far. Different metals are good at different halves of that.

The first job is conduction, which lesson 2 described. How well a metal conducts is measured as its thermal conductivity. Here are the figures from Engineering ToolBox's table for the metals pans are made of.⁸

Figures from Engineering ToolBox's table of metal conductivities, at 0°C for copper and aluminium and 20°C for the rest.⁸ The aluminium bar is the pure metal; the same table gives common aluminium alloys at 150 to 190, and which alloy a given pan uses wasn't read. Carbon steel is the 0.5% carbon grade; stainless is type 304. Bar lengths are to scale.

Copper and aluminium spread heat fast. On a burner that only heats a ring, a copper or aluminium base carries that heat out to the edges before food has a chance to notice, and when you turn the flame down the pan answers quickly. Cast iron and carbon steel conduct a little under a quarter as well as pure aluminium, so a cast-iron pan on a small burner heats in the middle first and is cooler at the rim until you give it time. Stainless steel on its own is poor, about a sixteenth of aluminium.

The second job, holding heat, depends mostly on how much metal there is. A cast-iron pan is thick and heavy, so once it's hot it holds a lot of heat, and a steak dropped into it takes the pan's temperature down less than it would in a thin pan. That is why cast iron has its reputation for searing, despite conducting poorly. It pays for both halves in one way: it needs a long, patient preheat to get even, and it is heavy. This course hasn't read a tested preheat time. A common cook's check, not one from a source read here, is to heat it over medium until a drop of water skitters across the whole base rather than just the middle.

Good stainless pans get round stainless steel's poor conduction by being clad: a layer of aluminium bonded between two layers of stainless. ATK's review explains the trade: "Aluminum conducts heat quickly, making the pan responsive to temperature changes; steel conducts slowly and retains heat, so the pan cooks remarkably evenly across its surface."² The steel faces the food for a second reason: "Aluminum reacts to acidic foods, but stainless steel doesn’t, so you can cook anything without fear of flavor transfer and damage to the pan."² That is ATK's statement about bare aluminium and acid, a matter of taste and the pan's surface.

A heavy clad stainless pan or a cast-iron one is the "heavy frying pan" lesson 1 asked you to have. Either will sear and make a pan sauce. The next two sections are about looking after them, and about the other pan most kitchens have.

Cast iron: what it needs, and what it doesn't

Cast iron comes with more folklore than any other pan. The maker, Lodge, is the clearest source, and it contradicts most of it.

Start with what the slick black surface is. "Seasoning is just oil baked onto the pan through a process called polymerization," Lodge says: heated oil turns from a liquid into a hard, bonded layer.⁹ Every time you cook with fat, a little more builds up, and "Over time, these layers build up to form a strong, nonstick cooking surface."⁹ So a well-used pan does release food well. The myth is the word "naturally". The slickness is oil, built up by use; a new pan with a thin seasoning, or one that has been stripped, sticks.

Soap is the big one. Lodge's cleaning page tells you to "Start with warm, soapy water and scrub with a stiff-bristled brush or scrubbing pad", and answers the question directly: "Soap is totally okay! The soap we use for washing dishes today is no longer strong enough to remove seasoning from cast iron and is an easy way to prevent build up."⁹ Then dry it straight away and oil it: "Dry completely with a paper towel or lint-free cloth." "Add a thin layer of oil, using a paper towel to distribute it over the entire surface."⁹

What does damage it is water left sitting, and the dishwasher. On soaking: "No! Soaking cast iron in water is a recipe for rust." On the dishwasher: "A dishwasher will remove the seasoning and likely cause rust."⁹ Rust isn't the end of a pan; Lodge's page gives a scrub-and-re-season method that ends with the pan upside down in an oven at 450 to 500°F (about 230 to 260°C) for an hour.⁹

Acid is the last one, and here the old rule has something in it. Long, acidic cooking can wear seasoning and make food taste of metal. But Lodge draws the line by time: "As a general rule, you shouldn’t leave acidic ingredients directly in cast iron for more than about 45 minutes," and "Similarly, deglazing your pan with wine or adding a little lemon juice to your dish shouldn’t cause problems."⁹ Lodge's seasoning page adds one condition: acidic recipes "aren’t the best choice for new cast iron because they can break down seasoning," and once the seasoning has built up, it says, you can cook acidic ingredients "with cook times under 45 minutes."⁹ So in a pan with some seasoning on it, a pan sauce finished with lemon is fine. A tomato sauce left to simmer all afternoon belongs in another pot. ATK found the same from the sauce's side: a pan sauce made in well-seasoned cast iron "tasted fine", while "Poorly maintained cast iron, however, will yield a metallic-tasting sauce."³

Nonstick pans: three questions, not one

Most kitchens also have a nonstick pan, and most people have heard that nonstick coatings are dangerous. The coating on a conventional nonstick pan is PTFE (polytetrafluoroethylene, sold under names such as Teflon). C&EN counts PTFE as one of a large family of chemicals called PFAS, some of which build up in the body and the environment.¹² The cookware industry objects that putting a large, inert polymer in the same bag as those small molecules is where the scare comes from, and you'll meet that argument in its own words below.¹³ The argument about nonstick pans is really three arguments folded together, and they have different answers.

First: does an intact pan, used normally, put PFAS into your food? The US Food and Drug Administration (FDA), which authorises materials that touch food, says on its PFAS page that the coating is applied to the pan at very high temperatures and that "The manufacturing process vaporizes off virtually all the smaller (i.e., migratable) PFAS molecules." Its conclusion: "Studies show negligible amounts of PFAS in this coating can migrate to food."¹⁰ Of the uses of PFAS in contact with food that it authorises, the FDA says "only paper and paperboard agents would result in dietary exposure to PFAS that may result in a potential safety concern", and those grease-proofing agents are no longer sold into the US market.¹⁰ The European Food Safety Authority's 2020 announcement, on the four PFAS its assessment focused on (PFOA among them), says that in food these substances "are most often found in drinking water, fish, fruit, eggs, and egg products."¹⁶ That is a list of foods, so it can't tell you anything about pans either way, and the announcement read here doesn't discuss cookware.

The chemical most people have heard of, PFOA, was a processing aid used in making PTFE rather than the coating itself, though C&EN reports that the coatings made with it "contained residual traces of the molecule."¹² The US Environmental Protection Agency (EPA) ran a programme with eight major manufacturers whose second goal was "To commit to working toward the elimination of these chemicals from emissions and products by 2015", and says "All companies have met the PFOA Stewardship Program goals."¹¹ The New Lede reports that Chemours, which makes the Teflon coating, stopped using PFOA in 2015 and switched to another PFAS processing aid, called GenX.¹⁴ That replacement is part of the third argument, below.

The FDA's finding covers an intact coating. Coatings scratch and flake with wear, and here the two sides say different things, both reported in The New Lede. Chemours, the coating's maker, says on its website that swallowed PTFE flakes are "non-toxic and would pass through the body without being absorbed", in the article's report of it. David Andrews of the Environmental Working Group, an environmental nonprofit, half agrees: "The bulk plastic material will likely largely pass through the body, but it’s a matter of how many small fragments will break off in the body," and "I’ve seen no studies looking at that, specifically."¹⁴ So on this first question, the regulator's answer is clear, and the evidence it rests on is about new, intact coatings.

Second: is an overheated pan harmful? Yes, and nobody in this argument disputes it. C&EN, the American Chemical Society's news magazine, puts it plainly: "PTFE degrades when it’s heated above 260 °C, releasing smaller PFAS molecules into air and food." And: "The fumes are also fatal to birds. But cases of such effects are uncommon, and it is unclear whether exposure from regular use harms human health."¹² In people the fumes can cause a short flu-like illness. The coating's maker, Chemours, according to The New Lede's report, warns against preheating an empty nonstick pan on high heat.¹⁴ This course's reading of why, from lesson 2 rather than from a source: in an empty pan on a high flame there's no food or liquid taking the heat away, so nothing stops the coating climbing past 260°C. So use nonstick at low to medium heat, never preheat it empty on high, keep the kitchen ventilated, and if you keep a pet bird, keep it well away from the kitchen. This is also why nonstick is the wrong pan for a hard sear.

Third: should PTFE cookware be sold at all? This is where the real disagreement is, and it is only partly a question about your kitchen. It's about pollution where fluoropolymers like PTFE are made and where they end up.

The industry's case, in the words of the Cookware Sustainability Alliance, a cookware industry nonprofit that has campaigned against the bans: PTFE has been studied for decades, and authorities "consistently conclude it is an inert molecule that is non-bioaccumulative, insoluble in water, non-toxic, and therefore safe for consumers." It adds that "The same compounds used in non-stick cookware (PTFE) are also used in life-saving medical devices, such as pacemakers."¹³ Its president, Steve Burns, argues that the bans target a problem already solved: "Folks who are looking to ban nonstick cookware now are seeking to right the wrongs of the past."¹²

The case for restriction, in the words of its supporters, is about manufacturing, not the pan on your stove. Rainer Lohmann, who directs a PFAS research centre at the University of Rhode Island, told The New Lede: "I don’t see manufacturers being able to produce [Teflon pans] without adding contamination to the environment."¹⁴ Gillian Miller of the Ecology Center, a US environmental nonprofit, told C&EN that PTFE coatings are probably a lower exposure hazard for most people than other sources, but that "If you ignore that and say we made this inert polymer, you completely ignore the manufacturing impact."¹² The Los Angeles County Sanitation Districts, which treat the county's wastewater, wrote in support of California's proposed ban that "Acting boldly to turn off the spigot of PFAS in consumer products is the only meaningful and cost-effective way to potentially avoid further PFAS contamination and avert the need for expensive treatment systems".¹⁴

Notice that the two sides partly talk past each other. The Alliance mostly talks about the finished polymer in your kitchen; the ban's supporters mostly talk about the factory and the landfill. Both can be right about what they're describing. But they do disagree on one factual point: whether making PTFE today still pollutes. The Alliance says the problem was solved when PFOA went: its site says "The problematic PFAS (like PFOA) were never used on cookware and were banned from chemical production over a dozen years ago."¹³ The other side points at the replacement. The New Lede reports that a 2021 EPA assessment found GenX "highly toxic at small doses" (the journalist's words; this course didn't read the assessment), and Miller told C&EN that making fluoropolymers still "requires the use of PFAS molecules with unknown toxicity risks", in C&EN's paraphrase of her.¹²¹⁴ Beyond that factual point, the disagreement is over which of these should decide whether a pan is sold, and that is partly a value question. What would settle the factual part is data on emissions across a pan's whole life, from manufacture with today's processing aids to disposal, which this course hasn't found.

The law is moving, and these are the facts as of September 2026. Minnesota banned the sale of cookware with intentionally added PFAS from January 2025, and Colorado and Maine from January 2026, according to a law firm's summary written that month.¹⁵ Connecticut, since July 2026, lets such cookware be sold only if the maker has notified the state and labelled it, and bans it outright from January 2028, according to the state's environment department.²⁸ California's legislature passed a ban in 2025 and the governor vetoed it on 13 October, citing concern about affordable cookware.²⁵ In Europe, C&EN reported in 2025 that France's PFAS ban, due in 2026, leaves cookware out, and the European Union's broad PFAS restriction hadn't been adopted when this course was researched.¹²²⁶ This paragraph will date; check your own state or country.

So what should you do? This course's reading of the sources is that both of these choices are defensible:

• Keep an intact nonstick pan for eggs, fish and other delicate things, use it at low to medium heat, never heat it empty on high, and replace it when the coating is scratched or flaking.
• Do without, and use cast iron, carbon steel or clad stainless, for reasons of durability or of the environmental argument above. A well-seasoned cast-iron or carbon-steel pan and a little more fat handle most of what nonstick does.

One caution if you shop for a replacement: "ceramic" nonstick coatings are made differently, but C&EN reports that "Users often complain that ceramic coatings lose their nonstick property sooner than PTFE does. Scientific reviews are mixed," and quotes Kevin Golovin, an engineering professor at the University of Toronto, warning that some pans sold as ceramic still carry PFAS; his advice is to look for the label "fluorine-free".¹²

Aluminium pans and dementia

One more worry, briefly, because people still ask. The idea that aluminium pans cause Alzheimer's disease goes back to a 1965 study in which rabbits injected with aluminium developed tangles in their brains. The UK's Alzheimer's Society says "Importantly, these results were only seen with extremely high doses - far more than we normally get from our environment," and that aluminium in food is poorly absorbed.¹⁷ It is fair about the loose ends: "Other studies have suggested that high aluminium exposure might be related to an increased risk of dementia. These studies are small and others contradict them." Its conclusion: "No convincing relationship between aluminium and the development of Alzheimer's disease has been established."¹⁷ Bare aluminium does react with acid, as ATK said above, which is a reason to cook a long tomato sauce in something else, and a matter of flavour.

Stir-frying: the same idea in a different pan

Stir-frying is the dry-surface lesson taken as far as a home kitchen can take it. ATK's Lan Lam opens her article on the wok with the definition from Buwei Yang Chao's 1945 book How to Cook and Eat in Chinese, which Chao offers "roughly speaking": "ch’ao may be defined as big-fire-shallow-fat-continual-stirring-quick-frying of cut-up material with wet seasoning."¹⁸ Every part of that phrase is this lesson. Big fire drives water off fast; small pieces have lots of surface and little inside; constant movement keeps each piece from sitting in its own steam.

Lam describes a wok as having two zones. At the bottom, the "SEAR ZONE" is the hottest part and food passing through it browns; a couple of inches up, a "STEAM ZONE" forms where moisture escaping from the food is held by the tall sides, and helps it cook through.¹⁸ In her tests over gas, beef stirred constantly cooked about twice as fast as beef stirred only now and then, and she notes that woks behave differently on electric and induction hobs.¹⁸

Most home cooks stir-fry in a frying pan, and there the crowding rule comes straight back. ATK's technique for stir-frying without a wok says "Even a skillet set over high heat won’t get hot enough to quickly stir-fry either large amounts or large pieces of food," so cut the food small and cook a little at a time, and "If necessary, cook the protein in batches to avoid overcrowding the pan, which will cause the protein to steam rather than sear."¹⁹ That page is written for a nonstick skillet, and says to heat the oil "until just smoking". It doesn't say how hot that is, and no source read here compares it with the 260°C at which C&EN says PTFE starts to break down. So if you stir-fry in nonstick, never let the pan heat empty, and a cast-iron or clad stainless pan takes the question away. Then, oddly, it gives the opposite advice to Lam on stirring: "And despite the name, don’t stir constantly. Leaving it alone will let your stir-fry brown and caramelize."¹⁹ The two pieces are from the same test kitchen, about different pans on what may be different heat, and neither mentions the other. This course's reading is that a flat pan on a home burner needs the food left still for a while to brown, because it does not have a wok's searing zone to pass through, but that's an inference, not a test. Try both and see what your pan does.

A stir-fry of beef strips or cubes of firm tofu with vegetables, then, goes like this. Everything cut and the sauce mixed before the pan goes on (lesson 1's mise en place, since the whole thing takes minutes). Beef or tofu patted dry. The protein browned in batches in a very hot pan with a little oil, each batch moved to a bowl. The vegetables next, the hardest first. The aromatics (garlic, ginger) last, briefly, because they burn. Then the protein back in, and the sauce, tossed until it coats and thickens. Lesson 12 takes a stir-fry recipe apart into exactly these steps and cooks it with whatever vegetables you have.

What people get wrong

"Searing seals in the juices." Seared-first and seared-last steaks lost about the same share of their weight in ATK's test.¹ Searing is for flavour and texture; juiciness is about how hot the inside gets.

"Let the steak come to room temperature first." Its centre barely warms in the time people allow.⁶ Dry it instead, and keep to lesson 4's 2-hour limit.²³

"Flip it only once." Frequent flipping browns as well and cooks a little more evenly, though the difference is modest.⁷

"Never crowd the pan," applied to everything. It's a rule about meat, whose inside overcooks while the water goes. Mushrooms can take it, on Arnold's test.⁵ (Onions you want soft is this course's reasoning from the same mechanism, not a test.)

"Never wash mushrooms." Closed mushrooms take up almost no water; wipe the open-gilled kinds.⁴

"Never use soap on cast iron." The maker says soap is fine; soaking and the dishwasher are the problems.⁹

"Cast iron is naturally non-stick." It's non-stick once oil has built up on it by use, not before.⁹

"Nonstick pans put chemicals in your food" and its mirror, "Nonstick is fine at any heat." An intact coating at normal heat releases negligible amounts, by the FDA's reading; an overheated one breaks down above 260°C.¹⁰¹² Whether it should be sold is a separate, open argument.

"Aluminium pans cause Alzheimer's." The Alzheimer's Society says no convincing link has been established.¹⁷

Practice

Connections

Lesson 2 gave you water's ceiling and the centre that lags; this lesson turned both into how to sear, why crowding costs meat its texture, and why a thick steak barely warms on the counter. Lesson 3's salt came back as the reason to salt right before or well ahead, and its acid finished the sauce. Lesson 4's order of work set up the raw chicken, and its fridge rule met the dry-surface method halfway. Lesson 5's emulsion is what cold butter makes in a pan sauce, and the reason to suspect a hard boil, which the practice has you test.

This lesson dealt with the surface. Lesson 7 moves to the centre: how a roast keeps cooking after it leaves the oven, why resting is really about temperature, and the reverse sear that ATK's steak test used. Lesson 8 tells you how much alcohol survives a deglaze with wine. Lesson 10 comes back to the pan sauce next to the stocks and starch-thickened sauces, and lesson 12 takes a stir-fry recipe apart.

Go deeper

• America's Test Kitchen, Pan Sauces 101. Read in full for this course. The whole method with the kit laid out, including the measuring-cup check for judging a reduction.
• Dave Arnold, "Crowded Wet Mushrooms. A Beautiful Thing.", Cooking Issues, 2009. Read in full, with the comments. Short, and a good model of how to test a kitchen rule: same salt, same oil, one variable changed.
• Lan Lam, "The Science of Stir-Frying in a Wok", America's Test Kitchen, 2020. The public part read in full. The two zones of a wok, and a stirring test with an infrared camera.
• Prachi Patel, "How does nonstick cookware work, and should you switch to 'green' pans?", C&EN, 2025. Read in full. The chemistry of PTFE and ceramic coatings, with people on both sides of the argument quoted directly.
• Lodge, How to Clean and How to Season. Both read in full. The maker's own instructions, including rust removal.

Sources

1. America's Test Kitchen, "Searing Steak", Cook's Illustrated how-to, no author or date, https://www.americastestkitchen.com/cooksillustrated/how_tos/5699-searing-steak . Read level: full, directly. Supports: the eight-steak test, its oven temperature and end temperatures, 22 percent, and the "old wives’ tale" verdict. "A crust is a dried, browned layer, not a waterproof skin" is this course's reading, as is "fits the physics".
2. America's Test Kitchen, "The Best Stainless-Steel Skillets", equipment review, dated 25 June 2025 in the page's metadata, https://www.americastestkitchen.com/equipment_reviews/1944-12-inch-stainless-steel-skillets . Read level: the review text, directly. Supports: the four-steak crowding quotation, tall sides trapping condensation, clad construction, and aluminium reacting with acid.
3. America's Test Kitchen, "Pan Sauces 101", no author or date, https://www.americastestkitchen.com/cooksillustrated/how_tos/5551-pan-sauces-101 . Read level: full, directly. Supports: fond, deglazing, reducing and butter; nonstick and crowding leaving less fond; low-sodium stock; the measuring cup; tenting loosely; well-seasoned cast iron tasting fine and poorly kept cast iron tasting metallic (Gate closures, lesson 6, and the Stage 4 note, lesson 6); cold butter. It says nothing about boiling the finished sauce or about the heat for adding butter, as the body says.
4. America's Test Kitchen, "Should You Wash Mushrooms? The Definitive Answer", no author or date, https://www.americastestkitchen.com/how_tos/11827-should-you-wash-mushrooms . Read level: full, directly. Supports: the one-minute soak, almost no water against 25 percent, exposed gills slowing browning, most farmed mushrooms not needing cleaning, and "virtually impossible to overcook".
5. Dave Arnold, "Crowded Wet Mushrooms. A Beautiful Thing.", Cooking Issues, 21 December 2009, https://cookingissues.com/2009/12/21/crowded-wet-mushrooms-a-beautiful-thing/ . Read level: full, directly, with the comments. Supports: the test's design, the result, and his reply of 22 December 2009 on browning.
6. Audrey Wilson, "Let's Talk Food: Steaks at room temperature or not?", Hawaii Tribune-Herald, 19 February 2019, https://www.hawaiitribune-herald.com/2019/02/19/features/lets-talk-food-steaks-at-room-temperature-or-not/ . Read level: full, directly. A newspaper column reporting J. Kenji López-Alt's test; López-Alt's Serious Eats original was not read. Supports: the temperature rise, blotting, drying uncovered on a rack, the salting timing (whose minutes the lesson leaves out), and Bon Appétit's opposing view as Wilson reports it.
7. Leah Colins, "For the Juiciest Steaks With the Best Crust, I Always Break This Classic Cooking Rule", Serious Eats, syndicated on Yahoo, 15 July 2026, https://www.yahoo.com/lifestyle/articles/juiciest-steaks-best-crust-always-210000151.html . Read level: full, directly. Supports: McGee's finding and López-Alt's burger test as she reports them, the mechanism, the grey band beneath the surface (Stage 4 note, lesson 6), and the "a bit subtle" caveat. McGee's own column was not read.
8. Engineering ToolBox, "Metals, Metallic Elements and Alloys: Thermal Conductivities", https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html . Read level: the table, directly. Supports: every figure in the chart and the alloy range. "About a quarter" and "about a sixteenth" are this course's arithmetic from the table.
9. Lodge Cast Iron, "How to Clean", "How to Season", "3 Tips for Cooking Acidic Foods in Cast Iron" (dated 11 February 2025 in the page's metadata) and "10 Myths About Cast Iron Cookware, Busted!", https://www.lodgecastiron.com . Read level: all four, full, directly. Supports: seasoning as polymerised oil building to a nonstick surface, soap, drying and oiling, soaking, the dishwasher, re-seasoning at 450 to 500°F, acid and new cast iron, the 45-minute guide for acid and deglazing.
10. US Food and Drug Administration, "Authorized Uses of PFAS in Food Contact Applications", content current as of 3 January 2025, https://www.fda.gov/food/process-contaminants-food/authorized-uses-pfas-food-contact-applications . Read level: full, directly. Supports: manufacture vaporising migratable molecules, negligible migration, paper and paperboard as the only use of concern, and grease-proofers no longer sold.
11. US Environmental Protection Agency, "Risk Management for Per- and Polyfluoroalkyl Substances (PFAS) under TSCA", last updated 26 March 2026 . Read level: full, directly. Supports: the eight companies, the goal of working toward elimination by 2015, and "All companies have met" the goals.
12. Prachi Patel, "How does nonstick cookware work, and should you switch to 'green' pans?", C&EN, 2025 . Read level: full, directly. Supports: PTFE as a PFAS, PFOA's residual traces in older coatings, 260°C, the fumes and birds, uncommon cases, Burns's and Miller's quotations and the paraphrase of Miller on processing aids, the ceramic coatings and Golovin, and France's ban leaving out cookware as the article reported it in 2025 (Stage 4 note, lesson 6). The "short flu-like illness" is from the Shimizu case report in SOURCES D3a (abstract) and this article's "Teflon flu".
13. Cookware Sustainability Alliance, home page, https://cookwaresustainabilityalliance.org/ . Read level: full, directly. Supports: the three quotations, and its objection to calling PTFE a "PFAS forever chemical" (its July 2026 special report on the same page; Stage 4 note, lesson 6). That it has campaigned against the bans is from The New Lede's report (note 14) and the page's own account of state laws.
14. Shannon Kelleher, "Industry, environmental groups spar over California bill to ban PFAS in cookware", The New Lede, 29 September 2025, https://www.thenewlede.org/2025/09/california-cookware-pfas-ban/ . Read level: full, directly. Supports: Lohmann's quotation, the Los Angeles County Sanitation Districts' letter, Chemours' warning, its statement on flakes and its 2015 switch from PFOA to GenX as the journalist reports them, the 2021 EPA finding on GenX in the journalist's words, and David Andrews of the Environmental Working Group on flakes (Stage 4 note, lesson 6). Chemours' own page and the EPA assessment were not read.
15. Morgan Lewis, "State Regulation of PFAS in Consumer Products Continues to Gain Momentum in 2026", LawFlash, 21 January 2026 . Read level: full, directly. Supports: Minnesota from 1 January 2025, and Colorado and Maine from 1 January 2026. Its Connecticut paragraph runs the July 2026 notification rule together with the list of products, and is not used; note 28 is.
16. European Food Safety Authority, "PFAS in food: EFSA assesses risks and sets tolerable intake", 17 September 2020 . Read level: full; the quoted phrase rechecked directly. Supports: the four PFAS assessed and the foods they are most often found in.
17. Alzheimer's Society, "Metals and the risk of dementia", read through the Internet Archive's capture of 12 November 2025 . Read level: full, directly. Supports: the 1965 study and its doses, poor absorption, the small contradictory studies, and the conclusion.
18. Lan Lam, "The Science of Stir-Frying in a Wok", America's Test Kitchen, 1 April 2020 . Read level: full, directly (the public part). Supports: the two zones, the stirring test and its note on electric hobs, and Chao's definition with its "roughly speaking", which is quoted through Lam; Chao's book was not read.
19. America's Test Kitchen, "Technique #20: Make Superior Stir-Fries Without a Wok", 12 October 2023 . Read level: full, directly. Supports: small pieces and small amounts, cooking protein in batches, not stirring constantly, and that the page is written for a nonstick skillet with the oil heated "until just smoking". The reading of the two ATK pieces' disagreement is this course's, as the body says.
20. Nancy Honig, "The Maillard Reaction", Wild West District Extension Blog, Kansas State University Research and Extension, 15 August 2022 . Read level: full, directly. Supports: about 285°F (140°C), given as approximate, as lesson 2 gives it.
21. USDA FSIS, "Safe Minimum Internal Temperature Chart", last updated 14 April 2025, read through the Internet Archive's September 2026 capture . Read level: full. Supports: 165°F (73.9°C) for all poultry, thighs included.
22. Food Standards Agency, "Cooking your food", GOV.UK, https://www.gov.uk/government/publications/cooking-your-food/cooking-your-food . Read level: full. Supports: the visual cues for chicken and steaming hot.
23. USDA FSIS, "Danger Zone (40°F - 140°F)", last updated 28 June 2023, read through a 2026 Internet Archive capture . Read level: full. Supports: the 2-hour and 1-hour rules.
24. USDA FSIS, "Refrigeration and Food Safety", last updated 23 March 2015, read through the Internet Archive's 23 September 2026 capture . Read level: full, directly. Supports: the quoted wrapping rule and its stated purpose. The rack-over-a-tray arrangement is this course's, as the body says.
25. Keller and Heckman, "CA Governor Newsom Vetoes PFAS Ban in Cookware, All Food Packaging", National Law Review, 20 October 2025, https://natlawreview.com/article/ca-governor-newsom-vetoes-pfas-ban-cookware-all-food-packaging , and Farella Braun + Martel, note on the veto of California SB 682, 16 October 2025 . Read level: the first, directly, at Stage 4; the second, full at Stage 1 through a summarising fetch tool. Supports: the veto on 13 October 2025 and the affordability reason. The governor is not quoted.
26. Arnold & Porter advisory, 27 March 2026, and Bergeson & Campbell, 31 March 2026, on the EU's universal PFAS restriction . Read level: full, through a summarising fetch tool at Stage 1. Supports: the restriction not yet adopted; SOURCES records it as not adopted on 24 September 2026. Neither was rechecked for this lesson, and neither mentions cookware by name.
27. FSA, "How to chill, freeze and defrost food safely", GOV.UK, published 18 December 2017, https://www.gov.uk/government/publications/how-to-chill-freeze-and-defrost-food-safely/how-to-chill-freeze-and-defrost-food-safely . Read level: full, directly. Supports: raw meat in its packaging or sealed containers on the bottom shelf, and four hours out during preparation.
28. Connecticut Department of Energy and Environmental Protection, "PFAS in Products", https://portal.ct.gov/deep/p2/pfas-in-products . Read level: the page, directly, at Stage 4. Supports: notification and labelling from 1 July 2026, and the ban on cookware with intentionally added PFAS from 1 January 2028.