Why You Should Never Bake Cookies on an Aluminum Foil-Lined Baking Sheet
If you value your cookies' quality, you'll skip the foil.
There are dozens of fantastic ways to use aluminum foil in your kitchen — from covering your leftover lasagna before re-heating it in the oven to lining your grill to make roasting veggies easier and less messy. These are just a few of the myriad reasons foil has rightly earned its place as an essential kitchen staple you should always have on hand.
But if you've been reaching for the aluminum foil to line your baking sheets before making cookies or other sweet, doughy treats, you might be surprised to learn you've been committing a major baking faux pas.
The reason you should never bake cookies on an aluminum foil-lined baking sheet all boils down to science.
As you probably already know, foil used for cooking is made almost exclusively from the metal aluminum, which is a great conductor of heat and useful in many cooking techniques. Just to give you a point of reference, Reynolds Wrap Aluminum Foil is made of 98.5 percent aluminum. (Another thing to note: Cooking foil doesn't actually contain any tin these days, despite what the common misnomer "tin foil" would suggest. It's a nod to earlier times when tin was actually used in the product.)
And while these conductive properties are what make aluminum foil heat-safe and well-suited for use in the oven and other cooking applications, what you may not have realized is that this signature characteristic has some serious downsides when it comes to baking, whether you're making chocolate chip cookies, holiday gingersnaps, or any other delightfully doughy treat.
Ultimately, the scientific reason you should never bake cookies on a foil-lined baking sheet is simple: The parts of your cookie dough that come in direct contact with the foil are exposed to more concentrated heat than the rest of your cookies, thanks to aluminum's natural conductor properties.
The end result? Your batch of cookies ends up baking unevenly, with the bottoms of your cookies (which are in direct contact with the aluminum foil) baking faster than the tops (which are only exposed to the evenly distributed hot air in your oven). That's why cookies baked on foil-lined sheets have browner, crispier bottoms (that, yes, are sometimes burned) than those baked on parchment paper, the scientifically smarter choice for the perfect batch of cookies.
Indeed, parchment paper is the clear winner for all of your baking needs because, unlike foil, it distributes your oven's heat more evenly and keeps the highly-concentrated heat of your metal baking pan (or foil lining) from scorching the bottoms of your cookies. It also has a natural non-stick coating, meaning it won't stick to your baked goods like foil sometimes can. You won't have to grease it first, either. Your cookies will slide right off the parchment paper and onto your cooling rack without an ounce of effort.
So if you love crispy, brown-bottomed cookies, by all means, keep reaching for the aluminum foil. But if you're on a quest to bake the perfect batch of chocolate chip cookies (or any other cookie variety you like), it's time you listened to science: Ditch the aluminum foil, and instead make parchment paper your new cookie baking secret weapon.