Is the Dark Brown Buildup on Your Baking Sheets Safe? An Expert Weighs In

I’ve worked in kitchens nearly all of my life and I can tell you that some of the most unexpected equipment is the most prized. As a prep cook in a pizza restaurant in my teens, I was disgusted by the giant, mostly-blackened stainless steel pot that the chef used to prepare marinara sauce. To me it looked like it belonged in the trash, but it was his pride and joy.

Only years later would I understand why he loved it so much. That pot, thanks to thousands of uses, had developed a rich patina that my chef treasured and cherished. Now I, too, treasure and cherish that naturally-created non-stick surface, but since there’s so much misunderstanding about it, I wanted to clear the air about its purpose and whether it is safe, so I contacted an expert to provide some clarity.

Patina, Explained by an Expert

What exactly is the dark stuff that builds up on your baking sheets and how does it get there? According to Lisa McManus, executive editor of ATK Reviews, patina is a coating that forms during a chemical process that happens when you frequently use your baking sheet to cook foods in oil.

“The oil polymerizes on the surface [of the baking sheet], like the seasoning on a cast-iron or carbon-steel pan,” says McManus. “Polymerization means as the oil heats, its molecules link up and bond together and to the pan’s surface, forming a naturally non-stick layer that darkens in the heat of the oven.” Repeated use improves the patina, and, thankfully, according to McManus, “it’s completely safe and normal.” Whew!

The Benefits of Patina

The patina that forms on your baking sheet provides a naturally nonstick surface, unlike commercially made nonstick kitchen tools, which often use chemicals to create a similar effect. This protective layer makes it easier to do your cooking and cleaning. Thanks to its dark color, which heats up faster and browns food more quickly than light-colored surfaces, patina also helps cook food faster, says McManus.

To prove it, she tested “shiny new sheet pans” against “dull, browned, older sheet pans” in the test kitchen. Using temperature trackers, she was able to confirm that “the older browner sheets heated faster, hitting just over 400 degrees in 15 minutes, whereas the shiny new sheets only reached 350 degrees in the same amount of time.”

How To Clean and Store Your Baking Sheets

You might be tempted to put your dirty baking sheet in the dishwasher, but McManus recommends hand-washing. Because most pans are made of aluminum, she says, they’re prone to darkening in the acidic environment of the dishwasher. While harmless, that darkening can affect the appearance of your baking sheet.

To keep it looking its best, use regular dish soap with hot water and a sponge. If, for some reason, you want to remove the patina, McManus suggests using Bar Keeper’s Friend, an abrasive kitchen cleaner. 

As for storage, McManus likes to keep her baking sheets upright on their edges “because they take up less space, and I can grab them like a book off a shelf.” If that’s not an option, she says, stack them and store them flat on the refrigerator.

However, she advises, “Don’t put them too far away—you’ll want to use them often!” As for her favorite baking sheet, she recommends the Nordic Ware Baker’s Half Sheet. “It bakes and roasts food beautifully and is affordable, lightweight, and easy to handle. To maximize its use, we recommend getting a wire rack and a lid for it.”