Which side of the aluminum foil should touch the food?

My kitchen is never without aluminum foil. From covering bread that's browning too quickly as it bakes to scrubbing dirty pans with a ball of it to leak-proofing my favorite cheesecake in a water bath, foil is a cooking essential. And since foil is sturdy and easily cleaned, instead of tossing it after one use, I reuse it for baking, cleaning, and storing food.

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Recently I saw the viral reel (below) that says, "Did you know that the shiny side of foil is for hot food and matte side is for cold?" It also claims that the dull side of foil is non-stick. Have I been using foil wrong all these years? Here's what I found out from the experts.

Why Does Foil Have a Shiny Side and a Dull Side?

The reason foil has a shiny and dull side is due to how it's made, a process called milling. According to the U.S. Department of Agriculture (USDA), two layers of foil are placed on top of each other and squeezed through polished steel rollers to flatten and shape the foil. The two layers are then separated for packaging and distribution.

The side that was in contact with the polished steel rollers is shiny. The other side, where the two layers of foil touch each other, comes out dull. Essentially, one side got buffed more and became shiny.

Which Side Is Best To Use?

Reynolds, a popular brand of foil, states on its website that "it's perfectly fine to place your food on either side so you can decide if you prefer to have the shiny or dull side facing out."

Chemist and former food writer for the Washington Post, Robert L. Wolke also wrote in What Einstein Told His Cook that it makes no difference which side of the foil you use. Both claim that the difference between the sides is purely a result of how foil is manufactured.

However, neither explains why it doesn't make a difference.

Over the years, I've noticed food experts reason that the shiny surface is more reflective, bouncing off heat waves, while the dull side will trap heat. And this determines which side should be used.

For example, renowned baker and cookbook author Alice Meldrich recommends baking cookies on a sheet pan lined with foil dull-side up, because it retains more heat in the oven, yielding cookies with a crispier and more golden brown bottom.

Though there is a difference in how much heat the shiny vs. dull side reflects or retains, measured over time and considering the type of heat the oven emits, that difference is negligible and has little to no discernable impact on the food. That's why it doesn't matter which side you use. This is true whether the food is hot or cold.

This Type of Foil Does Have a Non-Stick Side

Regular foil does not have a non-stick side. You have to grease it with cooking spray, butter, or oil to get a non-stick surface.

You can buy non-stick foil that has one side sprayed with a food-safe non-stick coating. Typically, it's the dull side and sometimes it is labeled as non-stick so that it's easy to tell.

The Takeaway

Foil has a shiny side and a dull side because of how it is manufactured. Unless you are using foil that's labeled non-stick, which does have a non-stick side, it does not matter what side you use. Both the shiny and dull sides can be used the same way to cook, freeze, and store food.

Aluminum foil is an indispensable item in nearly every household. It's versatile: You can use it for everything from foil packet recipes to cleaning your grill. The handy product comes equipped with a bit of a mystery, too. One side of a sheet of aluminum foil is shiny, and the other side is dull and flat. You won't find any information about the reason for the difference if you check the rectangular box it's sold in either. So what gives?

Is it best to position aluminum foil with the shiny side up or down before you put that casserole in the oven? Before you tear off another sheet, here's what you need to know.

Why Is Aluminum Foil Shiny on One Side?

When you pull a sheet of aluminum foil off the roll, there's a notable difference between the two sides. One is so shiny that you can practically use it as a mirror. The other, well, it's still silver but not nearly as sparkly. It turns out there's a good reason.

According to Reynolds Wrap, the difference is a byproduct of the manufacturing process. You see, aluminum foil is milled in different layers. Heat and tension are applied to stretch the foil until it's thin enough to become the familiar sheets you buy in stores and use at home.

The factory manufactures two sheets of foil simultaneously to ensure the sheets are strong enough to withstand breakage. The side where the foil comes into contact with another layer of foil appears dull, while the other side, which hasn't made contact with another sheet, appears shiny. In other words, the two sides look different, but when it comes down to it, they're both made of the same stuff.

Does the Shiny Side of Aluminum Foil Reflect More Heat?

Aluminum foil reflects heat from both its dull and shiny sides equally. While aluminum foil has a dull and shiny side, there is no difference in how either side reflects heat.

Should You Use Aluminum Foil with the Shiny Side Up or Down?

Quite simply, it doesn't matter what side of aluminum foil you use. Either is acceptable. Since the exact same material makes up both sides, they will perform precisely the same way. The only difference is aesthetic. So feel free to work both ways. In the end, your food will cook the same. Mystery solved.

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