The Right Way to Use Aluminum Foil in the Kitchen, According to Experts

We're answering your most pressing questions: Is it safe to use foil in the microwave or air fryer? And should the shiny side be up or down?

Aluminum foil might very well be one of the most versatile supplies in your kitchen. Not only can it be molded into any shape or crevice, but it can also be transformed into a liner, pouch, tent, or wrapper. Additionally, the shiny material is extremely durable, especially when compared to wrappings such as parchment paper.

But despite the versatility of aluminum foil, there are many misconceptions about using it for home cooking. So, to understand how to best use aluminum foil in the kitchen, we turned to a few food experts. Learn the difference between regular vs. heavy-duty foil, plus whether or not you can use aluminum foil in the oven, air fryer, or microwave. And of course, we answer everyone's most pressing question: Shiny side up or down?

Functions of Aluminum Foil

Aluminum foil, sometimes called tin foil, is a very thin shiny sheet of the metal aluminum. It's made by rolling large slabs of aluminum until they are less than 0.2 millimeters thick.

The purpose of aluminum foil depends on the application, but often, it's used as a packaging or cover in cooking, says Ali Manning, food scientist and founder of Umami Food Consulting. That's because aluminum foil is an excellent conductor of heat, so it can prevent heat and moisture escaping from food (which will ensure a delicious meal), according to Stephen Chavez, chef instructor at the Institute of Culinary Education. Aluminum foil is also used to line the bottom of baking pans during cooking, preventing food from sticking and making cleanup a breeze, says Chavez.

foil on sheet pan with roasted veggies
LauriPatterson / GETTY IMAGES

Regular vs. Heavy-Duty Foil

As the name suggests, heavy-duty foil is thicker and sturdier than regular foil, says Manning. This extra level of durability can withstand high heat, making it appropriate for wrapping food and placing it directly on coals or an open fire, according to Chavez. Regular foil is thinner, so it retains heat and moisture to a lesser extent. This makes it ideal for more basic applications, like covering cooked foods to keep them warm and juicy, says Chavez.

Should You Use the Shiny or Dull Side of Aluminum Foil?

According to the U.S. Department of Agriculture, aluminum foil's two-sided finish is the result of its production process. When the material passes through rollers, two layers of foil are pressed at the same time, which reduces the risk of breakage. As a result, one side is shiny and the other is matte.

However, the different finishes do not have different functions, and they react with food in the same way. People often ask which side of aluminum foil is nonstick. The answer is that it doesn't matter which side faces up or down when you're cooking with traditional aluminum foil—but if you're working with a specific nonstick variety, which has a protective coating, be sure to use the side recommended by the manufacturer.

Using Aluminum Foil in Ovens, Air Fryers, and Microwaves

"Aluminum foil can absolutely be used in a regular conventional oven, as well as an air fryer, which is just a mini convection oven," explains Chavez. "Foil will conduct heat perfectly in both and will keep the insides of your [appliances] clean."


You might be surprised that aluminum foil can be used in microwaves to prevent overcooking, though certain safety measures must be in place. According to the USDA, no more than a quarter of the food should be covered in foil, which should be new and smooth (i.e., free of wrinkles). Otherwise, the wrinkles can cause electrical arcs, or sparks, which are essentially mini lightning bolts that can damage your microwave oven, says Chavez. The foil should also be shaped around the food and placed away from the microwave walls, at least 1 inch or farther, according to the USDA.

Additionally, if your microwave has metal parts, extra care should be taken to ensure the foil doesn't touch the metal components. The USDA also advises keeping small pieces of foil away from the metal parts. When in doubt, check your appliance's manual for safety precautions, and follow them exactly. If doing so feels like too much of a hassle, you may want to consider other cooking methods or coverings for the microwave.

Avoid Aluminum Foil When Cooking High-Salt or High-Acid Foods

Regardless of the cooking method you use, it's crucial to ensure aluminum foil doesn't come into contact with high-salt or high-acid foods, like tomato sauce, citrus, or vinegar, says Chavez. These ingredients will cause an unfavorable reaction with the aluminum foil, causing off-notes in the finished product, notes Manning. High-salt and high-acid foods can also cause aluminum to leach into the food, posing a potential health risk.

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