Should You Use the Shiny or Dull Side of Foil? Reynolds Settles the Debate

We use it to wrap ribs on the grill, cover a casserole before baking in the oven and as a pan liner when roasting a whole chicken or pork loin. Aluminum foil is one of the kitchen’s most common and versatile products. It is so commonplace, however, that perhaps we take it for granted and don’t think twice about whether to cook on the shiny or dull side, if it’s safe to place under the broiler or if it’s effective against freezer burn. 

To get a thorough understanding of all things aluminum foil, we turned to the experts at Reynolds and to Abbey Thiel, Ph.D., a food scientist and the expert behind the blog and YouTube channel Abbey the Food Scientist. As it turns out, there is actually a difference between the shiny and dull sides of foil, but that difference may not be exactly what you are thinking.

“The difference is purely a result of how aluminum foil is manufactured, not because the sides have distinct properties,” Thiel said. “During the production process, aluminum is filled into thin sheets through a process called milling. To make the foil thin enough without tearing, two sheets of aluminum are rolled at the same time. The side of the foil that touches another sheet during milling ends up dull because it doesn’t get polished by the rollers. The other side, which is in direct contact with the rollers, becomes shiny.” 

Which Side of Aluminum Foil Should You Use?

If the shiny and dull sides of aluminum foil are strictly a result of whether the foil was against a roller, does it really matter which side you use? The straightforward answer here is that no, it doesn’t really matter which side—shiny or dull—you use when cooking.

“The reason for this is that aluminum foil works primarily through conduction, which is the process of heat transferring through direct contact,” Thiel said. “The foil’s main job is to conduct heat from the oven, grill or stovetop to the food, and both sides of the foil do this equally well.”

According to Reynolds, which has been making aluminum foil for more than 75 years, both sides are OK to cook on. “With standard and heavy-duty foil, 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,” Reynolds indicates on its website.

The shiny side of aluminum foil does reflect a small amount of heat radiation; however, this effect is so minimal that it doesn’t affect how the food cooks, Thiel said. “The thermal conductivity of aluminum, which is its ability to transfer heat, is not a surface property—it’s a characteristic of the material itself. That means that both the shiny and dull sides of the foil have the same ability to transfer heat into your food.”

What About Nonstick Foil?

Because nonstick foil is specifically created to have a nonstick side, it does matter which side you use. According to Reynolds’ website, “For Reynolds Wrap Non-Stick Aluminum Foil, you’ll want to have the dull side facing up. A tip is that if you can read the writing on the foil then you have the right side up to get all the benefits of non-stick foil.” 

Common Foil Uses

Perhaps you turn a piece of aluminum foil into a pouch and add vegetables or chopped potatoes, garlic, herbs and oil and then place it on your grill for a simple side dish. Or maybe you like to line your baking sheet with foil when roasting portions of salmon. These are both great uses of aluminum foil, and they demonstrate the variety of ways it can be used. 

When you line a pan for baking or roasting, you are not only making cleanup easier and helping to prevent sticking, but you are actually shielding the food from some of the direct heat, Thiel explains. But when you cover a dish for baking, like when making a lasagna or another casserole, you are actually trapping steam for moisture retention, preventing splatter and even shielding the food from excess browning (think covering the edges of a pie crust or the breast meat on a roast turkey). Similarly, when grilling you can use foil to protect delicate food like fish, wrap proteins that benefit from extra moisture (like ribs or pork shoulder) or shield food from potential flare-ups.

Safety Tips

In nearly all cases, aluminum foil is safe to use. It is one of the most effective products in preventing loss of moisture and vapor, making it ideal for long-term storage in the freezer. When it comes to roasting, it can be safer to use than parchment paper, which is only oven-safe to about 420°F and not ideal for direct heat, according to Reynolds. Aluminum foil can be used under the broiler and directly on the grill grates. 

One important safety tip, however, is to be careful around acidic or salty foods like tomato sauces or vinegar-based marinades for meat. Thiel explained that a small amount of aluminum can actually leach into the food if it comes into contact with too much acid or salt. 

“This is because acids and salts can corrode the aluminum surface. While this amount is considered minimal and safe by health authorities, people with conditions like kidney issues may want to limit aluminum exposure as their bodies have difficulty excreting it,” Thiel said.

The Bottom Line

When using standard or heavy-duty foil, you can use either side, shiny or dull. The difference in appearance is due to the manufacturing process and doesn’t affect how you use the foil. If you are using nonstick foil, be sure to have the dull side facing up to get the nonstick benefits.