MUNDANE MYSTERIES: Why Is One Side of Tin Foil Shiny?

In the wake of Thanksgiving, you more than likely utilized tinfoil to cover some, if not all, of your leftovers. Have you ever noticed, though, that tinfoil has 2 different-looking sides, one shiny & one dull? Why is that?

The fact that tinfoil has 2 sides with different appearances is mostly the result of the manufacturing process. To create aluminum foil, a huge slab of aluminum is fed through heated steel rollers until it’s a mere 5 millimeters thick. Then, it’s moved to a set of cold rollers to be thinned even further. And, since it’s thin enough to break at that point, manufacturers push through 2 sheets at a time. When the top of the top sheet & the bottom of the bottom sheet brush against the rollers, they get shiny. But, since the bottom of the top sheet and the top of the bottom sheet only touch each other, they stay dull.

Since the shiny side seems more reflective, a lot of people think that side should face up while cooking or baking. And, if you were trying to fry an egg outside on a hot day, that would make sense, since more sunlight would reflect off the shiny surface, transferring more heat to the egg. But, most regular ovens heat food through convection, where the air in the oven circulates heat energy from the hot coil elements to the food. In other words, convection ovens don’t care how reflective the tinfoil is.

With that said, shiny-versus-dull does matter when it comes to certain specialized types of aluminum foil. For example, the dull/non-shiny side of Reynolds Non-Stick Aluminum Foil has a coating that helps keep food from sticking to it, so you should definitely place your food on that side.

Aluminum foil also isn’t just for ovens. From sharpening scissors to scrubbing grills, it has tons of other uses & none of them depend on whether you use the shiny or the dull side…the tinfoil company just wants you to keep using it!

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