Which side of the foil to wrap the food in when baking

What reflects the shiny surface of the foil

The explanation about reflection looks plausible: from the school physics course, we remember this property of shiny surfaces. But what do they reflect when cooking in the oven?

There are three ways to transfer heat: conduction, convection, and thermal radiation. When cooking in the oven, the last two are decisive, since neither the baking sheet nor the foil comes into direct contact with the heating elements.

Convection

In the oven, heat is transferred to the product from the heating elements through the movement of air. There is convection in any oven, not only in the one that has this word in its name. If we are talking about a convection oven, we mean a fan that moves the heated air faster.

A shiny (or matte) surface does not affect convection. The foil will heat up, no matter which side it comes into contact with the product, and transfer this heat.

More important here is how tightly the foil is wrapped around the contents. If air is left between the product and the aluminum sheet, it can become an insulating barrier and slow down the transfer of heat.

Heat radiation

Convection is most important in oven cooking, but radiation is responsible for some of the heat transfer. It is emitted by any object with a temperature above absolute zero (-273, 15 ° C), that is, all elements of the oven and all its contents.

For infrared radiation, the side of the foil will matter: the shiny surface reflects the rays, the matte surface catches. But this difference in heat transfer is only important for highly sensitive instruments. The side of the foil will have little effect on the speed of cooking dinner.

Why foil has different sides

Different surfaces of the foil are not made on purpose, this is a feature of the technological process. Aluminum is rolled into thin sheets of foil with heavy metal rollers, like dough with a rolling pin. One side is in contact with the rollers, which polish it to a shine. The other remains matte.

Which side of the foil should contact the food

Experts believe that in this matter you can completely rely on your taste, since there are no functional differences. Robert Wolke writes about this in his book What Einstein Told His Chef. Reynold's Kitchen experts came to a similar conclusion.

The question of which side to use the foil is important only for aluminum sheets with a non-stick coating. In this case, the manufacturer recommends placing the products on the matte side marked non-stick.