It doesn’t matter.

Have you every wrapped a succulent half chicken in aluminium foil before placing it in the oven and wondered whether you should put the shiny side in (touching the food) or out (facing the oven)? Does the shiny side reflect more heat, resulting in a crispier finish? Or maybe the dull side is a better conductor, creating a more even cooking surface?

According to Reynolds, a major producer of aluminium foil, it doesn’t matter which side you use.

The foil is ‘milled’ in layers during production. Milling is a process whereby heat and tension is applied to stretch the foil to the desired thickness.

Manufacturers mill two layers in contact with each other at the same time because if they don’t, the foil would break during the milling process.

Where the foil is in contact with another layer, that’s the ‘dull’ side. The ‘shiny’ side is the side milled without being in contact with another sheet of metal.

The side coming in contact with the mill’s highly- polished steel rollers becomes shiny. The performance of the foil is the same, whichever side you use.

But, if you are using non-stick foil, there is a difference between the two sides because the non-stick coating is only applied to one side.  In this case, the non-stick side is usually labelled as such by the manufacturer.