Would it matter if you use the matte side or shiny side of aluminum foil toward food?

Answer 1

Take it from the people at Reynolds. They make the stuff. They will tell you that it makes no difference which side is in or out.

According to the description on the TV show "Modern Marvels", two "sheets" of aluminum are pulled through the pressing machine and rollers at the same time. The "sheet" started off as a solid block, but as it is pulled through rollers, the "sheet" becomes longer and narrower (several miles long). As the two thinner sheets are pulled along together, the outside of both sheets (one on the bottom, one on the top) are exposed more and longer to heat and to the lubricant coolant liquid that Reynolds sprays on the product as it goes through the rollers. The opposite side of each sheet, unexposed, takes a "matte" or un-shiny appearance. They then take the top sheet to one set of rollers above, the bottom sheet to a roller below and "separate" the 2 sheets from each other and make them into 2 rolls. The two rolls are then sent to the processing/packing plant where they are separately cut into the standard length and width and boxed for sale.

The Reynolds Company states that for cooking or freezing, it makes no difference whether the matte side or the shiny side is out. Optical light scatters differently from the dull side than from the shiny side, which is more like a mirror. But both sides absorb or reflect light (and infrared radiation) equally.

The myth that the shiny side must be out started shortly after the product was first manufactured, according to Reynolds.

Psychologically, the myth may have more to do with human attraction to all things shiny.

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The shiny side should go on the inside. Here's why:

The shiny side is shiny because it is more reflective of light. While light reflectivity doesn't necessarily tell you how well something can reflect things like gamma rays, light and heat are relatively close on the electro-magnetic spectrum, so you can generally assume that heat and light will be reflected in the same way by a certain material.

In the case of cooking foil, if you put the less-reflective side outward, it will absorb more heat than the shiny side would have. Additionally, the shiny side will help heat build up under the foil.

A similar example can be found in the reflective silver safety blankets found in first aid kits. While both sides are reflective, the warming property comes from body heat reflecting inside the blanket. The outside shininess might help with visibility in emergencies, but doesn't help you get warmer.

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Your answer is incorrect acording to Reynolds Co.

I called them last year with this same question and was told that using either side of the foil will yield the exact same results. The only reason for a shinny side and a dull side is because of the way that the manufacturing process works and that is it.

Answer 2

Both sides of aluminum foil are essentially the same, so it doesn't make a significant difference which side is facing inwards when wrapping food. It is more important to ensure that the food is properly wrapped and sealed to retain moisture and prevent leaks.