Unless you are using foil that's labeled non-stick, which does have a non-stick side, it does not matter what side you use. Both the shiny and dull sides can be used the same way to cook, freeze, and store food.
Food wrapped in foil for the oven should be wrapped with the dull side around the food, it collect the heat. The shiny side reflects it and should be on the outside / facing down if the food is laying on a tray.
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.
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. For Reynolds Wrap® Non-Stick Aluminum Foil, you'll want to have the dull side facing up.
Does the Shiny Side of Aluminum Foil Reflect More Heat? Aluminum foil reflects heat from both its dull and shiny sides equally. While aluminum foil has a dull and shiny side, there is no difference in how either side reflects heat.
According to the U.S. Department of Agriculture, aluminum foil's two-sided finish is the result of its production process. When the material passes through rollers, two layers of foil are pressed at the same time, which reduces the risk of breakage. As a result, one side is shiny and the other is matte.
So, any time you use a single side foil insulation, the foil needs to be facing toward the living space. So in a loft the foil faces downward.
Cover Dishes Properly: Ensure that aluminum foil covers the entire dish but does not touch the oven walls or heating elements. This helps prevent electrical issues or fire hazards. Avoid Full Rack Coverage: Completely covering an oven rack with aluminum foil can block airflow and cause uneven cooking.
I agree with previous answer as the shiny and not shiny part has the same heat conductivity and it does not mean one side had been oxidized more than the other. The difference in shininess is simply a result of manufacturing process.
Tin foil is stiffer than aluminum foil. It tends to give a slight tin taste to food wrapped in it, which is a major reason it has largely been replaced by aluminum and other materials for wrapping food.
Lining your oven with foil will actually increase the intensity of heat that will result in surface damage and even go as far as preventing even cooking. So leave it out, invest in an oven-safe cleaning cloth, and enjoy your golden brown cookies, holiday ham, and more!”
A: The matte side is where you would apply the color or lightener. The shiny side always faces out, to help warm up the foils.
The Risk Of Bacteria Growth
The Centers for Disease Control (CDC) warns that the presence of air can help potentially dangerous bacteria such as staphylococcus (staph) and Bacillus cereus, which can thrive in the conditions created by tinfoil storage, grow faster.
Aluminum foil's natural non-stick surface aids in easy cookie removal. Monitor baking time closely as cookies may cook faster on foil. Adjust oven temperature down by 10-15 degrees Fahrenheit to prevent overbrowning. Lightly grease foil or use non-stick spray to prevent cookies from sticking.
Using aluminum foil to keep your oven clean may be tempting, but lining an oven with foil increases the intensity of heat on oven surfaces, which can lead to surface damage like scratching or chipping on the porcelain finish and damage to heating elements. It can also prevent even cooking.
Be sure to poke holes throughout the foil to allow for proper airflow.
Covered baking typically requires a longer cooking time due to the slower heat transfer.
Regular foil does not have a non-stick side. You have to grease it with cooking spray, butter, or oil to get a non-stick surface. You can buy non-stick foil that has one side sprayed with a food-safe non-stick coating. Typically, it's the dull side and sometimes it is labeled as non-stick so that it's easy to tell.
An air space must exist on a minimum of one side of the product (always on the reflective side (residential attic – preferably oriented facing down)). Radiant barriers by definition do not require an enclosed air space to provide benefit. This application (radiant barrier) is typically installed in a ventilated attic.
While some advocate for aluminum foil balls, asserting they can deionize tank water to prevent clogs and maintain cleanliness, there's limited scientific backing for this claim. Fortunately, there are numerous proven and safe alternatives for toilet maintenance.