Aluminum foil contains only a little bit of impurities, Fe, or iron, which is highly reactive with aluminum, and it can also contain very little Mg magnesium or other elements. These elements form aluminum and intermetallic compounds, or are dissolved in aluminum, so they don't melt easily when heated, and they don't release environmental hormones like plastic containers. Sometimes aluminum foil discolors, but this is due to organic matter from food, and generally pure aluminum contains a little bit of 660 degrees iron But you can use it up to 650 degrees without worrying. -Aluminum reacts with oxygen in itself so much that contact with air forms a thin film of aluminum oxide on the surface. Therefore, it is rare for aluminum to melt into food even if it comes into contact with food, so you can use it with confidence.