Foil, as you’ll find it in any kitchen drawer, is made of aluminum. Specifically, it’s made from commercially pure aluminum, typically 99% or higher purity, with trace amounts of iron and silicon as the main impurities. Despite the fact that many people still call it “tin foil,” actual tin hasn’t been used to make kitchen foil since the early twentieth century.
The Aluminum in Your Kitchen Foil
Household aluminum foil belongs to a category of aluminum known as the 1xxx series, which refers to unalloyed, nearly pure aluminum. The most common grades used for foil contain at least 99% aluminum by weight. Iron is the most common impurity, and silicon is the second most common, present at levels between 0.01% and 0.15%. These aren’t intentional additions for strength or performance. They’re simply trace elements left over from the smelting process that are too costly to remove completely.
This high purity is what makes aluminum foil so useful. Pure aluminum is extremely malleable, meaning it can be pressed into incredibly thin sheets without cracking or tearing. It’s also lightweight, resistant to corrosion, and a good barrier against moisture, light, and oxygen.
How Thin It Actually Is
Standard kitchen foil is remarkably thin, typically between 10 and 18 microns (0.01 to 0.018 millimeters). For perspective, a human hair is about 70 microns thick, so regular foil is roughly one-quarter the width of a single strand of hair. Heavy-duty foil runs between 18 and 24 microns, and extra-heavy-duty foil, the kind used for grilling or wrapping large cuts of meat, can reach about 40 microns.
To get aluminum that thin, manufacturers pass aluminum sheets through polished steel rollers repeatedly, compressing the metal thinner with each pass. During the final rolling stage, two sheets of foil are stacked together and rolled simultaneously. This is why your foil has one shiny side and one dull side. The shiny side was pressed against the polished steel roller. The dull side was pressed against the other sheet of foil. Despite persistent kitchen lore about which side to use, both sides perform identically for cooking, freezing, and food storage. The difference in heat reflectivity between them is negligible. Reynolds, the largest foil brand in the U.S., confirms it doesn’t matter which side faces your food.
Why It Replaced Tin Foil
Before aluminum foil became standard, tin foil was the go-to wrapping material. The first aluminum foil rolling plant opened in 1910 in Emmishofen, Switzerland, and aluminum gradually replaced tin over the following decades, fully taking over by the mid-twentieth century. The reasons were practical: aluminum is far more malleable than tin, making it easier to wrap tightly around food, and tin left a noticeable metallic taste on anything it touched. Aluminum doesn’t. The phrase “tin foil” stuck around long after the actual tin disappeared, which is why so many people still use the term today.
Aluminum Leaching Into Food
Aluminum foil can transfer small amounts of aluminum into food during cooking, particularly under certain conditions. The key factors are acidity, salt, and heat. A study published in Food Science & Nutrition found that marinated fish (salmon and mackerel prepared with acidic and salty marinades) showed aluminum levels up to 20 times higher after being wrapped in foil and baked at 220°C for 40 minutes, compared to unmarinated samples. Even without marinade, baking fish in foil still increased aluminum content, just to a much smaller degree.
Acidic foods like tomatoes, citrus-based sauces, and vinegar-heavy marinades accelerate this transfer because low pH breaks down the thin oxide layer that naturally forms on aluminum’s surface. Salt has a similar effect. Plain, dry foods wrapped in foil pick up very little aluminum by comparison.
Aluminum foil melts at about 660°C (1,220°F), well above any home oven temperature, so melting isn’t a concern. But if you regularly cook acidic or heavily salted foods in foil, you may want to use a layer of parchment paper between the food and the foil as a barrier.
Non-Stick and Specialty Foils
Non-stick aluminum foil is the same base metal with a food-safe coating on one side. That coating is typically silicone-based, using a blend of silicone resins and release agents that prevent food from bonding to the surface during cooking. Unlike regular foil, non-stick foil does have a designated food side, usually labeled on the packaging. The coating also creates a barrier that reduces direct contact between the aluminum and your food.
Recycling and Environmental Cost
Producing aluminum from raw ore (bauxite) is energy-intensive, requiring about 66 megajoules per kilogram. Recycling aluminum, on the other hand, uses roughly 95% less energy because the metal has already been refined to its elemental form. Solid-state recycling methods can recover aluminum using as little as 1 megajoule per kilogram. Aluminum foil is recyclable in most municipal programs, though it needs to be relatively clean. A sheet caked with baked-on food or grease typically gets sorted out as contamination, so a quick rinse before tossing it in the bin makes the difference between it being recycled and landfilled.
How Aluminum Compares to Other Metal Foils
Aluminum isn’t the only metal sold in foil form, but it’s by far the most common for household use. Copper foil is used in electronics and crafts. Gold leaf, used in decorating and high-end cuisine, is technically a foil but on a completely different scale: a single sheet of 23.75-karat gold leaf measures only about 120 nanometers thick, roughly 100 times thinner than standard aluminum foil. Tin foil still exists but is now a specialty product, not something you’d find in a grocery store. For everyday cooking, wrapping, and food storage, aluminum’s combination of low cost, flexibility, and food safety keeps it as the default.