You can’t see it, but there’s a polymer coating inside your aluminum can. 🥫 @Phillip Cook uses chemistry to prove it! Working with lye, which is highly caustic and requires proper safety equipment (so please don't try this one at home), he makes a solution that reacts with the aluminum, converting it into a compound that dissolves in water. When the aluminum is gone, you can see the polymer coating! These coatings are useful because without them, acidic drinks could slowly corrode the aluminum