Floating glass. The 90% of the flat glass produced in the world, called float glass, is made through the floating system invented by Alastair Pilkington, where the melted glass is poured on an extremity of a melted tin bath. Today this operation is carried out in controlled atmosphere. Glass floats on the tin and expands along the bath surface, forming a flat surface on both sides. Glass cools off and solidifies while is running along the bath, creating an uninterrupted ribbon. The product is then burnished and gets hot again on both sides, that's why it's going to have two perfectly parallel surfaces.