What characterizes float glass?

Float glass is primarily characterized by its manufacturing method, which involves floating molten glass on a bed of liquid tin. This unique production process allows for the creation of flat, uniform sheets of glass with excellent optical clarity and smooth surfaces. The molten glass spreads evenly on the tin, leading to a continuous sheet that is later cooled and cut to size.

The floating of glass on tin contributes to the glass's mechanical properties and its visual quality; it avoids the distortions that can occur with other glass-making processes. This is why option B is the correct answer.

The other options do not accurately describe float glass. Volcanic glass refers to naturally occurring glass formed from lava, which is unrelated to the industrially produced float glass. A foamy texture describes materials with air bubbles or a porous structure, which does not apply to the smooth, flat surface of float glass. Lastly, while glass can be reinforced with metal through processes like laminating or using metal grids, standard float glass itself is not inherently reinforced with metal, making those options incorrect as well.