Most glass today is made by melting sand containing silica and other chemicals into a liquid at very high temperatures, and then cooling the liquid until it becomes hard.

Glass is a very durable building material – some 12th century glass still survives in windows today. But most importantly, glass is one of the only materials that allows light into a building. Using natural rather than artificial light is an excellent way to save energy in a building and helps create beautiful, airy spaces.