How is glass made?

Ordinary glass starts mainly with silica sand, which is melted at extremely high temperatures — around 1,700°C. To lower the melting point and make the process practical, manufacturers add soda ash (sodium carbonate) and limestone (calcium carbonate). Once molten, the mixture can be shaped by blowing, pressing, or floating it on a bed of molten tin to make perfectly flat sheets — the modern “float glass” process. Crucially, the liquid is cooled quickly enough that its atoms freeze in a disordered, non-crystalline arrangement, which is why glass is transparent and brittle. Adding different minerals produces colors and special properties, and glass can be recycled endlessly.