The Art of Melting Sand

A look at the chemistry of glassmaking

In its most basic form, glass is just melted silicon dioxide (SiO₂) sand, also known as a silica or quartz. You need, 1700 °C to melt silicon dioxide, which is quite a lot. A campfire cannot reach that temperature, but you could do it in a kiln (ancient brick oven). You can get glass made from pure silicon dioxide today, but it is expensive due to the high temperatures required to make it.

A kiln is just a brick oven. They give you high temperatures usable to melt glass.

Humans learned over time that by adding in sodium carbonate (Na₂CO₃) or potassium carbonate (K₂CO₃) and calcium oxide (CaO) they could make the mixture melt at 580 °C and get more durable glass. It is the sodium (Na) which when heated reacts with silicon dioxide to create shorter chained silicon dioxide crystals.

In general, longer chains require higher temperature to melt. You can see the same when looking at hydrocarbons. Hydrocarbons are chains of carbon atoms with hydrogen attached. Very short chained hydrocarbons are gasses, longer ones are liquids (oils) while the longest ones are solid. A solid hydrocarbon is what we call a polymer or a plastic.