Glass is one of the most truly amazing materials that is on this planet. It is also one of the weirdest. Glass comes from sand. However, sand is not see-through so how does it become glass? It’s because glass is both a solid and liquid at the same time. It’s a bit like Ice. Ice is a solid, in other words you can pick it up and carry it, but it is also a liquid because if you do carry it around it will melt.
If you superheat sand it melts into this molten form of super hot super gloopy material that you can pretty much shape into whatever you want. In modern times we use moulds to make glass into practical shapes that we want such as windows. Tewkesbury Double Glazing company Firmfix knows all about this kind of thing for their double glazed windows.
In the past glass was shaped by blowing into it. Not that people put their lips up to the stuff, it was too hot. Instead they would insert rods into the hot sand and blow air inside. They were able to shape glasses and bowls in this way for centuries, simply cutting off the excess with a pair of iron scissors. When the glass cooled it was perfectly clear.
The reason why glass is also a liquid is that it is actually still moving when you hold it! The atoms are moving at an incredibly slow rate, almost to the point of being static but they are moving and this is why the sand is clear.