Glass was first discovered in the area around Persia in 3500 - 3000 BC, and it is the substance you get when you mix quartz or silica, potash and chalk at high temperatures.
In the beginning of glass blowing history, a basic glass cup was made by rolling an iron bar into a mix of horse dung and clay to create a mould. You would then wait for the mould to dry. Once the mould was dry, you would dip it into the molten glass. When the glass was cold you could scrape out the horse dung/clay mix and you would have a cup or perfume bottle.
Today most glass is mass-produced on big machines. Window glass is made by putting an iron bar vertically into the molten glass and then lifting it up to a height of about 20 metres or more. After that it is cut into suitably sized pieces.
However, in most countries you can still see sweating people making glass with a blowpipe the way the Romans did around 30 BC.
Blowing glass is a lot more difficult than it appears and shouldn't be tried at home. However, if you've ever wondered how glass is blown, here's how...
Take a hollow piece of steel and rotate it in the molten glass until you have gathered the amount of glass that you need.
Go to your glass bench, or your glass stand if you are from Eastern Europe.
When you have the right shape (or the best you can do) you transfer the piece to a punty, which is a steel rod with some hot glass in the end which you use as a glue.
With the piece on the punty, you warm it up in the furnace and using the same tools as before, you can finish the piece to your heart's desire.
To avoid having the glass crack or explode, you have to cool the glass very slowly in the annealing oven1. After about 12 hours you can touch the piece.