How do you fuse glass?

Glass is made from melting silica or sand (Silicon Dioxide DiO2) at extremely high temperatures. SiO2 in its crystalline form is known as quartz.

The main ingredient in glass is therefore quartz (as washed sand) mixed with a little sodium oxide Na2O and calcium oxide (CaO) or quicklime. These ingredients are mixed together and placed in a furnace until they all form a melt. The melt is glass.

Other additives can be added to the mix to make specialized glasses.