Borosilicate Glass

Borosilicate glass, often just referred to as 'boro' or 'hard glass', has a COE of 33. This glass needs a higher temperature to melt and is generallly stiffer when molten than glass with a higher COE. Many borosilicate glass colours are reactive and can change dramatically depending on flame atmosphere. Some borosilicate colours, for example, amber/purple colours, can also change depending on light source.