I love hard glass! Ok, so all glass is hard right? Wrong. There is also soft glass. Glass is made from silica and although melting pure silica is possible, it requires extremely high temperatures. To overcome this, additional chemicals called “fluxes” are added to the silica to lower the melting temperature, and change the working characteristics. “Hard glass” is usually used in reference to borosilicate glass – or ‘Pyrex’. The primary fluxing agent is Boron Oxide. Boro has a COE (coefficient of Expansion – more about that another time) of around 33, and is a good glass for making sculptural objects. Boro requires more heat in order to work it than soft glass. “Soft glass” refers to the many brands of glass in the COE range of 90 to 104. Usually, the fluxing agent is Soda and Lime, hence the name, Soda-Lime glass. However, there are other ‘soft’ glasses, such as Leaded glass, which uses Lead Oxide as a fluxing agent. ‘Soft glass’ is suitable for beads, blown work, and sculptural work. And here endeth the science lesson….for the time being!
Here are a couple of sculptures I made recently….
This is my favourite type of glass to touch…….note to self – do not lick the glass.