Borosilicate glass

The addition of just 5-15% of boron – in the form of diboron trioxide (B2O3) or boric acid, (BH3O3) – to a silicate glass improves its mechanical properties, resistance to temperature and thermal shock, electrical resistivity, and resistance to chemicals. Borosilicate glass is not so straightforward to manufacture as soda lime glass, and more expensive, but has become irreplaceable in many applications, such as labware, heat-resistant cookware, solar panels and E-glass fibre for composites. It has superior strength compared to soda lime glass. It doesn’t break so easily when dropped – and when properly made without residual stresses can resist surprisingly high impacts – and can bounce off the floor.

It consumes around half of all boron mined each year. Boron is reasonably expensive – 2-5 usd/g compared to silica sand at around 0.00025 usd/g – which raises the cost of the glass compared to soda lime. While it is consumed in much less significant quantities, partly because it is more expensive, its use in glass fibre for reinforcing composites is unrivalled in terms of volume.