Most of us are more familiar with this type of glass in the form of ovenware and other heat-resisting ware, better known under the trade name Pyrex.
Borosilicate glass (or sodium-borosilicate glass) is made mainly of silica (70-80%) and boric oxide (7-13%) with smaller amounts of the alkalis (sodium and potassium oxides) and aluminium oxide.
This type of glass has a relatively low alkali content and consequently has both excellent chemical durability and thermal shock resistance - meaning it doesn't break when changing temperature quickly.
As a result of these properties, sodium borosilicate glass is widely used across the chemical industry, pharmaceutical sector for laboratory apparatus, for ampoules and other pharmaceutical containers, various high intensity lighting applications and as glass fibres for textile and plastic reinforcement - as well, of course, for common household oven and cookwares.
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Many glass making terms have entered the language: 'Shut yer gob': a molten lump of glass is called a 'gob' to which the glass blower attached a tube to blow the glass into shape. The blower had to blow hard which made his cheeks very large. Today someone with a big mouth is told they have a big gob.