Borosilicate glass

Borosilicate glass is a family of glasses in which silicon oxide and boron oxide are important constituents. It is used in laboratory equipment and technical products, among other applications. The term identifies a material, not a particular workshop, pattern or age.

Properties and variations

Low thermal expansion gives many borosilicate glasses good resistance to temperature changes. SCHOTT explains that compositions can be adjusted for different applications. Properties therefore need to be associated with the specific glass type and object. The Corning Museum of Glass also explains that borosilicates are shaped at higher temperatures than ordinary soda-lime glass.

The material name alone does not authorise every kind of heating. On its PYREX laboratory glassware page, Corning distinguishes different products and warns against using damaged glass. A limit or instruction for one laboratory vessel must not be transferred to an older baking dish or an unidentified glass object.

Brand, material and condition

PYREX is a brand name used, among other things, for Corning's borosilicate laboratory equipment. Borosilicate identifies the general material type. A name, logo or letter style should be investigated alongside model, manufacturer and period. Do not use one modern product sheet as evidence for all older glass bearing a related name.

When buying second-hand, record markings, dimensions, chips, scratches and cracks in a condition report. As a practical example, a model number provides a better starting point for finding the correct manufacturer information than a claim that the glass seems heat-resistant. Follow the advice on packing older glass when moving it.

Next step: For glass you are considering selling, see OBA's buying and selling information and provide photographs of the entire object and its markings.

Sources: SCHOTT on borosilicate glass, the Corning Museum of Glass on the material and Corning on PYREX laboratory glassware.