Borosilicate Glass (Pyrex)

Low thermal expansion glass containing boron trioxide.

Core Principles & Analysis

• Otto Schott developed the first borosilicate glass in Jena in 1893, and Corning introduced the Pyrex brand in 1915.
• Its thermal expansion of about 3.3 ppm/°C is one-third that of soda-lime glass, giving it strong resistance to thermal shock.
• The 200-inch mirror blank of the Hale Telescope on Palomar Mountain was cast from Pyrex by Corning in 1934.

Specifications & Metrics

• DENSITY: 2.23 g/cm³
• YIELD STRENGTH: N/A (brittle)
• HARDNESS: 480 HK