Borosilicate glass was first developed by German glassmaker Otto Schott in the late 19th century and sold under the brand name “Duran” in 1893. After Corning Glass Works introduced Pyrex in 1915, the name became a synonym for borosilicate glass in the English-speaking world. The European manufacturer of Pyrex, Arc International, uses borosilicate glass in its Pyrex glass kitchen products.

Borosilicate glass is widely used for laboratory glassware, either mass produced or as custom made.

Borosilicate glass has excellent thermal properties with its low coefficient of expansion and high softening point, it also offers a high level of resistance to attack from water, acids, salt solutions, organic solvents and halogens. Resistance to alkaline solutions is moderate and strong alkaline solutions cause rapid corrosion of the glass, as does Hydrofluoric acid and hot concentrated Phosphoric acid.

Chemical Composition

SiO2 = 80.6%
B2O3 = 13.0%
Na2O = 4.0%
Al2O3 = 2.3%

Optical Information

Refractive index (Sodium D line) = 1.474
Visible light transmission, 5mm thick glass = 91%
Visible light transmission, 2mm thick glass = 92%

Physical Properties

Coefficient of expansion (20°C–300°C) 3.3 x 10-6 K-1
Density 2.23g/cm3
Refractive index (Sodium D line) 1.474
Dielectric constant (1MHz, 20°C) 4.6
Specific heat (20°C) 750J/kg°C
Thermal conductivity (20°C) 1.14W/m°C
Poisson’s Ratio (25°C – 400°C) 0.2
Young’s Modulus (25°C) 6400 kg/mm2