Characteristics of oxide glasses

fused silica soda-lime-silica borosilicate aluminosilicate lead

Approximate composition¹

● silica 99.9%

● water 0.1%

● silica 73%

● alumina 1%

● sodium oxide 17%

● magnesia 4%

● lime 5%

● silica 81%

● alumina 2%

● boric oxide 13%

● sodium

oxide 4%

● silica 62%

● alumina 17%

● boric oxide 5%

● sodium oxide 1%

● magnesia 7%

● lime 8%

● silica 56%

● alumina 2%

● sodium oxide 4%

● potash 9%

● lead oxide 29%

coefficient of thermal expansion (linear expansion per degree Celsius 【10⁷】) 5.5 93 33 42 89

strain point² (degrees Celsius; viscosity about 10^14.5 poise) 990 470 515 670 395

annealing point³ (degrees Celsius; viscosity about 10¹³ poise) 1,050 510 565 715 435

softening point^{4, 5} (degrees Celsius; viscosity about 10^7.65 poise) 1,580 695 820 915 630

Young's modulus (pounds per square inch 【10⁶】) 10.5 10 9.1 12.7 8.6

refractive index (for sodium D line) 1.459 1.512 1.474 1.530 1.560

dielectric constant (at 10⁶ cycles per second and 20 degrees Celsius) 3.8 7.2 4.6 7.2 6.7

density (grams per cubic centimetre) 2.20 2.47 2.23 2.52 3.05

¹These compositions are typical of the various glass types.

²Temperature at which internal stresses are reduced significantly over a few hours.

³Temperature at which internal stresses are reduced significantly over a few minutes.

⁴Temperature at which glass will rapidly deform under its own weight.

⁵The strain point and annealing point roughly define the annealing range.