Glass

Glass strength, stiffness, density and thermal properties, with their source.

A panel in Glass, smooth finish.

Mechanical
Yield strength	none (brittle)
Ultimate tensile strength	41MPa1
Flexural strength	mean MOR41MPa1
Elongation at break	none (brittle)
Young's modulus (stiffness)	72GPa1
Density	2,500kg/m³1
Strength to weight	16.4kN·m/kg
Stiffness to weight	28.8MN·m/kg
Poisson's ratio	0.221
Shear modulus	29.5GPa
Bulk modulus	42.9GPa
Speed of sound	5,367m/s

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal
Thermal conductivity	0.937W/m·K1
Thermal expansion	8.3µm/m·K1
100 mm part over a 50 °C swing	41.5µm growth
Specific heat	880J/kg·K1
Heats up and cools (diffusivity)	0.426mm²/s
Thermal shock resistance	50.1W/m
Max service temperature	strain point511°C1

Thermal conductivity against densityHigher and further left: spreads more heat for its weight

Thermal expansion against thermal conductivityLower and further right: warps less when heated

Sources1 document: Pilkington North America

Values for: Natural. Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025)

1
Technical Bulletin ATS-129: Properties of Soda-Lime Silica Float Glass (2025)Pilkington North Americaarchived copyUltimate tensile strength: typical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probabilityFlexural strength: mean MOR (same value as tensile)Young's modulus (stiffness): typicalDensity: typicalPoisson's ratio: typicalThermal conductivity: typical at 75 FThermal expansion: typical, 75-575 FSpecific heat: typical at 75 FMax service temperature: strain point (ASTM C336) - stress-relaxation onset, not a rated service limit

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Thermal properties of Glass

Thermal conductivity of Glass

Glass has a thermal conductivity of 0.937 W/m·K (0.541 BTU/hr·ft·°F). Basis: typical at 75 F. Source: Pilkington North America, Technical Bulletin ATS-129: Properties of Soda-Lime Silica Float Glass (2025)archived copy.

Specific heat of Glass

The specific heat capacity of Glass is 880 J/kg·K (0.21 BTU/lb·°F). Basis: typical at 75 F. Source: Pilkington North America, Technical Bulletin ATS-129: Properties of Soda-Lime Silica Float Glass (2025)archived copy.

Coefficient of thermal expansion of Glass

Glass expands 8.3 µm/m·K (4.61 µin/in·°F): a 100 mm part grows 41.5 µm over a 50 °C rise. Basis: typical, 75-575 F. Source: Pilkington North America, Technical Bulletin ATS-129: Properties of Soda-Lime Silica Float Glass (2025)archived copy.

Thermal diffusivity of Glass

Computed from the conductivity, density and specific heat (k / ρc): 0.426 mm²/s, how fast a temperature change spreads through it.

Maximum service temperature of Glass

The maximum service temperature of Glass is 511 °C (952 °F). Basis: strain point (ASTM C336) - stress-relaxation onset, not a rated service limit. Source: Pilkington North America, Technical Bulletin ATS-129: Properties of Soda-Lime Silica Float Glass (2025)archived copy.