Borosilicate Glass 3.3
A chemically and thermally shock-resistant glass
Typical values for the temper in the title
Borosilicate 3.3 is the common technical glass: about 80% silica and about 13% boron oxide. Its expansion (3.3×10⁻⁶/K) is 3 times lower than ordinary glass, so it resists moderate thermal shock. It is highly resistant to water, acids and organic substances.
It is used for labware, piping and equipment in the chemical industry, hot sight windows and covers, and lighting. Continuous service (non-tempered) is up to about 450 °C, and the softening point about 820 °C.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Modulus of elasticity E | 63 GPa | |
| Density ρ | 2.23 g/cm³ | |
| Vickers hardness HV | 580 | |
| Thermal expansion | 3.3×10⁻⁶/K | |
| Continuous service | up to about 450 °C (non-tempered) | |
| Machinability | Grinding and diamond only | relative rating in the site database |
Structure and production
| Feature | Value | Meaning |
|---|---|---|
| SiO₂ | about 80% | |
| B₂O₃ | about 13% | low expansion |
| Na₂O / Al₂O₃ | about 4% / about 2% | |
| Expansion | 3.3×10⁻⁶/K |
Typical values per producer data.
Grades and production routes
In technical glasses, the choice is by thermal expansion, service temperature and required transparency.
| Version | Properties | When to choose it |
|---|---|---|
| Non-tempered | up to about 450 °C long term | labware and piping |
| Tempered | stronger, for lower heat | windows and covers |
Applications
- Laboratory glassware
- Chemical piping and equipment
- Hot sight windows
- Lighting
- Covers and guards
Fabrication
Brittleness
Ceramics do not deform before fracture: they break suddenly from a small flaw, so strength scatters widely. Avoid sharp corners, tensile stresses and shock, and prefer compressive loading.
Thermal shock
Resists moderate shock (about 180 K per Continental), less than fused silica.
Machining
By grinding and diamond tools.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| Fused Silica | — | Flame working (glass) | fused silica: for much higher heat and shock · material page |
| PMMA (Acrylic) | 72 MPa | Solvent / Ultrasonic | PMMA: transparent, light, not heat resistant · material page |
| PC (Polycarbonate) | 65 MPa | Ultrasonic | polycarbonate: transparent and impact resistant · material page |
Common mistakes
Heating above about 450 °C long term
For higher heat, fused silica.
Exposing it to large thermal shock
It may crack.
Using it in hydrofluoric acid or hot concentrated alkali
They attack glass.
Equivalents, standards and supply
| ISO | 3585 (Borosilicate 3.3) |
|---|---|
| Standards | ISO 3585 |
| Forms | tube · sheet · labware |
| Producers | Schott (Duran, Borofloat) · Corning (Pyrex) |
Learn more
Values are typical and for comparison only. In ceramics, strength is measured in bending and scatters widely (depending on flaws and finish), so design to producer data with suitable safety factors. Sources: ISO 513, ISO 13356, ASTM F603, producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026