1. What Is Borosilicate Glass?
Borosilicate glass is a technical glass with high silica content and added boron oxide. Its intrinsic structure provides chemical durability and excellent thermal resistance.
Typical Composition
- Silica (SiO₂): 70 - 80%
- Boron oxide (B₂O₃): 7 - 13%
- Alkali oxides: 4 - 8%
- Alumina (Al₂O₃): 2 - 3%
Key Properties
- Exceptional thermal shock resistance
- High chemical inertness
- Optical clarity
- Very low thermal expansion
2. Why Borosilicate Is the Standard for Laboratories?
Borosilicate glass supports demanding environments such as:
- analytical chemistry
- pharmaceutical QC
- food & cosmetics industry
- pilot installations
ISO 3585 defines the requirements for 3.3 borosilicate, considered the global standard for scientific volumetric and thermal-resistant glassware.
3. How Borosilicate Glass Is Manufactured
Production Steps
- Mixing raw materials
- Melting at 1,600 - 1,650 °C
- Refining and homogenisation
- Controlled annealing
- Forming (moulding, blowing, tubbing)
- Quality controls: internal stress, optical purity, dimensional accuracy
Importance of Annealing
Correct annealing ensures
- Mechanical strength
- Volumetric accuracy
- Thermal stability
4. Technical Differences Between 3.3, 5.1 and 7.1
Borosilicate 3.3
ISO 3585 standard- Expansion: 3.3 × 10⁻⁶/K
- Highest thermal resistance
- Excellent chemical durability
- Volumetric glassware
- Heated items, autoclaving
- Precision work
Borosilicate 5.1
- Expansion: 5.1 × 10⁻⁶ /K
- Improved mechanical shock resistance
- High durability
- Glassware handled very frequently
- Tubes, columns, chemistry setups
- Long pieces or pieces exposed to impacts
Borosilicate 7.1
- Expansion: 7.1 × 10⁻⁶/K
- Very good general durability
- Cost-effective option
- Routine glassware
- Applications without moderate thermal cycles
- High-volume Glassware
5. Comparison Table
| Property | BORO 3.3 | BORO 5.1 | BORO 7.1 |
|---|---|---|---|
| Expansion (10⁻⁶/K) | 3.3 | 5.1 | 7.1 |
| Thermal resistance | ★★★★★ | ★★★★☆ | ★★★☆☆ |
| Mechanical strength | ★★★★☆ | ★★★★★ | ★★★★☆ |
| Volumetric precision | ★★★★★ | ★★★☆☆ | ★★☆☆☆ |
6. Selecting the Right Grade
For heating/autoclaving choose BORO 3.3
For frequent handling choose BORO 5.1
For standard use choose BORO 7.1
7. Conclusion
Borosilicate glass remains essential for reliable, reproducible and safe laboratory work. Grades 3.3, 5.1 and 7.1 provide different balances of precision, robustness and thermal tolerance. AllChimie's CrystAll line offers glassware manufactured from high-quality borosilicate and compliant with strict international standards.