Glass Spontaneous Breakage: Probability and Key Factors

The probability of glass spontaneous breakage and its influencing factors vary depending on the type of glass, manufacturing processes, and usage conditions. Below is a detailed analysis:

1. Probability of Spontaneous Breakage

Standard Float Glass: Low breakage rate, approximately 0.1%–0.3% (1‰–3‰).

Tempered Glass: Slightly higher breakage rate, typically 0.3%–3% (industry-accepted range), mainly due to impurities (e.g., nickel sulfide) or uneven stress distribution.

Laminated/Insulated Glass: If tempered glass is used, the breakage rate is similar to standalone tempered glass, but the interlayer holds fragments together, reducing hazards.

2. Key Influencing Factors
   • (1) Material & Manufacturing Process
     Nickel Sulfide (NiS) Inclusions: A primary cause of tempered glass breakage; expands under temperature changes, creating internal stress.
     Uneven Stress Distribution: Rapid or uneven cooling during tempering can lead to localized stress concentrations.
     Edge Defects: Poor cutting or grinding increases the risk of cracks starting from the edges.
   • (2) Environmental Factors
     Thermal Shock: Sudden temperature changes (e.g., sunlight exposure followed by rain) can induce stress.
     Mechanical Impact: Improper installation, structural deformation, or physical impacts may trigger breakage.
     Installation Stress: Over-tight framing or direct metal contact (especially under thermal expansion).
   • (3) Other Factors
     Glass Thickness: Thicker tempered glass may have slightly higher breakage risk due to greater internal stress.
     Aging: Nickel sulfide inclusions may undergo phase transformation years later, leading to delayed breakage.

3. Mitigation Measures

High-Quality Glass Selection:

Use Heat-Soak Tested (HST) tempered glass, which reduces breakage risk to below 0.1% by eliminating NiS defects.

Opt for laminated glass (even if breakage occurs, fragments remain bonded).

Proper Installation:

Allow expansion gaps; use flexible gaskets to absorb stress.

Avoid Extreme Conditions:

Minimize exposure to rapid temperature changes (e.g., use shading for sun-facing glass).

Conclusion

Spontaneous breakage is rare in standard glass but occurs at a low rate (a few per thousand) in tempered glass. Risks can be significantly reduced through material selection and proper installation. For critical applications (e.g., facades, shower enclosures), heat-soak tested or laminated tempered glass is strongly recommended.