Spontaneous Toughened Glass Breakage

Broken Toughened Glass

Spontaneous Toughened Glass Breakage refers to the unexpected and sudden shattering of tempered (toughened) glass without any apparent cause such as impact or stress. This phenomenon, though relatively rare, can be alarming and perplexing for observers. Below is an overview of the causes and preventive measures related to spontaneous glass breakage.


  1. Nickel Sulfide (NiS) Inclusions:
    • During the manufacturing of glass, tiny impurities, such as nickel sulfide crystals, can be trapped within the glass.
    • These inclusions can expand at different rates than the surrounding glass when subjected to temperature changes, leading to internal stress.
    • Over time, this stress can cause the glass to shatter spontaneously.
  2. Edge Damage:
    • If the edges of tempered glass are damaged during installation or through contact with hard surfaces, micro-cracks may form.
    • These cracks can slowly propagate through the glass, eventually leading to breakage.
  3. Thermal Stress:
    • Uneven heating of the glass surface, such as when one part is in direct sunlight while another part is in shade, can cause thermal stress.
    • The stress created by the temperature differential may lead to spontaneous breakage.
  4. Manufacturing Defects:
    • Imperfections or defects during the manufacturing process, such as inadequate annealing or cooling, can leave residual stresses in the glass.
    • These stresses can lead to spontaneous breakage.

Preventive Measures and Solutions:

  1. Heat Soak Testing:
    • Heat soaking is a process where tempered glass is subjected to elevated temperatures to induce breakage of any pieces that might have nickel sulfide inclusions.
    • This can significantly reduce the risk of spontaneous breakage after installation.
  2. Proper Installation:
    • Ensuring that the glass is installed without causing edge damage and using compatible and non-abrasive materials can minimize the risk of breakage.
  3. Safety Films:
    • Applying safety films on tempered glass can help hold the shattered pieces together if breakage occurs, reducing the risk of injury.
  4. Quality Control:
    • Rigorous quality checks during manufacturing can help identify and rectify defects that might lead to spontaneous breakage.


While spontaneous toughened glass breakage is uncommon, understanding its causes and taking preventive measures can help mitigate risks and ensure the safety and longevity of glass installations.


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