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What is Heat Soaked Glass?

Posted on 3rd August 2023

There are many distinct glass types, which are primarily the result of the various processes and tests that the glass goes through to attain its final specification.

An increasingly common glass variant is ‘Heat Soaked Glass’.

So, what exactly is Heat Soaked Glass and why is it relevant to Balustrades?

Heat soaking refers to a thorough test that the glass is put through. It has no effect on the strength of the glass; rather, it minimises the chance of spontaneous glass breakage in service.

What does the test do?

It is a destructive test used to detect the presence of nickel sulphide (NiS) inclusions. It entails placing the toughened glass into an oven and heating it to around 290oC. The glass is kept at this temperature for a long enough amount of time to fracture a large proportion of any panes that might otherwise have failed in service.

Shattered Glass Panel

It’s worth noting that this test only identifies NiS inclusions. Other inclusions, such as silica, which can potentially cause breaking, will not be detected.

Is Heat Soaked Glass a requirement for Glass Balustrade Systems?

Heat-soak testing is not singularly required by any British Standard, but it is recommended for safety-critical balustrade installations such as:

  • Atrium glazing and balustrades that prevent people from falling,
  • Overhead glazing,
  • Highly trafficked areas such as airports and other high-profile areas where breakage would be highly emotive.

Concluding Remarks

In conclusion heat soaked glass refers to glass that has been through destructive testing to pre-emptively break panels that could have otherwise broken in service due to nickel sulphide inclusion. It reduces the chance of a failure by around 100x – but doesn’t make the glass any stronger.

For more information on Nickel Sulphide inclusions and what these are, please see our article: ‘What are Nickel Sulphide Inclusions in Glass?‘.

Additionally, if you’d like to stay up to date with the newest industry knowledge, keep an eye on our learning centre here.