Useful Information about Architectural Glazing

Nickel Sulphide Inclusion

What is Nickel Sulphide Inclusion?

Nickel Sulphide Inclusion (NSI) is a rare impurity that can occur in toughened glass, potentially leading to spontaneous breakage. These tiny metallic particles are invisible to the naked eye but can pose a significant risk in certain conditions.

How Does Nickel Sulphide Inclusion Occur?

  1. High-temperature stable state – Formed during the glass manufacturing process.

  2. Low-temperature stable state – The final, natural state of the inclusion at ambient temperatures.

During the glass toughening process, NSI is trapped in the high-temperature state. As the glass cools rapidly, the inclusion does not have time to revert to its low-temperature state. Over time, however, it gradually transforms, causing an expansion that can result in spontaneous glass breakage if the inclusion is located within the tensile (central) zone of the glass panel.

How to Identify Nickel Sulphide Inclusion Breakage

One of the most common indicators of NSI-induced glass breakage is the Butterfly Effect pattern. This distinctive breakage pattern features a singular fracture point with cracks fanning out symmetrically, resembling butterfly wings. However, confirming an NSI-related failure requires professional glass analysis.

How to Reduce the Risk of Nickel Sulphide Inclusion Breakages

Heat Soaking Process 

Since NSI cannot be entirely eliminated, a secondary process known as Heat Soaking significantly reduces the risk of breakage.

What is Heat Soaking?

Heat Soaking (EN 14179) is a controlled thermal treatment process that exposes toughened glass to temperatures of 290°C (+/- 10°C) inside a heat soaking oven. This accelerates the transformation of Nickel Sulphide Inclusions, causing panels with impurities to shatter in a controlled environment rather than after installation.

Effectiveness of Heat Soaking

While no process can completely eliminate the risk, Heat Soaking reduces the likelihood of NSI breakages to 1m² in every 1 million m² of glass, compared to the standard risk of 1m² in every 10,000m² of glass (as estimated by the Glass and Glazing Federation, GGF).

Considerations for Heat Soaking

  • Heat soaking increases costs and extends lead times.

  • It is recommended for critical glass installations, such as inaccessible panels or glazing elements that would be costly or difficult to replace.

  • Architects can specify heat-soaked glass for construction projects where spontaneous breakage poses a concern.

 

large structural glass window

Warranties & Insurance Coverage for Nickel Sulphide Breakages

Despite the advancements in glass manufacturing, Nickel Sulphide Inclusion remains an unpredictable phenomenon. Glass manufacturers and suppliers do not offer warranties against NSI-related breakages.

What Can You Do?

  • Check your insurance policy: Many home insurance policies cover spontaneous glass breakage. Confirm with your provider to ensure coverage.

  • Specify heat-soaked glass: This minimises risk, particularly for projects where glass replacement would be challenging.

Guardian Glass UK Statement on Nickel Sulphide Inclusion

Guardian Industries UK Ltd acknowledges the difficulty of completely eliminating nickel contamination, which can sometimes lead to localized NSI outbreaks. Due to the nature of the phenomenon and the absence of reliable detection methods, Guardian does not provide a warranty against NSI-related breakage.

crane lift for curved glass

Final Recommendations

To minimise the risk of Nickel Sulphide Inclusion breakages:

  • Always consider Heat Soaking, especially for high-risk applications.

  • Consult with IQ Glass before specifying materials for your project.

  • Ensure insurance coverage includes protection against spontaneous breakage.

For further research, you can explore more about the scientific studies on Nickel Sulphide Inclusion and its impact on glass performance.

Need More Information?

If you're working on a project and need expert advice on specifying heat-soaked glass, feel free to reach out to a member of our team. Ensuring your glass is as safe and reliable as possible is essential for both aesthetics and structural integrity.

You can read more about the scientific study and investigation into the Nickel Sulphide phenomenon here.

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