Nickel Sulphide Inclusions: Why Toughened Glass Can Shatter Spontaneously

While rare, nickel sulphide inclusions are a recognised characteristic of toughened glass and are one of the leading causes of spontaneous glass breakage worldwide.

What Are Nickel Sulphide Inclusions?

Nickel sulphide inclusions are microscopic particles that can form during the glass manufacturing process when trace amounts of nickel and sulphur combine within the molten glass.

These particles are incredibly small and cannot be seen during normal inspection. Once the glass is toughened, the inclusion becomes trapped within the glass structure.

Over time, changes within the particle can cause it to expand, generating stress inside the glass panel. If the stress exceeds the strength of the toughened glass, the panel may shatter suddenly and without any external impact.

Why Does This Only Affect Toughened Glass?

The toughening process involves heating glass to extremely high temperatures before rapidly cooling the surfaces. This creates the compressive stresses that give toughened glass its strength and safety characteristics.

However, these same internal stresses can make the glass susceptible to expansion caused by a nickel sulphide inclusion. As the inclusion grows, the stored energy within the glass is released, causing the panel to break into the small, relatively harmless fragments expected of safety glass.

Not Every Breakage Is Caused by Nickel Sulphide

While nickel sulphide inclusions are a recognised cause of spontaneous breakage, they are not the only reason a toughened glass panel may fail.

Other factors that can contribute to glass breakage include:

• Edge damage sustained during handling, transport, or installation
• Surface damage that weakens the glass over time
• Excessive pressure from glazing systems, fittings, or hardware
• Building movement or frame deflection
• Thermal stress caused by uneven heating
• Accidental impact or vandalism

In some cases, damage may occur long before the glass eventually breaks, making the original cause difficult to identify.

Identifying Nickel Sulphide Breakage

When spontaneous breakage occurs, a trained glazing professional can often identify whether a nickel sulphide inclusion was the likely cause by examining the fracture pattern and origin of the break.

One of the most recognised indicators is a distinctive "butterfly" pattern found at the point where the break originated. Detailed inspection may be required to confirm the presence of an inclusion.

Expert Advice and Replacement Solutions

If a toughened glass panel has shattered without an obvious cause, professional assessment is recommended. Determining the source of the breakage is important when selecting an appropriate replacement solution.

If a toughened glass panel has shattered unexpectedly, the team at Tough Glass can provide replacement glass solutions and expert guidance to ensure the right product is selected for your application.

Understanding nickel sulphide inclusions helps explain why spontaneous glass breakage can occur and highlights the importance of working with experienced glazing professionals when specifying and replacing toughened glass.