What causes spontaneous glass breakage?

In rare cases, glass can spontaneously break. Join us as we explore why it happens and what you can do to reduce the risk.



Specifying, procuring and installing glass can be complicated. As well as sourcing the right glass for the job, you must specify the correct thickness, provide accurate dimensions and tolerances, navigate compliance, and so on.

All these factors are squarely within your control. Ordering the wrong glass or the wrong size is hardly cause for celebration, but at least you'd know what went wrong and why.

Then there's spontaneous glass breakage. Glass installed weeks, months or even years before can suddenly – and without an obvious explanation – shatter.

This poses an obvious risk to building users, as well as your reputation and the building owner's long-term maintenance budget. And, at least at first glance, it's a problem over which you have no control.

The good news, however, is that the risk of spontaneous glass breakage can almost always be mitigated. All it takes is some careful specification, planning and handling.

In this guide, we look at three of the most common causes of spontaneous glass breakage and explore how you and your glass supplier can help prevent it.

Common causes of spontaneous glass breakage

Nickel sulfide inclusions

Nickel sulfide inclusions are perhaps the most widely recognised cause of spontaneous breakage in toughened glass.

This issue is caused by tiny particles of nickel sulfide that are trapped in the glass during the manufacturing process.

With common-or-garden annealed glass, these inclusions are never an issue. However, the glass toughening process creates internal stress within the glass. If a nickel sulfide particle sits within the centre of the pane, its natural expansion can trigger a catastrophic release of these built-up forces.

The result: the toughened glass pane shatters weeks, months or years after installation – with no obvious trigger.

How to prevent it

Heat soak testing is recognised as the most effective way to reduce the risk associated with nickel sulfide inclusions.

This destructive testing method involves heating toughened glass to around 290°C (554°F) and holding that temperature for around four hours. The glass is then allowed to cool. This effectively provides an accelerated simulation of normal glazing conditions.

Any glass panes affected by nickel sulfide inclusions should break during the test. That means you can be confident that the remaining glass is unaffected.

At ToughGlaze, our heat soak testing procedure results in glass that's 100 times more resistant to spontaneous breakage than untested glass.

Edge damage

Edge damage is a common cause of spontaneous breakage that can affect any type of glass – annealed, toughened or laminated.

It often starts with a tiny chip at the edge of the pane. This damage could be caused by transportation, handling, the installation process or subsequent building work.

The chip is often so small as to be almost invisible. Over time, however, stress can concentrate around the defect until a crack propagates through the pane.

How to prevent it

Shattering caused by edge damage often appears spontaneous because there's typically a delay between the cause of the defect and the ultimate breakage. This often leads to cases being misdiagnosed.

In more positive news, however, it's also one of the most preventable causes of glass failure.

There are several steps you can take before and after the glass comes into your possession.

Before you receive the glass, be sure to specify:

Appropriate edgework: reducing flaws at the edge of the glass reduces potential initiation points for defects.

The right type of glass: laminated glass, for instance, may provide some level of containment after shattering.

Once the glass is in your possession, be sure to exercise good storage, handling, transportation and installation procedures:

• Storage: store panes upright on suitable racks, away from potential sources of damage.

• Handling: avoid dragging glass across hard surfaces, resting it on concrete or allowing glass-to-glass contact.
  
  
• Transportation: use industry-standard protection during transportation, such as edge guards, racking systems and secure restraints.
  
  
• Installation: make sure to inspect edges before installation and ensure proper edge clearance when installed.
  
  
• Thermal stress
  Thermal stress is especially likely to cause glass breakage in large windows and other substantial glazed areas.

This issue occurs when different areas of a glass pane heat up at different rates. Over time, the temperature differences create stresses within the glass.

As a result, the glass may shatter without any obvious impact event – especially on a particularly hot day.

How to prevent it

Mitigating thermal stress can be complicated because it involves close cooperation among procurement, design and installation teams. However, it's far from impossible.

As ever, the first step is choosing the right type of glass. Toughened glass and heat-strengthened glass, for instance, are specially designed to resist thermal stress.

Choosing and installing an appropriate framing system is also important. Make sure to choose one that allows for the glass to expand as it warms. Some framing systems can also contribute to thermal stress by leaving the edge of the glass in shade, so be sure to consider this, too.

And throughout, interior and architectural design considerations should be made. Thermal stress can be increased by all manner of internal and external design elements, including:

• Nearby buildings
• Canopies
• Columns
• Internal blinds
• Dark window films
• Dark fritting or other coloured design elements on the glass
  
  

Thermal stress can't be eliminated entirely – and the larger the glass pane, the more pronounced the problem becomes. However, with careful decision-making that considers design, as well as technical factors, you can effectively manage the risks that come with it.

How we can help

As we've seen, there's much you can do as a glass customer to mitigate against spontaneous glass breakage.

However, you're not alone. One of your biggest allies in the fight against spontaneous breakage is your glass supplier.

At ToughGlaze, we offer:

• Experience: with more than 30 years of industry experience, we can offer expert advice for all manner of glazing applications.

• Trust: we're a trusted supplier to major construction and architecture firms, certified to ISO 9001:2015 for quality assurance.

• Choice: we provide a huge range of glass products and services, including toughened glass, laminated glass and heat soak testing.

• Peace of mind: by cutting, processing and shipping our glass from one state-of-the-art facility, we reduce risk and ensure easy traceability if something does go wrong.

So, if you're looking for high-quality, certified commercial glass solutions, don't hesitate to get in touch with our experts. We'd be delighted to discuss your next project and how we can help.