When ordering toughened glass you’ll often see “heatsoaking” as an option. Here’s exactly what it is and whether it’s worth it for your project.
Heatsoaking is an additional factory test that dramatically reduces the already small risk of spontaneous breakage in toughened glass. It is highly recommended for glass in difficult-to-replace locations.
What causes spontaneous breakage?
During glass production, microscopic nickel sulphide (NiS) inclusions can become trapped inside. Toughening freezes these inclusions under stress. Over months or years, temperature fluctuations can cause them to expand and trigger sudden, unexplained shattering.
What does heatsoaking actually do?
After toughening, the glass is placed in a special oven and held at approximately 290°C for several hours. Any panels containing dangerous NiS inclusions will shatter in the factory — not on your site. Panels that survive the process have an extremely low risk of spontaneous breakage later.
When is heatsoaking recommended?
Heatsoaking is optional but strongly advised for:
- High-level glazing (roof lights, high windows, atriums)
- Structural glass (floors, stair treads, balustrades)
- Large commercial or hard-to-access installations
- Any situation where replacing a broken pane would be expensive or disruptive
For easily accessible glass like standard shower screens or ground-floor windows, it is usually not necessary.
Does heatsoaking affect the glass?
No. It does not change the appearance, strength, or performance of the glass in any way. It is purely a quality assurance process. It adds a small cost and a few days to lead time, but delivers significant peace of mind.
Browse Toughened Glass with Heatsoaking
Configure and order heat-soaked toughened glass here: Toughened Glass Collection
Questions you might still have
Q: Does heatsoaking guarantee the glass will never break?
A: No. It almost eliminates the risk of spontaneous breakage from nickel sulphide inclusions, but the glass can still break from impact or edge damage.
Q: Can laminated glass be heatsoaked?
A: Yes. The individual toughened panes can be heat-soaked before lamination — highly recommended for structural laminated glass.
Q: How common is spontaneous breakage?
A: Relatively rare, but when it happens it is sudden and without warning. Heatsoaking acts as very effective insurance for high-value or difficult installations.
Unsure if your project needs heatsoaking?
Use our instant calculator to price toughened glass with or without heatsoaking.
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