Views: 0 Author: Site Editor Publish Time: 2026-05-18 Origin: Site
Tempered glass spontaneous breakage is a critical concern in modern construction, particularly in curtain walls, facades, and other safety-sensitive applications. If you are unsure whether the glass breakage is spontaneous or caused by external factors, refer to our guide on how to identify spontaneous tempered glass breakage and claim warranty.
Although the risk cannot be completely eliminated, it can be significantly reduced through proper material selection, controlled manufacturing processes, and effective post-treatment methods. This article focuses on Heat Soak Testing (HST) as the most effective solution, and explains how Reach Building minimizes risk through a systematic approach, including raw material control, precision edge processing, optimized tempering, and HST in accordance with EN 14179-1.
By understanding these methods, project developers, contractors, and buyers can make more informed decisions, reduce long-term risks, and ensure higher safety standards in glass applications.
Heat Soak Testing (HST) is an additional process carried out after tempering. It can be understood as a safety check for tempered glass. The purpose is to identify and eliminate panels with potential spontaneous breakage risks before delivery, improving the overall safety of the glass. The process is completed in a dedicated heat soak furnace and typically takes around 8 to 10 hours. It consists of three controlled stages: heating, holding, and cooling. REACH BUILDING is equipped with a dedicated heat soak furnace. All ordered heat soaked (HST) glass is processed in accordance with EN 14179-1 before delivery.
During the heating stage, the furnace air temperature may briefly exceed the target level, while the glass surface temperature is generally kept below 320°C. At the same time, the duration at higher temperature ranges, such as above 300°C, is minimized to avoid affecting the stress profile formed during tempering and to maintain the stability of the glass performance.
Once all glass panels reach the target temperature, the process enters the holding stage. This stage typically lasts at least two hours, with the temperature maintained at 290°C ±10°C. If certain glass panels contain a potential risk of spontaneous breakage, this issue would normally develop gradually over time and may only occur years after installation. Heat soak testing accelerates this process by exposing the glass to a sustained high-temperature environment.
In other words, panels with defects are more likely to break inside the furnace during testing, allowing them to be removed before delivery. Panels that pass this stage have a significantly lower risk of spontaneous breakage in actual use.
After the holding stage, the glass enters the cooling phase and is gradually brought back to room temperature. At REACH BUILDING, the cooling rate is carefully controlled to prevent new thermal stress from forming. When the furnace temperature drops to around 70°C, the furnace is opened and the glass is removed, allowing it to cool naturally to ambient conditions. This controlled cooling process helps maintain the structural stability of the glass.
Heat Soak Testing (HST) process for tempered glass, showing heating, holding, and cooling stages used to reduce spontaneous breakage risk.
In addition to temperature control, several operational details are essential to ensure consistent results. At REACH BUILDING, strict procedures are followed throughout the process:
Glass panels are placed vertically and kept in a free-standing condition to allow natural expansion.
A minimum spacing of 20 mm is maintained between panels to ensure proper air circulation.
Temperature distribution inside the furnace is carefully monitored to ensure uniform heating.
The heat soak process is carried out in accordance with the time–temperature profile shown above.
In practical applications, standard tempered glass typically has a spontaneous breakage rate of around 3‰. After heat soak testing, this risk can be significantly reduced, generally to a range of 0.1‰ to 0.01‰, depending on processing quality and control conditions. This reduction makes heat soak testing one of the most effective methods for minimizing spontaneous breakage in tempered glass.
From a cost perspective, heat soak processing adds an additional 8 to 10 hours to the production cycle, resulting in an increase of approximately 15% to 20% compared to standard tempered glass. However, for projects such as high-rise curtain walls, public buildings with heavy foot traffic, and safety-critical areas, this additional cost is widely considered a necessary investment to improve safety and reduce long-term risks.
In addition to heat soak testing as a post-processing screening method, taking the following measures during production can also significantly reduce the risk of spontaneous glass breakage. Reducing spontaneous breakage is not about one single solution, but a combination of multiple controls throughout the production process. At REACH BUILDING, we approach this as a complete system rather than an isolated step.
We start from the raw material stage by selecting float glass with low impurity levels, which helps reduce the likelihood of internal defects. For projects with higher requirements, ultra-clear glass is also available as an option to further minimize risk. To ensure quality consistency, material sources can be verified, and key parameters such as impurity levels are controlled and traceable throughout production.
Before tempering, all panels undergo precision edge processing. This step removes micro-cracks created during cutting and ensures a smooth and uniform edge. Since edges are the most vulnerable part of glass, proper finishing plays an important role in preventing future breakage.
During tempering, we closely monitor furnace conditions, including temperature uniformity and cooling balance. This ensures that stress is distributed evenly across the glass, resulting in stable and consistent performance across all panels.
At REACH BUILDING, we combine material selection, precision processing, controlled tempering, and standardized heat soak testing to significantly minimize potential risks before delivery. This integrated approach ensures that the glass used in your project meets both safety and performance expectations. For high-rise buildings, curtain walls, and other safety-critical applications, choosing the right glass solution is not just a technical decision, but a long-term investment in safety and reliability.
If you are working on a project that requires tempered or heat soaked glass, feel free to contact our team. We are ready to provide tailored solutions based on your specific requirements.
For readers who want to better understand how to identify spontaneous tempered glass breakage in real projects, we also provide a detailed guide on warranty claims, breakage patterns, and common causes of glass failure.
Read more: How To Identify Spontaneous Tempered Glass Breakage And Claim Warranty
Q: Can heat soak testing completely eliminate spontaneous breakage?
A: No, heat soak testing cannot completely eliminate the risk, but it can significantly reduce it by removing most high-risk panels before delivery.
Q: What is the spontaneous breakage rate of tempered glass?
A: Standard tempered glass typically has a spontaneous breakage rate of around 1‰ to 3‰. After heat soak testing, this can be reduced to approximately 0.1‰ to 0.01%, depending on processing quality.
Q: Is heat soaked glass necessary for all projects?
A: Not necessarily. For high-rise buildings, curtain walls, and public spaces, heat soaked glass is strongly recommended. For standard residential use, tempered glass may be sufficient.
Q: What is the difference between tempered glass and laminated glass in terms of safety?
A: Tempered glass is stronger and breaks into small fragments, while laminated glass holds together after breakage due to its interlayer. Laminated glass provides better protection against falling glass hazards.
