Heat-soaked test

Nickel sulfite inclusions may be present in float glass. This contaminant is known to cause spontaneous breakage. The Heat Soak process consists of reheating tempered glass in a different oven, to cause the glass to break in the presence of nickel sulfite.

What is Heat-soaked Test

reduce the risk of spontaneous breakage in tempered glass

Heat-soaked glass, HST, is tempered glass that is heated to eliminate any glass that is subject to spontaneous breakage, before installation.  The HST test identifies glass batches with a high incidence of nickel sulfide inclusions, a contaminant responsible for spontaneous breakage. This type of glass is suitable for difficult-to-access locations, high elevations, or spaces that require extra protection, such as structural glass building facades.



Why Choose AJJ

The Power of Quality

Highest Quality Tempering Furnaces

AJJ employs a fleet of world-class tempering furnaces across the enterprise. Our tempering furnaces give us the ability to produce high-quality heat-treated glass products consistently.

Oversize Capabilities

Our facilities and processes are carefully designed to handle the production of oversized heat-treated glass without compromising quality or durability.

Flatter Glass

Optical distortion is an inherent feature associated with heat-treated glass. Through AJJ’s commercial glass facilities, optical distortion is more effectively monitored and controlled. With cutting-edge optical distortion measurement equipment being used as a critical part of our quality control inspection process, AJJ can consistently put out optically flatter glass.

Fast Glass

We have multiple shifts working around the clock to meet your schedule and your project needs. Ask your sales representative about our expedited lead times for monolithic heat-treated glass products.

Key Features of Heat-treated Glass

Key Product Features

Meets Building Code Requirements

Using tempered glass can reduce the probability of serious injury in areas where human impact is probable. It can be used in applications where safety glazing is required by code, and it is widely used in shower doors, building entrances, glass railings and balustrades, vision and spandrel areas, and skylights.

Improved Resistance Against Thermal Stress

Using heat-strengthened and tempered glass on your project gives you a building product that is more resilient against exposure to temperature extremes and differential shading conditions.

Improved Resistance Against Shock

Where greater impact resistance is necessary, consider using heat-strengthened glass products. For any commercial glazing application, AJJ recommends the use of heat-treated glass.

Improved Resistance to Loads

The heat-treating glass increases its resistance to wind and snow loads. This improved performance can be critical when glass is used in structurally-glazed applications.

HST Technical Specifications

Applications, Production Capacity & Considerations

  • Structural glass, skylights, atriums
  • High-value-added sealed units
  • Glass located in hard-to-reach locations


  • 4mm to 19mm  - Toughened 

  • Minimum Size: 300 x 300mm
  • Maximum Size: 3660 x 18000mm

  • BS EN 14179-1:2016 - This European Standard specifies the heat soak process system together with tolerances flatness, edgework, fragmentation and physical and mechanical characteristics of monolithic flat heat soaked thermally toughened soda lime silicate safety glass for use in buildings.

Get in touch with our team to get a quote or free sample now