The heat soak test or heat soak process is used to minimise the risk of spontaneous breakages of heat-treated glass caused by nickel-sulphide inclusions.

In this process, glass panels are placed inside a chamber and subjected to an oven temperature of 290ºC to accelerate nickel sulphide expansion. This causes glasses containing nickel sulphide inclusions to break in the heat soak chamber, thus reducing the risk of potential field breakages. The broken glass can then be recycled and re-manufactured.

During the process 99% of the defective material is destroyed. Using the heat soak test we can filter 99% of the remaining  1%.

Our answer to the problem is the new HST furnace.