Ridhi Sidhi Heat Soaked Glass can be used in critical application areas to eliminate the risk of spontaneous breakage. Nickel Sulphate (NIS) has been known to be the cause of spontaneous burst in Tempered Glass / Toughened Glass. During tempering the invisible nickel sulphide present in the glass is transformed to the high tempered a- phase (t>380C) and has no time to return to the ß- phase on quenching. With the passage of time, it slowly inverts to the low-temperature ß- phase with the increase in the volume of about 4%. This volume expansion may cause glass breakage. The heat soak is a destructive treatment which heats the glass for several hours at about 290 degrees C to speed up the -NAS to ß – NiS transformation and consequently forces the contaminated glasses to break within the oven.