Published: 23rd November 2023

Glass isn’t a perfect product. There are minuscule imperfections in all glass panes. It is impossible to remove all these imperfections.

One of these imperfections can be nickel sulphide. When glass is ‘toughened’ it is heated to an incredibly high temperature followed by a rapid cooling process. During this cooling process the nickel sulphide within the glass shrinks. Sometimes over the course of the glass’s lifetime, the nickel sulphide can expand back to its normal state creating huge stress on the glass panel and this is when an effect called ‘spontaneous breakage’ can occasionally occur. The glass will literally break out of nowhere and apparently for no reason. very expensive bespoke glass panel. If this glass is in an overhead rooflight, this can obviously be very dangerous causing severe injury to people below or damage to furniture and fittings, not to mention destroying the very expensive glass panelled rooflight itself.

Luckily there is a way to avoid this. Your rooflight supplier can do what is called a ‘destructive heat soak test’ on individual glass panes. Heat soaking is a ‘destructive process’ where the glass panel is put into a heat soak testing oven. It is then heated to a temperature of approximately 290 degrees Celsius for between 2-4 hours. With glass panes which include nickel sulphide ‘stones’, the heating process will cause the nickel sulphide to expand to its normal state and thus these imperfect glass panels will break in a controlled factory environment rather than when the rooflight is installed in the field.

Unfortunately the heat soak testing process takes time and money adding cost to the final skylight product, so many rooflight suppliers will not carry out this procedure.

At Ofset, we do not believe in cutting corners and therefore all our glazing products are heat soak tested to standard BSEN 14179.

If you invest in an Osfet product, you can be reassured we pay attention to every detail to supply the best, safest, strongest frameless flat rooflights on the market.

The Devil is truly in the detail.