Nickel sulphide inclusion

A few years ago, it was scientifically proven that glass could break spontaneously as a result of nickel sulphide inclusion. Nickel sulphide (NiS) is present in raw materials used in the production of glass. NiS has the tendency to crystallize during the heat treatment process. The toughening of glass is a process whereby the glass is heated at a considerable temperature (± 700° C). The cooling phase causes stress in the glass and the existing NiS molecules crystallize. The pressure exerted by these crystals can cause the glass to break. This phenomenon can occur even after a number of weeks.

During the production of Safety Glass, faults in products do, of course, occur. The production process always ends with the cooling of the glass. During this cooling process, faulty products break almost immediately. Production loss is a normal occurrence. The few faulty products that do not break usually break hours after production during handling.   We cannot determine that nickel sulphide is a possible cause of some production loss, since other obvious causes occur more frequently.

The entire project logistics, from production up to and including delivery by Zijlstra, takes a minimum of 6 weeks. It is unfortunate that some products break during this process. We cannot rule out the fact that breakages could be as a result of nickel sulphide inclusion, however, we cannot determine this. The cause of breakage, also at Zijlstra, is practically always due to a fall or accidental knock.

Because other causes of breakage during production and logistics are also familiar to us, we can conclude that breakage due to the nickel sulphide phenomenon seldom occurs at Zijlstra. The possibility that you will be confronted with this phenomenon is, therefore, minimal.  Breakages as a result of nickel sulphide inclusion will, in principle, occur during the time that the product is still in our possession.

Despite the existence of NiS inclusion, we continue to fully support our product. The alternative – untoughened glass – is arguably much more dangerous than a product that, in exceptional cases, “spontaneously” shatters.