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What is a spontaneous glass breakage

Occasionally we hear stories, seams as urban myths, of mysteriously shattered glass touched by no one and without any apparent reason. Some relate this to all kinds of supernatural occurrence and even to ghosts' presence.

 It's important to clarify from the beginning, this phenomenon does happen, but has nothing to do with spiritual beings or any other supernatural event!

 This phenomenon is named a spontaneous glass breakage, and it occurs only in Tempered glass, that is suddenly shattered, during it's life span and even years after the glass is already installed in the frame, and seemingly without reason.

 There are many reasons for this occurrence that can be related to:

  • A minor damage in the edge of the tempered glass
  • A small nick or chip of the glass surface, caused during the glass transport or its installation.

A combination of these minor and often unseen damages could deteriorate the glass, along with the glass units' movements (caused by winds and temperature changes, because of wrong frame planning), could lead to a spontaneous shatter.


Another, but very rare option, is the presence of a Nickel Sulfide molecule NiS in the raw material of the glass.

During the tempering process of the glass that is manufactured in a float line, the glass is heated to a high temperature and then quickly cooled.

The result is tempered glass, that is 4 times stronger than was originally.

The tempering process causes the external layers of the glass to shrink on top of its internal layers, this pressure makes the glass stronger.


When tempering a glass containing Nickel Sulfide, this will cause the molecule to contract, and during the cooling process it will be "embedded" that way, so it could not return to its natural size. But it will always strive to return to its natural size.

In extreme conditions of major differences between indoor and outdoor temperature (such as a very hot day outside and a very conditioned room inside, or vice versa), it could happen that the molecule will succeed to expand back, and the result will be a glass breakage.

 Although these are very rare occurrences, Phoenicia recommends these preventive actions:

  • Transfer the glass through a "Heat Soak" process. which by means of controlled heating in a special furnace, simulating extreme conditions, that allow the molecule to expand back. This is a process of destruction, if the glass contains the molecule it will explode in the furnace. It is important to remember that this process greatly reduces the feasibility of this phenomenon but does not eliminate it.
  • Because this phenomenon occurs only in tempered glass, it is recommended to use laminated safety glass (Triplex) except for places where the standard requirements are tempered glass only.
  • Purchase glass only from a certified manufacturer who meets the standards and monitors the production process regularly, to reduce the possibility of Nickel Sulfide in the glass mixture.

 The glass Phoenicia manufactures is sold in Israel and around the world, so Phoenicia is certified to manufacture glass according to Israeli and international standards that define the method and process of production, to minimize the possibility that this molecule will find its way into the glass. In addition, the production line is regularly monitored using sophisticated means, such as magnets and metal detectors, also even the facilities used in the production process do not contain the Nickel Sulfide molecule.

We in Phoenicia also increase caution and prevent the entry of materials that are not production related, but may find their way somehow to the raw material mixture. 
This is precisely why a soft drink can, whose aluminum compound contains the molecule, is not allowed into the plant!

Want to learn more about glass?

Contact us and we will be happy to meet with you.

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