- TLC1ST wrote:
- http://easttnforum.proboards.com/index.cgi?action=display&board=topics&thread=235&page=1
Tempered glass by it's very nature has a very high degree of stress in the sheet. On rare occasions there can be a weak point that can fracture. Temperature differential can bring increased stress to a higher stress point resulting in fracture at this small point in the sheet. When tempered glass fractures
it fractures into many very small dull edge pieces. Again this is a rare event.
It sounds like what you may have experienced is something known as "spontaneous breakage". Spontaneous breakage is a relatively well known (in the glass industry) - but somewhat rare - phenomenon associated with tempered safety glass.
One rather common cause of tempered spontaneous breakage is known as a "nickel-sulfide inclusion". In this scenario there was a very small chunk of metal (nickel-sulfide) that did not melt in the float furnace and that for whatever reason expanded or contracted and caused the glass to fail.
However, not all float lines produce glass with such inclusions - and some lines are relatively well-known for it. Who made the door? Different window/door companies buy their glass from different glass companies.
Another possibilty is that the tempered glass was damaged during the original installation in the door panel at the factory. Glass can sustain microscopic damage during handling that is not visible at the time. When glass is cracked, even very tiny - virtually invisible - cracks, the cracks will grow.
This growth can be extremely slow - literally tiny fractions of an inch per year - or slower. This growth can also be substantially faster as well. But in your case IF this break was caused by edge damage the crack that contributed to it was obviously a slow grower.
By its nature, tempered glass consists of an inner tension layer and an outer compression layer. If the inner tension layer is breached then the glass "explodes" into the 100's of tiny glass pieces that you found on your floor. So, this glass could have been damaged and it took a while for this crack to grow enough to penetrate the tension layer.
Tempered glass will not shatter from overheating - not the level of heat that you will experience in a "normal" situation anyway. Soda-lime (window) tempered glass will stay intact at temperatures exceeeding 500F degrees
unless the glass has a physical flaw as previously mentioned, which is why tempered glass is used in a typical oven door.
It is possible for a glass expert to sift thru all that rubble and determine the cause of the breakage, unfortunately very few companies warrant against it because while it is possible to determine a cause, folks rarely bother to do so unless there are other issues involved - injury or lawsuit for example.
So, since the cause isn't determined, it is "assumed" that the glass was shattered for reasons other than "spontaneous breakage".