Spontaneous breaking of thermally toughened safety glass in facades: can we state if the Heat Soak Test (HST) was done according to EN14179-1:2005 or not ?

Spontaneous glass breakage of thermally toughened glass due to NiS inclusions can be largely prevented by a Heat Soak Test (HST). This well-established test has been incorporated into the European standard EN 14179-1:2005. However, according to literature (Yousfi et al., Verre 16(1):38–54, 2010b), there might be a theoretical probability, that a potentially dangerous inclusion could lead to a breakage after a well-conducted HST. Glass processors may neglect to conduct the test for a variety of reasons (sometimes furnaces are not calibrated, are overloaded, a wrong temperature profile is run etc.), even advising not to perform it at all, preferring to replace the glass should failure on a building occur. In this paper, we will show that, due to recent advances in microanalysis techniques, it is now possible to state after a failure on a building whether the heat soak test was correctly conducted according the EN standard or not.