I write this as an architect and forensic engineer. I have investigated glazing failures in Australia, Singapore, Malaysia, Thailand, Hong Kong, Macau, China, India (Mumbai), the UAE, Britain and Finland, some instances being the glazing of the Singapore Management University and the spontaneous fracture of glass in the walls and roof of the Eurostar Terminal at Waterloo.
In the course of an Internet search on the topic of “architectural glazing failures”, I came across several references to defects and the collapse of glass in the Chennai airport terminal in 2014 and 2015. For instance, an article in The Hindu (“ >Panels continue to break at Chennai airport ”, April 6, 2014) included a quote from a structural engineering expert at IIT Madras, who said, “There is no way that impurities alone crack a glass panel… is an engineering defect.” The quote from the IIT’s “expert” is alarmingly naïve. The phenomenon of spontaneous breakage of toughened (or tempered) glass, which is due wholly to gradual, temperature-related, phase change-related, volumetric expansion of near-microscopic impurities or inclusions of nickel sulphide (NiS), has been recognised in the glass manufacturing and processing industries in Europe, North America, Japan and elsewhere since the 1950s. I have publicly refuted the local glass industry’s habitual denial of nickel sulphide-induced fracture.
National standards organisations in several countries, including Canada, Singapore and Australia, have recently prohibited the use of toughened glass (unless laminated) overhead specifically to reduce the risk of injury due to collapse of toughened glass. It is now known that NiS-induced fractures can occur at any time between installation and as much as 40 years later. If toughened glass, and less often heat-strengthened glass, shatters into small cubic fragments (known as dice) and variously remains in place (at least temporarily) or falls, with no evidence of impact from a projectile or other extraneous object, a probable cause is nickel sulphide contamination of the glass. Not surprisingly, this explanation is rarely volunteered by glass manufacturers, suppliers and contractors.
Peter Hartog,
Bangkok, Thailand
