Toughened glass may not be all that it's cracked up to be

Effectiveness of toughened glassware in terms of reducing injury in bars: a randomised controlled trial 2000;6:36-40

Toughened glassware, used to minimise the risk of injury in bars, may not be all that it's cracked up to be. And there is an urgent need for it to conform to recognised standards, finds research in Injury Prevention.

Bars and pubs in the UK have largely switched from the normal (annealed) glassware to the hardened variety. This happened in 1993 after research showed that toughened glass was harder to break, and that when it did, it tended to form small cubes-similar to those seen when a toughened windscreen is damaged-rather than jagged shards.

A random sample of 57 bars and pubs, including over 1200 bar staff, across England and Wales took part in the study. The complete stock of Nonic-straight-sided pint glasses with the bulbous rim-was replaced with either the toughened or annealed variety. Bar staff were asked to record the numbers of injuries they sustained as a result of handling the glasses over a period of six months.

The results showed that the injury rate among bar staff using the toughened glasses was 60 per cent higher than among those using annealed glasses. The severity of the injuries was the same in both groups. But unlike the annealed glasses, the toughened ones tended to break spontaneously while on the shelf, and bar staff using these tended to sustain several injuries at once on different parts of their bodies as they cleared away the fragments. It had been assumed that spontaneous disintegration only occurred in old, worn glasses, but the findings show that, according to the bar staff this also occurred in brand new glasses.

An impact resistance test showed that more energy was required to break the annealed glass than the toughened glass, explaining, in part, the higher rate of injuries among staff using the hardened glassware.

Many of the staff questioned either expected the toughened glass to be completely ubreakable, or that it would be harmless when broken. These attitudes may make staff rather more careless when handling these glasses, so increasing the potential for injury, say the authors. Nevertheless, "quality standards are urgently needed to ensure that toughened glass products are what they claim to be," they conclude.

Contact:

Professor Jonathan Shepherd, Violence Research Group, Department of Oral Surgery, Medicine, and Pathology, University of Wales College of Medicine, Cardiff.