Glass Foils “Burglars”

Press, Volume CVI, Issue 31110, 13 July 1966, Page 8

Glass Foils “Burglars”

Two men, armed with a crowbar and a brick, tried for five minutes to break through a 6ft by 3ft sheet of glass—and failed. They were taking part in a demonstration of “bandit” glass given before those attending the annual meeting of the Canterbnry-Westland branch of the Jewellers’ Aasociation. The meeting was attended by 33 delegates, and the demonstration by about 50 persons. After the New Zealand representative of Pilkington Brothers, Ltd., of Britain (Mr R. Robinson), had spoken about the "bandit” glass, be invited two delegates to the meeting to attempt to break through a framed sheet of It Mr K. Morrison, wearing a plastic visor and heavy canvas gloves, hurled a brick at the glass: it starred the sheet and bounced off. He then attacked the pane with a crowbar, starring and bulging it, but failing to break through. Mr R. Hornsby then attacked the glass with a crowbar, but his efforts also were

in vain. The sheet starred and cracked and glass splinters flew, but the ,060 in plastic interlayer held firm.

Mr Robinson said that in Europe and Britain the problem of smash-and-grab raids had in recent years become serious, and in some shops owners had resorted to “hanging screens”: sheets of 3-Bin toughened glass hanging behind the normal plate-glass window. This, however, was not entirely successful, and brought considerable problems in window cleaning. He demonstrated that while toughened glass would not break when a IJlb steel ball was dropped on it from a considerable height, or when it was struck with a hammer, a tap with 8 centre-punch could break it

The “bandit” glass, which was new to New Zealand but was in increasingly wide use overseas, comprised two Bin sheets of plate glass with a vinyl plastic interlayer, the three sheets being welded together under heat and pressure. The secret of its strength was the interlayer: the plastic could stretch up to 300 per cent When the demonstration sheet of glass was struck the glass itself broke, but most of it adhered to the inter-

layer. The interlayer then stretched and absorbed the force when the sheet was struck again, and eventually, as Mr Robinson said, it was . . like hitting a string bag.” After the demonstration Mr Robinson answered questions. Those present included Detective-Sergeant E. J. Stackhouse, crime-prevention officer with the Christchurch C. 1.8.