Pilkington Plc

Ian Heaton Smith

Ashley Carl Torr

Stanley Lythgoe

John M Bradshaw

A glass composition capable of being chemically strengthened by ion-exchange within 100 hours to provide a glass with a surface compressive stress of greater then 400 MPa and an ion-exchange depth greater then 200 microns comprising: SiO 58% to 70% (by weight), Al O 5% to 15%, Na O 12% to 18%, K O 0.1% to 5%, MgO 4% to 10%, CaO 0% to 1% with the provisos that the total of the Al O and MgO is in excess of 13%, the total of the amounts of Al O plus MgO divided by the amount of K O is at least 3 and that the sum of the amounts of Na O, K O and MgO is at least 22%.

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St. Helens, United Kingdom

Ian Heaton Smith