Posted By John M Donaldson I wonder if anyone can help with this? I am trying to determine the grade of glass in several of our premises. There does not appear to be any kite mark, B.S. or other identification mark so does anyone know of a piece of kit that tests the hardness of glass (without destroying it of course!)? Many thanks.

Posted By Alan Woodage John I had a similar situation with a construction dispute, from memory we employed pilkingtons to carry out a survey and ascertain if the glass was ordinary plate or toughened. this was done with a device that in essence tapped the glass with a metal hammer and then measured the resultant sound wave. In summary there is a piece of kit that will do it but what it is called I can't remember. I would suggest contact the technicl department of glass manufactureres or as suggested your local uni / college if they have a suitable materials lab.

Posted By Eric Burt John Sharples Stress Engineers Ltd, Unit 331, Walton Summit Centre, Bamber Bridge, Preston PR5 8AR. Tel: 01772 323359 They sell a glass identification kit which comprises a device for identifying toughened glass ( by looking at the stress patterns in the glass) and a laminated glass identifier. The whole thing comes in a kit and is excellent. I have used it many times over the past 15 years for doing glazing assessments. Laminated glass may not have any identfying marks on it so the only test is the one used in the kit (apart from breaking it!) Toughened glass normally has some type of marking in the corner. I've got a kit so if you want to take a look at it before you buy give me a call. Regards, Eric