Crystal engraving remains a delicate operation that requires more than ten years of experience to master all its dimensions. There are three techniques for decorating cold glass. The most precise, diamond point engraving, is performed with a simple metal stylus finished with a diamond chip. Wheel engraving is an old technique, practised by engravers of fine stones. It is done with an electric lathe, copper, lead or cork wheels and abrasive powder. Finally, the last technique is to send a pressurised sand, the corundum, a very hard and abrasive rock, onto the object to be engraved.