A technique for laser engraving glass is to laser glass using an 80% screen. Instead of making your graphics 100% black, tell your laser that the graphics are 80% black or extremely dark gray.
If you were to use a microscope, you would see that there is a fine dot pattern as opposed to a solid marking. Remember, the problem with glass fracturing is due to the heat. By using a 75 to 90% screen, the glass is not heated as much and hence, does not fracture. You are left with a smooth pattern with minimal shards of glass.
—Richard Korbyl, Columbia Awards