When engraving glass, it is very easy for cracks to occur depending on the type of glass or on the lead content. Therefore, glass engraving must be done with care. The behavior may vary from piece to piece particularly with hand-blown glass. Coloration may be achieved by adding metals (cobalt, copper, magnesium, etc.), e.g. a blue coloration of the glass is achieved by adding cobalt. Cheap glass is often easier to engrave than crystal glass. The reason is found in the high content of lead which makes engraving with a laser beam more difficult.
When the laser beam hits the surface of the glass, the surface is heated and fine glass particles are blasted off. If the glass is unable to cool down, the craters arising become bigger and bigger and the engraving appears muddy.
For glass engraving, a double process may be recommendable. However, one should not engrave too often or the result will appear blurred. The result may be improved if the surface is moistened. To do this, wet newspaper is laid over the glass. It is also possible to wet it with washing up liquid. However, there is always a danger that the surface will dry out too quickly. Very good results may also be achieved by applying a protective foil (application tape). This procedure has proven to be the best tried and tested in the Trotec applications laboratory.
If deep glass engraving is absolutely necessary with the help of sandblasting, then it is very easy to produce an appropriate template using the laser. The best way is to stick the resist material directly onto the glass and trace the pattern using the laser. The workpiece may then be sandblasted very easily.
If you have to engrave domed glass, it is necessary to select a greater focal length, e.g. 2.5 inch. This makes the possible working area larger. Try to position the exact focus right in the middle. Then the areas outside the exact focal point will also be perfectly engraved.
For glass engraving, a laser pointer in conjunction with Trotec's AD-Logic software is particularly helpful for positioning. Align the working head precisely on a corner point or in the middle of the engraving area with the help of the laser pointer and the cursor keys. The engraving job may then be appropriately aligned on the red cross in the Manager.