Sand blasting is usually the best method to create high-contrasting, frosty engravings onto glass. When sandblasting is not available, a high quality mark can still be created on a glass surface by simply using a CO2 laser engraver. When laser engraving glass, the traditional sense of engraving away material is not what usually works best for this material. The best way to create contrasting quality marks on the glass is to utilize the laser beam to create micro fractures in the glass just below the surface. The trick is to do this without also damaging the surface of the glass.
In order to get bright engraving results on a glass surface, it is best to first apply a masking to the glass surface. There are several options to use for masking. Often a wet paper towel or newspaper creates the best results and can simply be laid onto the glass and engraved on. A small bit of dish soap can also be applied to the towel or newspaper as well to further enhance the effect of the masking. The newspaper or towel will be engraved, allowing the heat of the laser beam to micro-fracture the glass just underneath the surface, leaving a high quality crystalized mark on the glass.
Here are some suggestions and tips for creating the best possible engraving results on glass:
- Cheaper (price and quality) glass works better for lasering than expensive glass.
- Use a 2” or 2.5” focal length lens (1.5” or less is not very good for this kind of work).
- On a 60W laser, consider starter settings of: 30% power, 80% speed, 600 DPI resolution.
- In the artwork setup, set the fill color of the text/graphics to be 70% RGB black (not 100% black like what is traditionally used for engraving).
- If dithering or "rendering" options are available in the laser settings, these can be adjusted to fine-tune the quality and look of the engraving.
- On curved surfaces, focus the laser beam to be close but just off-center of the highest point of the glass curvature. For areas further out from the center, try to run these sections of the artwork in a separate pass, where the laser can first be refocused on those further outlying areas (away from the center/highest point of the curvature). Be careful not to go too far out, as the focal length of the laser lens has limits as to how far away the focus point can be before it is too weak to make a mark.
- Consider using a micromesh sanding pad to wipe down the engraved areas after lasering. 8,000-10,000 grit sanding pads should work well for this. Pads like this may be found on wood working websites such as rockler.com.