Tips and Tricks for Glass Engraving

With a CO₂ laser engraver, you can laser engrave flat materials such as window glass or mirrors, round workpieces such as wine or champagne glasses, and conical items like bottles.
Cheaper, cast glasses are a good choice because they generally have lower lead content and are more homogeneous structure. Expensive, hand-blown glasses or crystal glasses may have stresses in the material that are aggravated by the heat during laser engraving, which may cause the glass to fracture.

You can also laser process mirror glass with a fiber laser by removing only the reflective layer on the back so that the glass itself is not engraved by the fiber laser, causing the surface to remain smooth.

The Trotec Speedy flexx has both a CO₂ and a fiber laser source. Thus, you can easily combine both processing options with a single laser machine.

There are a number of methods for laser engraving glass and creating special effects. Here are few:

1. Moist paper towel

Using a moist paper towel helps prevent the engraving area from becoming rough, and leads to a clear, white engraving result.
Before you start engraving, apply a moist single-layer paper towel to the glass. Make sure there are no air bubbles or overlaps. This would affect the engraved image. Then switch the Air Assist to OFF to avoid premature drying of the paper during engraving. After engraving, the residue easily wipes off, also cleaning the  engraving area is cleaned.

2. Application tape

In addition to moist paper towels, application tape can also be used to prevent the surface from roughening. With application tape, however, the engraving color is rather grayish and not bright white.
As with the paper towel method, make sure that no air bubbles and overlaps are formed when you apply the tape. After engraving, clean the glass to remove any adhesive residue.

3. Engraving without auxiliary materials

Moist paper towel or application tape are not required for processing glass. You can create effects by making adjustments such as changing the color in the graphic from 100% black to about 70% gray to minimize the effect of heat on large surface, to optimize engraving results. You can also go to the print settings, select the rasterization type “Ordered Dithering," but keep the same parameters. This change causes not quite as much heat to enter the material; hence, the surface is roughened less.

Glasses with curves can be processed with the rotary engraving attachment. For detailed instructions, see Tips and Tricks Rotary Attachment.

Glasses with handles are also processed using the rotary engraving attachment. It is important to make sure that the glasses are accurately placed so that the handle is not rotated into the engraving field. First, move the Y axis (rotary motion) to the very top. Clamp the workpiece so that the handle is slightly above the laser beam. Since the workpiece is rotated backwards for the laser process, there is no risk of collision with the laser head. For all workpieces with handles, make sure that circumference of the glass is large enough to accommodate the length of the graphic. Otherwise the graphic will be placed too close to the handle. You can easily check the position in the JobControl® laser software by using the “What you see is what you get” function. (WYSIWYG)

You can see the exact position of your graphics in the JobControl® laser software, by using the “What you see is what you get” function (WYSIWYG) and the crosshairs. If you are using the crosshairs, simply move the Y axis in the target position for lasering. Then place the job on the plate to the crosshairs. By moving the Y axis again, you can check the dimension of the job on your workpiece and correct any faulty positions of the workpiece or the job.

For photo engraving on glass, use grayscale matrix of 70% black. This causes less heat to be applied to the glass, and the result will be finer. We recommend using an average resolution of 500 dpi and using the rasterization type “Ordered Dithering." This optimizes the image data for the material.