In this tutorial, we show you what to pay attention to when working with stone, and what to do to get good results.
Polished stone slabs or stones that have a very smooth surface will provide the best laser engraving results. For an optimal engraving result, the stone should have an optimally flat surface, so the final result is not distorted by curves.
Of course, you can also laser engrave “real” stones with a rounded surface. To this end, place the stone on a horizontal plane. Use a support for this, such as modeling clay. When focusing, use an average value of the area to be engraved, so the engraving becomes as uniform as possible.
We found small stones for jewelry, worry stones or similar types of stone in the tile departments of hardware stores. There you find mosaic tiles that are composed of small marble stones in many colours, or leveled river pebbles. Detach the glue on the backside and the net by placing the mat in warm soapy water. Thus, in no time, you get a variety of small stones that are clean, inexpensive, and suitable for laser processing.
Laser engraving stones produces stone dust, which can stick and cause stringing, depending on the type of stone. Therefore, check the nozzle opening before each engraving job (and even during an engraving job if it is a long job.) The nozzle can be clogged by the stone dust and block the path for the laser beam. By wiping with a cloth or rinsing the nozzle with water, you will restore the optimal performance of your Trotec laser. The functionality of the lens and the mirror should also be checked at intervals during stone engraving.
If you want to remove the natural dust layer of the stone or dirt, we recommend cleaning the stone before laser engraving. If you rinse the stone under running water only after the engraving, you may wash out a part of the stone dust from the engraving. However, this contributes to ensuring good contrast between stone surface and engraving.
Stones are natural materials and differ in their geological composition depending on the region. We will show you how to get good engraving results for your stones easily and quickly.
If you have a flat surface of at least 3×3 cm and sufficient test surface available, we recommend applying the grayscale matrix. Unlike for paper or wood, for most hard stone surfaces, you need full power at low engraving speed. As a starting value, we recommend 100% power (p) and about 30% speed (v) for a laser power of 60 watts, and 100% power and about 15% speed for less than 60 watts. If this setting does not yield results, reduce the speed and run the matrix again. The advantage of this method is that you can assign the exact power settings to each engraved field.
Using the grayscale gradient is efficient if the area available for testing is very limited. Draw a rectangle with a gradient from 100% black to white. The same printer driver and parameter settings can be used as for the grayscale matrix method. The suitable power setting can only be estimated with this method. If it is in the middle of the engraved area, the determined power value is 50%. The closer to the black area, the more power you have as a result for your setting.
The advantage of the grayscale gradient is that it can be applied even to very small areas.
Here is a list of stone types that are, in our experience, very well suited for laser engraving. The guiding values to achieve good engraving results were determined using a Speedy 360, 100 W -- and will also ultimately depend on your laser power, your specific stone and your graphics:
- Marble: p50%, v20%, 1000dpi, Z = -0.5mm
- Slate: p20%, v100%, 500dpi
- Concrete blocks: p100%, v20%, 500dpi
- Pebble stones: p80%, v30%, 500dpi, Z = +2
- Basalt: p12%, v50%, 500dpi, Z = -1
- Agate: p50%, v30%, 1000dpi, Z = +1.5
- Bricks: p100%, v30%, 500dpi, Z = +1.5
Bright granite stones are only suitable for laser engraving to a limited degree. You will have to inlay their engravings with color after the engraving process to get a high-contrast result. We explain below how this works.
Some types of stones lead to no or only poor results in laser engraving due to their composition. With a few extra tricks that we explain here, you can nevertheless get useful results from your stones.
A change in the Z-value can significantly improve the result of your engraving in many cases. The most striking thing is to try offset values of +1 mm and -1 mm and compare the results. For very hard stones, it may be better to choose a negative offset value, as this will allow more power to enter the engraving area.
Some stones yield no or only poor results when being engraved. By subsequently filling the engravings with acrylic paint (or similar type of paint), you can nevertheless ensure a high-contrast result. To do this, mask the surface to be engraved with an application tape, and engrave your desired motif. Then take acrylic paint and a bristle brush, and dab at the engraved areas with paint. Once the paint has dried thoroughly, you can peel off the tape and wash off the remaining, finer tape residue with water. The smoother or more finely polished, respectively, the surface of your stone is, the better the result will be after the filling. Porous or rough surfaces may cause the edges of your artwork to fray and not appear sharp.