Laser-engraved slate coasters:
Found these slate coasters locally…they were $7.99 for a stack of four with non-skid “feet” on the underside. Slate can engrave very inconsistently, depending on the source of the slate. This slate wasn't marked for its country of origin, so I risked the $8 and gave it a try…got lucky and they worked pretty well.
These take about 15 minutes to engrave a single coaster using the suggested max power settings marked on top of our laser (so we don't kill it prematurely). The time required per coaster should be much lower if several are placed side by side and all engraved together. A simple jig would simplify lining up multiple blanks…just mark (or cut out) a 4 inch square for each blank, center a copy of the artwork in each “location”. Make the squares one color (and set those to “Cut”…if you only want them marked, still use “Cut” but lower the power so it only marks the outline of the square).
After the locations are marked/cut, change the Cut setting's “Is Output” popup to “No” so you don't waste time on every batch of coasters trying to mark/cut those locations.
Make the logo you want to engrave a different color and set that to “Scan” mode. The settings I used for that part are 60% power, 65mm/s,and set the “Overstriking:” popup to “Rilievi” (or experiment with the other choices, I like that one best).
If the settings mentioned above don't make sense (or I didn't call out a setting you're curious about), here's an image of the settings dialog showing all the details:
When the engraving is done, there will be a fine layer of white powder covering that slate. They tend to look about like this:
The powder wipes off easily with a soft cloth, a wet cloth if you prefer, or wipe it on your jeans. Slate may have some inclusions that don't react consistently to the laser. If you enlarge the first photo, you can see a few of these adding “character” to the coaster. If you're buying a batch of blank coasters to run a for-hire job, it's worth considering adding some extras so you can reject any that have too much character…