So, I was thinking… The difference between the polished rocks from Lowe’s and the unpolished rocks from Home Depot made a huge difference in contrast, and the lack of contrast was a big deal with the rocks in a pack of “painting stones” I bought to try out. Well, I’m not going to get a rock tumbler and spend weeks (and significant amounts of electricity and various polishing media) polishing them. On the other hand, perhaps I don’t need to polish them at all…
Well, since I happened to have the dregs of a can of spray lacquer handy (thanks to the Melrose cut-and-paste sign), I figured I’d give a set of rocks a spray on one side and leave the other side untouched, then engrave both sides on my fiber laser using the exact same settings, which I pulled from a previous rock job (3000mm/s, 70% of my 60W, interval 0.05mm, 80kHz, 200ns, 10 total passes).
Here’s one side of five arbitrarily chosen rocks, engraved without anything special. (The bottom right one I’d previously engraved, but I figured that would be good enough.)
And here’s the other side of the same five rocks, this time after a quick shot of spray lacquer (which I allowed to dry, of course – that stuff’s quite flammable).
So, the top right rock didn’t really improve – it may be better uncoated. The top left and the center both showed notable improvement, but they’re still not my favorite. (The center, especially, might be fun to paint black, engrave, and then lacquer to bring up the saturation.)
The bottom two rocks, on the other hand, were drastically better with a bit of spray lacquer to bring up the background saturation and therefore the contrast. I think I might have to spend some more time with this box of rocks.