Finally got my Lich King river rock done and the depth actually worked

I tried engraving a small piece of shale once, and it taught me a lot about how surface hardness affects the burn. The Lich King idea is cool, but I had even more trouble with the shadow work than the details. When I tried to make the Frostmourne look metallic, I found the power settings were fighting me. I used a cheap 12-watt tube laser setup, and trying to get a true burn without just charring the surface was tough. I ended up settling for a deeper engraving in the negative space which gives a nice contrast against the lighter rock. For stone, you have to account for the material's thermal mass. The slower speeds are less about the final look and more about letting the stone absorb the heat without immediately shattering. I usually run my tests on a scrap piece of slate first to see where the material tends to flake before committing to a nice piece of sandstone. My biggest mistake was trying to use too much power hoping it would cut through more easily. It just caused a messy, blown-out look that looked like scorch marks rather than intentional damage. It seems like you got lucky with the white vein blending in. On the other hand, I've had experiences where the rock acutally starts to glow a bright orange before the smoke comes out, and you know it's going to explode in chunks. If you start seeing that intense heat distortion right at the focus point, back off the power and just increase the travel speed instead. It keeps things under control.

I had my hands on a similar project using a different type of stone, a slate piece, and the biggest difference was definitly the pre-burn preparation. I used a simple water sprayer with a bit of dish soap to keep the surface cold right before I started any passes. It sounds basic, but it made a huge difference in how the heat transferred and prevented that glassy, peeling look you mentioned. If you don't keep the surface temprature down, the stone just seems to bake itself.

I usally work on a piece about four inches square so I can stand it up and run the laser over it in sections. For the finer lines, like the skull details, I found that reducing the power slightly and increasing the speed to around 15 inches per second gave me a much cleaner line than trying to brute force it with maximum setting. It took me three tries to get the right balance on my bench setup. I also noticed that the ambient humidity in the shop seemed to affect the burn quality, too. When it was humid, the smoke seemed thicker and the edges of the engraving were a bit softer. Definitely something to keep in mind if you're working in a garage. I ended up using a quick coat of matte black paint after the engraving was done, just to unify the color of the untouched rock sections and make the burnt areas really pop.

Did a memorial stone for a neighbor's dog last spring on a flat piece of granite and hit the opposite problem, the burn came out grey instead of dark no matter what I tried. Wiping it down with a damp rag between passes helped a bit, but what really made it pop was two thin coats of paint fill on the letters instead of one heavy one. Sounds like you landed on the same trick. For the dragon, I'd keep the scale edges on their own pass like you did with those cracks, layering reads way better than one deep burn.

I did a stag head on a chunk of flagstone last winter and the thing that saved the fine lines was a soft toothbrush and warm water after each pass. The burned powder settles back into the grooves and makes everythign look muddy, and I kept thinking my settings were off when really I just needed to scrub between runs. Also worth grabbing a few of the cheapest pavers from that same landscaping pile and testing on those first. Same quarry batch usually means the vein behavior is close enough to trust. If the zombie wins the vote, keep the ribs shallow, deep cuts on thin ridges flake fast.