I did some quick tests with titanium. Not sure of the exact alloy this one is as I got some from a friend of a friend, but it looks promising I did 3 tries of my grey scale map to see how they’d do.
Starting with the lightest on the far right where I used minimum power and maximum speed which was way too light, I tried increasing power for the second one and then I reduced speed as well for the third which really started to look good. The interesting thing about titanium is that you don’t need to coat it in anything to mark it like this. For other metals you’d need a metal marking compound on them, but this was just putting the metal in the Glowforge and “etching” on it. The most curious part to me is the 100% in the top left corner. Really the text tags and that top block were all 100% black in the bitmap, but the square turned out blue while the text is black.
It’s probably related to how much area the heat is being applied to in a certain amount of time, but I’m sure it’d be interesting to use this somehow to do multi color prints.