Tried with various paints I had handy
Rust-Oleum crystal clear Enamel - Laser vaporized some of it, but no amount of repeats would get the last bit off the copper and it wouldn't etch.
Home Depot brand? Interior/Exterior Royal Blue fast dry spray paint - Lasers right off. Or looks like it does. Still leaves an etch proof invisible film on the board. Kind of pretty. Might make for good plaques and signs. :)
Krylon brand black paint pen - Laser barely did anything. I turned it up until it started burning but couldn't get a clean etc.
Acrylic "Ceramcoat" black paint - Didn't preserve details and dissolves in etch.
Green Sharpie - no discernible etching with laser
Black Sharpie - could see etching but not get all the marker off
blue painters tape - Oh, wow. Why didn't I try this first!?
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