Here is the scenario.
I like to take clear plexiglass, spray paint it [usually black].
Then I do an etching into it, spray clear coat on it, then paint the etching another color [usually white]. So far so good, but the problems start with the clear coat.
Why even spray clear coat, you might ask ? Reason is simple - The etch leaves the clear plexi looking foggy, not clear at all. Spraying clear coat on it makes it transparent again, ready to receive the contrasting color. So this step is necessary, not optional.
Problem is, spraying the clear coat on painted plexiglas often causes it to crackle badly, this posted example done today is extreme.
First pics shows when I sprayed some clear coat on the black before etch, it crackled just a bit. After the etching and another coat of clear, the crackles went wild, ruining the whole thing. Last pic shows what it looks like from the front, only a very few areas are unaffected, almost like a virus.
I have run into this before, I started doing these designs a couple years ago it happened to be in cold weather, when it happened I thought it was temp related.
Does it just the same in hot weather too though, sometimes even worse.
I have painted, etched/cut then clear coated 1,000's of other things made out of MDF, color core, metal, not once has this happened so it is unique to plexiglas.
Odd thing too, I have done the very same thing and sometimes it never happens, comes out perfect. Can't post examples as they are not forum friendly.
I doubt if anyone will have a solution as I doubt there are many who do this type of thing, just throwing it out there in case anyone could recommend a solution.
This peice here would have been jaw dropping and could easily have sold for $100 if not for the crackles, now it is scrap.