Help solve a cracked paint mystery

I’m working on an F-104 and yesterday sprayed the nose in two colors (both Polly Scale acrylic paints) over a primer of Tamiya black that I applied a week ago. One color, the green, came out well, but when I sprayed the gray, it cracked (rather spectacularly, as you can actually see the black primer underneath). I sprayed the same gray Polly S paint on the wings without a problem a few days ago, thinning it both times with Testors acrylic thinner (which Testors specifies as the correct thinner for Polly S acrylics). Does anyone know what could have caused the paint to crack so badly? And who only on the model itself (if you look at the overspray on the masking materials, the paint laid down beautifully there)?

I’m going to sand the gray off and respray the nose, but wanted to know if anyone knows what went wrong so I can avoid it moving forward.

Looks like a contamination issue, spray the paint on something that does not matter and see if you get the same result

Thanks! I’ll test it out to see how it works.

Looks like crakel paint was used. I am sure it wasn’t but that’s the effect.

:laughing: Yeah, definitely not what I intended!

If you do identify exactly how that happened please could you re-post those photos & the explanation on the Diorama forum, I know several guys who’d kill to get that effect on some semi-ruined walls – including me :tumbler_glass:

I’ve had paint crack when I’ve thinned it to much

I feel your pain, suffered the same frustration and here is what I learned from it:

I tossed everything vallejo in the dustbin, reserve all acrylics for painting details and mainly (95%) stick to enamel and only two brands: Humbrol; tested for decades and with excellent quality despite the pesky cans, and alclad II for metal and enamel again.

Each bottle of acryl, when empty is replaced by Humbrol.

The consequence: no more “reaction” between different paints, no more trouble with incompatible thinners, and I know how to use these brands as I use them all the time.

And yes, I use a paint mask while airbrushing and I do ventilate the room.

Finally, I give it at least a week drying time before spraying a second coat.

I forgot to post that I figured out what went wrong–apparently this bottle of Polly Scale didn’t like it when I thinned it a little too much. Once I stripped the paint, re-primed, and resprayed with slightly thicker paint (and using very thin coats) it laid down quite nicely. Lesson learned: 15+ year old Polly Scale paints can be temperamental.

Very good that you figured it out :slight_smile: but I’ll stay with my Humbrol addiciton. Bottles of 30+ years old, after some shaking and stirring work as if they were fresh from the shop.