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So I was happily painting some nice blended power weapons on some Sanguinary Guard I'm doing for a commission. Reasonably happy with how the blends looked, I stepped away. When I came back though, they looked like this:


What the hell happened? It's cold in my room, and when I've left spray painted things out in the cold similar things happened. However, this was only on the yellow part of the blend - the more subtle red blend looks absolutely fine.

I've had a similar problem with an old pot of GW Golden Yellow, is that what you were using? I assumed it was something to do with the age of the paint and just stopped using that colour. So far no cracks have occurred in my recent yellow paint jobs.

Cold causes it to contract, even if very slightly. what I reckon happened was you painted in a warm room, and then changed them over to the much colder room, the rapid temperature change causes the molecules to contract, and the paint to crack. (now not so sure bit) One reason why it was just the yellow was that it has a different molecular structure, however subtle, causing it to be different to the colours, which made it crack.

Then again I could be completely wrong

GW Yellow is dodgy. Beware.

Where you using flow improver? I heard this can be caused by using too much of it.

winnertakesall wrote:Cold causes it to contract, even if very slightly. what I reckon happened was you painted in a warm room, and then changed them over to the much colder room, the rapid temperature change causes the molecules to contract, and the paint to crack. (now not so sure bit) One reason why it was just the yellow was that it has a different molecular structure, however subtle, causing it to be different to the colours, which made it crack.

Then again I could be completely wrong

The cracking is also only on the tip of the thin blade where the metal cools the quickest and has the hardest time conducting heat\cool to the rest of the model.




I have had cracking issues when I have under coated a model in Bond Promoter and then painted a base color over it before it was completely dry.

I have seen a similar effect when varnished over not properly dry varnish.

The solvent in the new varnish slightly dissolves the not yet set previous coat, and it redries with cracks.

Perhaps try adding some acrylic polymer to your paint when thinning? Let it all dry more slowly, so the all blends are still fairly wet when you finish.

I was using more water in my paint than usual, as it was a blend. And yes, this was an old pot of GW yellow - Sunburst Yellow, actually! However, I've never had the same problems with my Iron Warriors, who have the requisite yellow caution stripes.

It could be to do with paint thickness- as in, how much of it is layered up on the model. I had some old Warp Spiders with blended carapaces, and on one of them I did a lot more layers than the others, without giving the previous layers enough time to fully dry. That one ended up with similar looking cracks to your power weapon.

If that is the cause, I would recommend taking it slower. Worked for me, but then, I'm still not 100% what caused the cracking.

The thing is, I've done other blends like this at much faster speeds, just with whites, greens, and so forth. I've come to the conclusion that it's a combination of cold weather and temperamental old yellow paint.