"Crazed" aluminum paint?

[DynaSoar]

I was finishing a bird with aluminum finish Rustoleum over gloss white Rustoleum (over white primer over urethane over sanding sealer) and a strange thing happened. Over some parts of the bird, especially the fins but some body and a little nose, the paint crinkled like it had been a foam of bubbles that had all popped, leaving a crazed pattern of adjoining raised ridges. It didn't happen over the whole bird (some parts came out beautiful) so it's not a mismatch in paints.

Is this due to some areas not being as dry as others? It had all seemed dry to the touch, but perhaps under the surface it still carried some solvent.

How best to recover from this? I've been sanding it* and getting the wrinkles off, but that leaves a patterns of cracks that you can feel. Should this be sanded all the way down, or filled? Should I reprimer it? I'm assuming the aluminum paint can't be sued to fill with, as it shrank so much that even where the finish is good, it got into the body wrapping spiral and made it show, even tough it had been filled with filler even prior to all the other layers and had been smooth.

* I sing the praises here of drywall sanding sponge: it fits wonderfully in between the fins and conforms to the body. If I need more grit than the fine sponge, I can wrap it with medium and have a flexible sanding block. Plus, it has just enough give to keep me from breaking off a fin as I sand off this grrrrr fricka fracka aluminum ~!@#$%^& {NO CARRIER}

 

[hokkyokusei]

I've had that recently. I was wondering if it was temperature related?

 

[DynaSoar]

Originally posted by hokkyokusei
I've had that recently. I was wondering if it was temperature related?

I was painting in fairly cold air (maybe 45 F). But the paint and the bird had been inside (~70 F) until just a few minutes before. This happened almost instantly.

I'm more convinced now that the layer under it wasn't dry everywhere. Gloss enamel doesn't dry as fast as primer.

Does aluminum go better over gloss or primer?

 

[hokkyokusei]

I was painting in a relativley cold basement. I warmed the paint can, but not the rocket, As you say, the 'crazing' effect was almost instant.

It way well be as you say though. I often try to get another coat on asap. So the first may not have been dry.

It's not the end of the world though, I've found that a rub down with 600 grit paper and another coat generally fixes it.

 

[Stones]

Originally posted by DynaSoar
...
I'm more convinced now that the layer under it wasn't dry everywhere. Gloss enamel doesn't dry as fast as primer.
Does aluminum go better over gloss or primer?

More than likely, this is the case. The underpaint needs to be all the way dry. I usually paint only over primer, meaning I don't paint a base coat and then other colors on top of the base. I mask off the primer areas so that only one color is painted in each section, over the primer. So far, so good.

 

[DynaSoar]

Originally posted by Stones
More than likely, this is the case. The underpaint needs to be all the way dry. I usually paint only over primer, meaning I don't paint a base coat and then other colors on top of the base. I mask off the primer areas so that only one color is painted in each section, over the primer. So far, so good.

I tested it, and this was in fact the case. I sanded off the crazed stuff and waited a day, then repainted. No problems.

I found a spot that still had some bad finish underneath making it rough, and was going to resand and repait, so I tested it again while the paint was still tacky. Instant crazing.

 

[sandman]

DynaSoar,

I gave this tip before and "honestly" it can be taken as Gospel!

If you can smell paint...IT'S NOT DRY YET!!

Yes, I learned that one the hard way too!

sandman

 

[DynaSoar]

Originally posted by sandman
DynaSoar,

I gave this tip before and "honestly" it can be taken as Gospel!

If you can smell paint...IT'S NOT DRY YET!!

Yes, I learned that one the hard way too!

sandman

I'm sure I could have located your earlier warnings, and probably those of others too. But us scientists have a saying, "It's an empirical question", which often means "Well yeah, but let's see what happens if...". Sometimes there's just no telling us anything, but then we'll go around telling everybody what we figured out.

Actually, this time there was no smell. I suspect the extra solvent was trapped just below the surface by the glossy coat. Smoother coat, less surface area, slower evaporation, da?