Paint Problem

[qquake2k]

I'm working on my Executioner. I painted the entire rocket with automotive primer and then black enamel. I waited 24 hours, then masked it and sprayed it with the primer again. What could have caused this wrinkling? I've never had that happen before.

 

[ONAWHIM]

The effect looks somewhat uneven. Is it possible there was something on the airframe?

 

[Pat_B]

Assuming your primer and paint were compatible, I'd guess that the primer still wasn't completely cured. It was still contracting when you painted your topcoat over it and it broke up the topcoat as it shrunk. The cracks look to be the largest in between the fins. That's an area that tends to trap a lot of paint when it is being sprayed due to the vertical fin surfaces directing it back towards the body tube. It's likely to be an area that gets thick with primer to begin with.

 

[ONAWHIM]

Exploring this further, were there temperature fluctuations while drying?
Also did you apply too heavy?

Reading more closely I see you painted primer over enamel.

 

[qquake2k]

The weather was breezy, overcast, and about 65 degrees. I've painted in these conditions before with no problems. I was painting primer over the black, because I wanted the blue to be lighter. I've done that before too, painted primer over enamel, then painted a different color of enamel over the primer.

 

[bguffer]

Can primer be laquer based?
https://forums.gideontech.com/index...86ba0704a6f7a&topic=32026.msg339791#msg339791

Bob

 

[jdud]

Was the primer a lacquer? I use Duplicolor automotive primer, which is a lacquer. My understanding is that you can safely apply an enamel over a lacquer, but vice versa causes the problems you have encountered. Also, enamel paints can take several days to fully cure (even under prime weather conditions). Anyhow, it looks like you have some sanding in your future. Been there, done that!

 

[mkadams001]

I think your undercoat was not completely dry when you applied the primer. Notice that it did not crack on the tape but only on the previously painted surface. Your paint job may have alligatored even if you used an enamel over the paint.

 

[blackjack2564]

You have not mentioned what brand using.

Most of the new enamels must be re-coated in less than 1hr or after 48-72 hrs.

Having had the same problem you did. I just figure it will take me a week to paint any multi-color scheme. Give 3 days between colors.

I don't take chances after getting all the way down to a few stripes, then ruining the entire rocket due to a few wrinkled stripes. Starting over made me long for the "old" days of trouble free paint.

 

[qquake2k]

Well, I sanded the bad spots as best I could, wiped it down with rubbing alcohol, and painted on the blue. It turned out surprisingly good. If you get close to it, you can see some imperfections. But over all it's not bad at all.

 

[MarkII]

I have gotten the very same crackling that you got on a few occasions with primer applied on a bare rocket, In every case, they showed up in the fin area, usually over the fillets but once or twice on the fins themselves or on the tube in between. There was no consistent sequence of events or conditions that produced it as far as I could tell. I just sanded them out and repeated the coat, which always solved the problem. But what Pat_B said makes perfect sense. I think that sometimes I go a little heavy on the first coat of primer (because I sand that coat down anyway), and sometimes I also go over the first coat again before it has completely dried if I think it needs better coverage. But in my case, I have only seen it with white primer, never with the high-build automotive primers that I also use. I think that Pat has nailed the cause, at least in my cases of it.

Mark K.

 

[dedleytedley]

To avoid paint problems I look at the first aid info on the spray bombs. This will show the solvents used in the paint. Those which contain strong solvents,e.g. acetone, toluene(lacquers) will often attack paints with weaker solvents, e.g. xylene, petroleum derivatives(enamels). Since I've avoided mixing these different paints I haven't had any paint difficulties. Clearcoats are often lacquer based and can crinkle your beautiful finish if you apply it over enamels or if it's put on thickly over lacquers. Thicker areas of the underlying paint are more likely to fail as are plastic nosecones if left unsanded. Applying thick coats of paint can cause problems as the surface of the topcoat skins the solvent can go into the substrate instead of escaping into the air. An old painter showed me a furniture stripping technique using paint thinner. He laid rags over the piece, soaked them with solvent, then wrapped the entire piece with thick poly sealing it completely with duct tape. Two days later almost all of the finish had crinkled and wiped off with the rags! The key is the penetration of the solvent. Ted

 

[plano-doug]

I'm working on my Executioner. I painted the entire rocket with automotive primer and then black enamel. I waited 24 hours, then masked it and sprayed it with the primer again. What could have caused this wrinkling? I've never had that happen before.

Most fast-drying (ie, automotive) primers are lacquer based. They are compatible with enamel paints, but only unidirectionally - you can put enamel over lacquer, but not the other way around, which is what you did when you put primer atop the black. Not sure why you would do that.

Normally, if you want to add another coat - ie, a different color - over the black, you let the black cure for a few days - maybe a week - scuff it up with your favorite fine sand paper (320, 400, 600 - whatever you prefer) then shoot it with more enamel. The cured, sanded black will function just fine as a primer for the next color.

If you must primer over the enamel, you will need to build up a few thin coats with some sanding in between to avoid cracking.

HTH.

Doug

.

 

[Scotty Dog]

You have not mentioned what brand using.

Most of the new enamels must be re-coated in less than 1hr or after 48-72 hrs.

Having had the same problem you did. I just figure it will take me a week to paint any multi-color scheme. Give 3 days between colors.

I don't take chances after getting all the way down to a few stripes, then ruining the entire rocket due to a few wrinkled stripes. Starting over made me long for the "old" days of trouble free paint.

Oh, how rite you are.The good old days. I been scratching my head on these new paints for some time now. I put on a first coat on some fins this weekend . I ran down town for about 1-2 hrs. Came back and applied second coat and It WRINKLed.The worst part is ,I would have bet it was going to happen. I knew better and did it anyways I ran into this issue with the new paints last year when I painted my garden tractor. I painted it so it looked like the M&MS car. (Nascar) I ran out of paint during the project. Next day, maybe 14-16 hrs later I went and finished the paint job. Well, every place I painted over what was already painted-Yup-it wrinkled. Talk about being TEED-OFF!!! I ended up useing a good primer-SEALER over it and let that set for DAYS. Then repainted and all was good. I hate rework Scotty Dog

 

[GRIFFIN]

Well, I sanded the bad spots as best I could, wiped it down with rubbing alcohol, and painted on the blue. It turned out surprisingly good. If you get close to it, you can see some imperfections. But over all it's not bad at all.

Looks Awesome!!

 

[MarkII]

I was no better at spray-painting back in the Good Old Days than I am now. Actually, I did considerably worse back then. Now I'm enjoying my Mediocre Current Days. Hey, it's an improvement. I'm not mourning the end of the Bad Old Days. (Bad for me, anyway.)

Mark K.