Paint problem leaves me scratching my head

[924_CarreraGTS]

I have been working on a '69 Firebird model. I painted the body with Plastikote sandable primer, sanded w/ 2000 grit, airbrushed a mix of Testors enamels, and, when that was thoroughly dry, applied Testors clear laquer gloss overcoat from the spray can. The last coat of clear was applied in cold (40 degree) weather, but only briefly--I had sprayed about 4 coats before that in warm weather. Night had fallen, and the temps had dropped, but I needed one more coat, so I took the model outside, one part at a time, sprayed quickly, and brought it back in.

About two weeks later, I started polishing with Micromesh 3200 grit cloths. All went well (except for some burn-through), but on one panel, the clear peeled away in little balls like glue. Irritated, I left the model alone (polished with 3200 grit) and resprayed the clear in warm temps a few days later. One month later (last night), I tried polishing again, this time applying strips of masking tape to the edges to avoid burn-through. I polished everything out, and when I went to remove the tape, the clear coat all peeled off like dead skin.

What is the problem? I have used this painting method many times with success, so I know it's not a chemical incompatibility. Is it:
1. The cold weather spray (I heard that doing it quickly, like I did, works)
2. The fact that I applied clear over a partly polished surface (reducing adhesion)
or 3. The tape (I've done that before, too.)

Please help so I don't repeat this infuriating stunt once I get all the paint stripped and reapplied.

Alex

[Some_Kid]

Even though you've used the painting method before, it could have been the fact that you used lacquer over enamel, which can work but sometimes it doesnt.

[MPWR]

Originally Posted by 924_CarreraGTS

so I know it's not a chemical incompatibility.

Wrong in one.

Don't ever assume laquer is compatable over enamel. Sure, you can get lucky and have it work occasionally, but sooner or later it will certainly bite you in the ass. Sounds like it just took a chunk out now....

Honestly with as long as Testors enamels take to outgas, I'd be anxious overcoating them with anything at all.

[rsxse240]

I'd venture to say that it has to do with the surface being to smooth and not sticking. I had the same problem when painting a hyabusa. I used testors enamel gold as a base, then stoplight red metallic. once they both were dry, the clear went on. keep in mind I didn't scuff either color coats as they were metallic, and doing so would have destroyed the shimmer, which is why I painted the red over a fresh (still sticky) gold.

anyhoo, I went to pull the mask off after doing another color overlay for pinstripes, which came out quite nicely, the clear had peeled away from the red, and pulled some of the pin striped paint with it.

keep in mind, I used all enamel, but I feel the situation is quite similar even though the difference in paint bases.

I resolved this by stripping the model with easy off, and then dot 3 and started over. this time I used gold base followed by red then silver for the pin stripes, THEN the clear. I still had a few smaller masks to do after the clear but since I painted all colors within about 6-8 hours they all gassed out nicely, and did not separate.

I don't suggest putting laquer over enamel when it's still wet, unless you thin your enamel with laquer thinner which usually makes it to hot to paint, giving unwanted surface irregularities.

I hope this helps clear things up.

[cyberkid]

http://www.tamiya.com/english/scale/beginner2/2.htm (bottom of the page)
Use this as a basic guide for paint layering. Even though the brands are different the strategy is always the same. I'd say you were lucky before. I wouldn't even attempt to clear enamel with lacquer unless it had been drying in my dehydrator for a least 1 year, that's right 1 YEAR.

[freakray]

Originally Posted by MPWR

Wrong in one.

Don't ever assume laquer is compatable over enamel. Sure, you can get lucky and have it work occasionally, but sooner or later it will certainly bite you in the ass. Sounds like it just took a chunk out now....

Honestly with as long as Testors enamels take to outgas, I'd be anxious overcoating them with anything at all.

Totally agree with you there, enamels and lacquers aren't compatible - some people assume they are just because they've gotten lucky and not seen a reaction previously.

[924_CarreraGTS]

Due to my troubles with Testors paint and compatibility, I've decided to switch my paint line over to Tamiya, which I've only heard good things about. A few questions:
1. Are all "X-" paints acrylic?
2. Are the lacquers safe for use on bare styrene plastic?
3. Is the famed TS-13 clear coat (lacquer) safe for use over acrylic?
4. What's the deal with the "polycarbonate" paint?

Thanks

Alex

[freakray]

Wow, all those questions could be answered with either a search or a visit to Tamiya's website

1. The 'X' ranges of paints are the bottles, there are both enamels and acrylics available in this range - they are differentiated by the bottle style - square bottles are enamels and round bottles are acrylics.
2. Yes, but priming with Tamiya primer is always better (See Car Modelling FAQ also)
3. No, don't use TS-13 over acrylics, Tamiya makes an acrylic clear for this use.
4. The polycarbonate range is made for use on polycarbonate bodies, also known as lexan which are otherwise known as radio control car bodies.

[Mr. Me.]

x - gloss colours, xf - flat

[cyberkid]

If you can get it, I would suggest you look into Gunze's bottled stuff too. Better choice and better quality.(At least IMHO)

Steve

[drunken monkey]

and why couldn't this have been continued in the other thread?

merged...