Cracking Paint?

[StevenGuthmiller]

Any body have problems with the Testors "wet look" clear cracking on them over a period of time? I've had the same issue on a pair of builds now in the past couple of months. I usually put a coat or 2 of clear over the color a day or so apart. then I let it dry for maybe a week, wet sand & then finish with one last coat of clear. Then I let it cure for at least 4 or 5 days, up to a week or 2, before polishing. The funny part is, the cracking doesn't begin to show up until later. This last build began to show minor cracking, just on the sides, after polishing. A full 2 or 3 weeks after putting on the last coat of paint! I polished the cracks out & it looked fine for a day or 2, & then the cracks begin to re-appear over a wider area than before! It has me completely baffled. especially since I have 2 projects moving along at the same time, painted at the same time with the same can of clear, & only one is cracking. It seems that I only have problems with it happening on non-metallic paint, but I'm not sure that has anything to do with it either as the paint on the roof is not cracking on this build, but the sides are & they're both the same color. I had been using Testors #28139 "Ultra Gloss Clearcoat" up until a recent switch to the wet look clear which seems to coincide with the cracking issue. I think at this point, I may dump the wet look clear for the time being & return to the ultra gloss. There's nothing more frustrating than having a seemingly perfect paint job fall apart on you weeks later like some sort of leprosy! Just thought I'd pick all your brains to see if any one had an answer. Steve

[Ace-Garageguy]

Well sir, I've seen your work, so you're obviously a competent modeler. I haven't had any problems (so far) with Testors wet-look clear shot over Testors metallics or basecoats, or Duplicolor colors. I always use Duplicolor or Plasticoat primers.

I HAVE had severe cracking issues on 1:1 cars when I shot urethane basecoat-clear over solid older paint (collision repair blends) that had previously been primered with a non-sanding enamel primer (which I didn't realize until I had to strip all the affected areas and start over from bare metal).

Have you changed the primer you're using recently, or could the manufacturer have possibly changed the formula? What about the color coats you're shooting the Testors clear over? Same as always??

[microwheel]

Have you changed the primer you're using recently, or could the manufacturer have possibly changed the formula? What about the color coats you're shooting the Testors clear over? Same as always??

That would be my question as well. I have used testors wet-look clear lacquer, myself, in the past, over testors spray can lacquer, and Tamiya's spray can paints which are pretty much a lacquer paint as well, with no issues. Every time I have used it, I had always primed with Tamiya's fine finish spray primer. And have never had a cracking issue. The only time I have had issues with cracking in paint, was when testing the wet-look clear over enamels or acrylics, or even over flat base colors (Tamiya's flat colors mostly, never really had any issues with testors clear coats over testors flat colors.) But I also saw it happen when I tried different types of cheap primers, mostly the hardware store brands. So to try to figure out why it is doing it now, depends alot on what your clearing over. And yes testors base colors are a little different formula than their metallic paints, so that could still be you issue. Also the humidity can have an effect on it as well at the time of painting.

[bobthehobbyguy]

Although I never had the problem I heard that Tamiya clear over Tamiya paint had an issue. You either had to clear right after the final color coat or what weeks before you cleared.

[High octane]

I've never had a problem with Tamiya or Testors Clear, and I always shoot the clear coats 24 hours after the color coats.

[StevenGuthmiller]

Well sir, I've seen your work, so you're obviously a competent modeler. I haven't had any problems (so far) with Testors wet-look clear shot over Testors metallics or basecoats, or Duplicolor colors. I always use Duplicolor or Plasticoat primers.

I HAVE had severe cracking issues on 1:1 cars when I shot urethane basecoat-clear over solid older paint (collision repair blends) that had previously been primered with a non-sanding enamel primer (which I didn't realize until I had to strip all the affected areas and start over from bare metal).

Have you changed the primer you're using recently, or could the manufacturer have possibly changed the formula? What about the color coats you're shooting the Testors clear over? Same as always??

Same primer as always. Duplicolor White or gray. For color coats, mostly MCW lacquers with a few Duplicolor here & there. Funny thing is, I've had this happen 3 times in the past few years. All 3 times with MCW non-metallic colors. First time was a couple of years ago with a '60 Merc hardtop. The body was a metallic gold & was fine, but I painted the top MCW light beige & the whole top cracked. Since then, no problems, metallic or non-metallic, until recently with a '60 Imperial with MCW Dawn Mauve paint, & now the Ford with the Geranium. Funny thing is, the top is painted Geranium as well with no sign of cracking, As well as the white area, which is painted with Duplicolor paint. The whole thing just has me completely stumped! Steve

[StevenGuthmiller]

I've never had a problem with Tamiya or Testors Clear, and I always shoot the clear coats 24 hours after the color coats.

That's pretty much my routine s well. I'll do several primer or color coats in one day, but I usually space out my clear coats 24 hours apart to allow some time to gas out & level off. I'm beginning to suspect the Testors lacquer primer that I use for the initial primer coat could be the culprit. I like to use it because it covers better than the duplicolor primer, especially the white, & it's not as hot. I've had problems with Duplicolor primer crazing the plastic when shot directly on the body. But, even then, if it was the priming system that I'm using, I would think it would happen more often. I just don't get why, even on the same body, It's so sporadic. Steve

[microwheel]

. I'm beginning to suspect the Testors lacquer primer that I use for the initial primer coat could be the culprit. I like to use it because it covers better than the duplicolor primer, especially the white, & it's not as hot. I've had problems with Duplicolor primer crazing the plastic when shot directly on the body. But, even then, if it was the priming system that I'm using, I would think it would happen more often. I just don't get why, even on the same body, It's so sporadic. Steve

Hi again Steve, I think you might be on to something there with the testors primer. That's why I use Tamiya primer exclusively. I had way to many random issues with testors primers. I have yet to have any problems with Tamiya's lacquer primers. And about the only time I even use Duplicolor primer anymore is when I need a sandable primer during body work or modifications, and then, like you, I never use it directly on the bare plastic. When I have a model that doesn't need alot of body work, just before paint, I give it a couple of medium coats of Tamiya primer and it's ready for whatever paint I want to shoot over it, be it air brushed or spray cans, (though I don't use spay can paints very often anymore). One issue I had with testors lacquer primer in the past, was, it seems if you washed your model in a mild dish soap solution, just before painting, and any soap residue gets missed, not matter how little of it, the primer will tend to pull away from those areas, especially low spots and edges. But like I said, there was a lot of random issues with it for me, so I quit using it all together. For the guy who posted about using Tamiya clear coats over Tamiya paints. I have never had a issue with that. I have even used Tamiya's air bush acrylic clear over their spay can lacquer paints with no issue. As a matter of fact, I have even used Tamiya clear coat acrylic air brush paint over testors lacquers with no issues. I always thin Tamiya acrylics with denatured alcohol though. I have never used their clear lacquer though, mostly because their acrylic has always done the job for me when I use it. Right now I mostly use Model Masters enamels thinned 50/50 with hardware store lacquer thinner and shot through my air brush, (both their enamel paints and clear coat, shot through a air brush), when I need a color they don't have, I play around with mixing a few of their colors to get one I need. Using their paints mixed with lacquer thinner, usually makes it lay alot smoother and it quickens the drying time. Most of the time it's ready for a light sand and polish within a week.

[Snake45]

Right now I mostly use Model Masters enamels thinned 50/50 with hardware store lacquer thinner and shot through my air brush, (both their enamel paints and clear coat, shot through a air brush), when I need a color they don't have, I play around with mixing a few of their colors to get one I need. Using their paints mixed with lacquer thinner, usually makes it lay alot smoother and it quickens the drying time. Most of the time it's ready for a light sand and polish within a week.

Boy, it sounds like we could have been Separated At Birth. That's almost exactly my painting routine. Except I find I don't need to wait a week for LT-thinned MM enamels--they're ready to sand and/or polish in 48 hours, and usually within 24.

Here's a tip for you: Next time you're airbrushing MM enamel, try thinning it with naphtha (lighter fluid) instead of lac thinner. The stuff has a slower drying time than LT-thinned paint, which means it flows out better than LT with less pebbles/orange peel, but not so slow that it will have more problems with runs or sags than LT. It too is ready to work in 24-48 hours. I usually use naphtha now if I'm shooting a paint I don't want to clearcoat but polish out direct. With this stuff I find a very light polish will give me a very nice "factory" paint job.

There is one WARNING on using naphtha, though: Do not thin more paint than you're going to shoot in the immediate future. The stuff will turn to Jell-O within a week, sometimes in as little as 3 or 4 days. Once this happens it can't be brought back; the paint is history. (Lac thinner thinned enamel is good almost forever, as long as it's stored airtight. Just yesterday I shot some I know for a fact I thinned almost three years ago.)

[microwheel]

Thank Snake, the only reason I said about a week, cuz I usually get busy with assembly on other parts of the model and it takes me a week or so to get around to even messing with the body, so it may be ready sooner, but most of the time, I'm not ready for it lol.

And hey Steve, I may have something you can try to see if you can solve and save your cracking paint issue. At this point it cant hurt to try it, and it should work. If you've already got the wet-look clear wet sanded and polished, give it a luke warm bath. If you have access to a air brush, and can get your hands on a bottle of Tamiya's clear acrylic, mix a little of it,(3parts paint, to 2 parts denatured alcohol which you can get cheap at a hardware store), and give your entire body 1 mist coat- and a couple of medium coats of the Tamiya acrylic clear. It will dry enough for sanding and polishing within 24 hours. It should also fill in the cracked wet-look cleared areas if they aren't too bad. I have saved a few paint jobs that way in the past when I have had ones that gave me problems. This process worked for me over lacquer based clears in the past, I haven't really tried it over enamel based clears, mostly because they dry slower than the acrylic does. If you give the cracked areas the first few light coats of acrylic clear before doing a whole body spray, it should fill them in enough to smooth everything out when you go to do your final sand and polish. Like I said, at this point what do you have to loose. If it doesn't work, your no worse off than you are now, the most you'd be looking at is where you are at the moment with a strip down and repaint.

[StevenGuthmiller]

Thank Snake, the only reason I said about a week, cuz I usually get busy with assembly on other parts of the model and it takes me a week or so to get around to even messing with the body, so it may be ready sooner, but most of the time, I'm not ready for it lol.

And hey Steve, I may have something you can try to see if you can solve and save your cracking paint issue. At this point it cant hurt to try it, and it should work. If you've already got the wet-look clear wet sanded and polished, give it a luke warm bath. If you have access to a air brush, and can get your hands on a bottle of Tamiya's clear acrylic, mix a little of it,(3parts paint, to 2 parts denatured alcohol which you can get cheap at a hardware store), and give your entire body 1 mist coat- and a couple of medium coats of the Tamiya acrylic clear. It will dry enough for sanding and polishing within 24 hours. It should also fill in the cracked wet-look cleared areas if they aren't too bad. I have saved a few paint jobs that way in the past when I have had ones that gave me problems. This process worked for me over lacquer based clears in the past, I haven't really tried it over enamel based clears, mostly because they dry slower than the acrylic does. If you give the cracked areas the first few light coats of acrylic clear before doing a whole body spray, it should fill them in enough to smooth everything out when you go to do your final sand and polish. Like I said, at this point what do you have to loose. If it doesn't work, your no worse off than you are now, the most you'd be looking at is where you are at the moment with a strip down and repaint.

Thanks guys. The Tamiya primer issue is pretty much out of the question for me. No where to get it around here, & I really don't want to order it. I use too much primer to be ordering it on line all of the time. I'll have to try another avenue. As far as saving the paint jobs goes, I'm hoping that my habit of using 3 or 4 clear coats may save me on these. I pulled out the '60 Imperial last night after it "rested" in the box for a month or more. It had cracked even more than when I put it away. So I started re-sanding & polishing on a section of the hood & will now let it set for a few days & see if the shine "holds". Steve

[microwheel]

Steve, dont know if you have a Hobby Lobby anywhere near you, but they are starting to carry Tamiya's primer now. I bought some there just a couple of months ago. Check them out if there is one anywhere close by you and see if they have it.

Edited October 29, 2014 by microwheel

[StevenGuthmiller]

Steve, dont know if you have a Hobby Lobby anywhere near you, but they are starting to carry Tamiya's primer now. I bought some there just a couple of months ago. Check them out if there is one anywhere close by you and see if they have it.

I do. Up until now they've had only Testors, but I haven't bee there lately. Is the Tamiya a lacquer primer? I use almost exclusively automotive lacquers. Steve

[John Goschke]

Sorry to hear about this issue, Steve! The '59 Ford was looking really sharp.

I haven't had an issue with cracking clearcoats, either Tamiya or Testors "Wet Look."

When I have had issues with paint cracking it was from applying too much paint, too quickly or not waiting long enough before applying a second color over the first.

Is it possible that applying you're clear only 24 hours after the color coats is not giving the color enough time to dry thoroughly? Then as the clear coat dries the color underneath is still drying but at a different rate, leading to cracking in the surface finish?

[StevenGuthmiller]

Sorry to hear about this issue, Steve! The '59 Ford was looking really sharp.

I haven't had an issue with cracking clearcoats, either Tamiya or Testors "Wet Look."

When I have had issues with paint cracking it was from applying too much paint, too quickly or not waiting long enough before applying a second color over the first.

Is it possible that applying you're clear only 24 hours after the color coats is not giving the color enough time to dry thoroughly? Then as the clear coat dries the color underneath is still drying but at a different rate, leading to cracking in the surface finish?

That's possible John. I usually let my final color coat dry for a day or two before beginning clear coats. My only question on that theory is why it only happens once in a great while, & like in this instance, only on the sides? The roof, hood & trunk areas all look good. Plus the fact that it seems to happen so slowly over time. I guess I really don't know how long it takes the paint & clear coat to cure, but the last clear coat was applied on October 11th & the cracking didn't start to appear until around the 25th. That's 2 weeks! I sure thought the paint would have been done shrinking in a lot less time than that. But I do think you're right. Obviously one of the "under coats" is drying slower causing the top coats to crack. I'm just becoming of the belief that it's one of the clear coats rather than the color coats. The Testors clear definitely dries slower than the MCW paint. Steve

[microwheel]

I do. Up until now they've had only Testors, but I haven't bee there lately. Is the Tamiya a lacquer primer? I use almost exclusively automotive lacquers. Steve

Hi Steve, yes Tamiya's spray can primer is a lacquer based primer, and I've yet to find any type of paint that has issues with it. I use it exclusively. Yes a little more costly that other primers, but with the amount of time and money I put into my builds anyway, it's worth the extra cost to me to make sure I dont have issues with my paint jobs.

[StevenGuthmiller]

Hi Steve, yes Tamiya's spray can primer is a lacquer based primer, and I've yet to find any type of paint that has issues with it. I use it exclusively. Yes a little more costly that other primers, but with the amount of time and money I put into my builds anyway, it's worth the extra cost to me to make sure I dont have issues with my paint jobs.

Cost is not a major issue with me either. But availability is. I have to order almost all of my building supplies on line now because all of the hobby shops in my area are gone. Hobby Lobby is pretty much my only source for supplies locally. I'll check them next time I go in to see if they carry it. Could someone please put a bug in their ear & get them to start carrying BMF? Would be great if I could stop ordering that! Steve