Hairline Cracks !!

[ericmaxman]

Guys, I seem to have an emergency here. A few of my kits have hairline cracks on them. Especially those silver ones. Here is a shot.

[MrObsessive]

Ouch!!

What kind of paint/clear did you use?

The clearcoat dries faster than the color coats--------because the previous coats are still shrinking this can lead to the cracks in the topcoat/clearcoat.

I ran into this problem years ago with Tamiya Acrylics, using their clearcoat over their water based acrylic colors ALWAYS led to cracking about a month or so down the road!

[ericmaxman]

I'm using some sort of automotive clear. I thought it would of higher quality, and so it seems I may be wrong. So the key is to give is more time to cure?

[MrObsessive]

I'm using some sort of automotive clear. I thought it would of higher quality, and so it seems I may be wrong. So the key is to give is more time to cure?

Okay-------Most likely that is a hot acrylic enamel/lacquer clear. Lacquers don't like to be sprayed over anything else but other lacquers. But you can spray acrylic enamels clears over lacquer because they aren't so hot. Likewise hobby enamel clears can be sprayed over just about anything.

But it seems that reaction should have been immediate------how long ago did you paint the car?

Might be the only solution would be to take the car apart, strip it, then repaint.

[ericmaxman]

Okay-------Most likely that is a hot acrylic enamel/lacquer clear. Lacquers don't like to be sprayed over anything else but other lacquers. But you can spray acrylic enamels clears over lacquer because they aren't so hot. Likewise hobby enamel clears can be sprayed over just about anything.

But it seems that reaction should have been immediate------how long ago did you paint the car?

Might be the only solution would be to take the car apart, strip it, then repaint.

Car was completed some time in May. It is not too visible under direct sunlight, but when up close, it hurts to see it crack like that. Even my Magnum and Mustang has those crack lines.

[george 53]

WoW E-Man, I have NEVER seen a clearcoat crack THAT BAD!!! Make sure your paints are compatable with each other.Like Bill jus said NEVER spray laquers over ANYTHING but laquers. I hate to echo Bill, but he's right, the only fix for that I'm afraid, is the ol Purple pond. What a shame! the car looks pretty nice.

[ericmaxman]

WoW E-Man, I have NEVER seen a clearcoat crack THAT BAD!!! Make sure your paints are compatable with each other.Like Bill jus said NEVER spray laquers over ANYTHING but laquers. I hate to echo Bill, but he's right, the only fix for that I'm afraid, is the ol Purple pond. What a shame! the car looks pretty nice.

The worst part is that it seems to be spreading like an epidermic. And I did go through quite a hassle trying to get the car to look right. Removing the paint is indeed a painful procedure.

[ericmaxman]

Guys, the culprits.

http://www.dpiaerosol.com/aerosol5.htm

http://www.dpiaerosol.com/aerosol3.htm

[george 53]

Well E-Man, the first stuff(the clear, I think) says it's an acrylic, so I don't really see anything there that mighta caused the cracking, BUT, the Color paint says its some kind of modified resin. Maybe it needed more time to gass out? You'd think that with both paints beein by the same manufacturer they would be compatable. Who knows Bro, at least you now know NOT to try it again. I still think the pond is the only solition. Maybe one of the guys might be able to answer the compatability question.

[Brendan]

Two things that come to mind. When you put the color coat down, did you spray the entire kit inside and out? Also with the clear, did you spray inside and out? I've had this happen with acrylic lacquers and cellulose-based paint. If you don't paint the entire kit, you have different rates of shrinkage on the kit. If you don't paint the inside of the car and just painted the outside, the paint can pull the body in different directions. Most manufacturers tell you to paint the whole kit in the base coat to make sure it doesn't do this...also the clear as well.

The other thing that comes to mind is what primer did you use? If the primer is not suitable to the paint, this will happen. Hope this helps.

[Olle F]

You'd think that with both paints beein by the same manufacturer they would be compatable. Who knows Bro, at least you now know NOT to try it again. I still think the pond is the only solition. Maybe one of the guys might be able to answer the compatability question.

It's not enough to use different paint types from the same manufacturer, unless they clearly say that they are indeed compatible. For example, Testors have enamels, acrylics and lacquers, but that doesn't mean that you can use, let's say a laquer clearcoat on an enamel basecoat. The other way around might work just fine though, and there are some types of paints that are compatible, but there's really no guarantee that it will work. It's kind of a hit-or-miss deal, and after several paint fiascos in the past, I have come to the conclusion that the only fool proof way to a good paintjob is to use paint of the same type and (just to be safe) from the same manufacturer. I might be overly cautious, but at least it gives me peace of mind.

[CAL]

The worst part is that it seems to be spreading like an epidermic. And I did go through quite a hassle trying to get the car to look right. Removing the paint is indeed a painful procedure. :rolleyes:

Yeah, it's done.... I am afraid.

Your base and clear are drying and shrinking at different rates. It doesn't look like a gas-out problem.

Paint systems today are getting very specific and you don't want to mix and match base/clear, plus there are all kinds of variants depending temp, moisture, flash-time, when it comes to pick out the right clear.

who knows what is in that junk.

[ericmaxman]

Two things that come to mind. When you put the color coat down, did you spray the entire kit inside and out? Also with the clear, did you spray inside and out? I've had this happen with acrylic lacquers and cellulose-based paint. If you don't paint the entire kit, you have different rates of shrinkage on the kit. If you don't paint the inside of the car and just painted the outside, the paint can pull the body in different directions. Most manufacturers tell you to paint the whole kit in the base coat to make sure it doesn't do this...also the clear as well.

The other thing that comes to mind is what primer did you use? If the primer is not suitable to the paint, this will happen. Hope this helps.

I don't quite get it when you said inside out. Do you literally mean from the inside to the outside or something else? I usually do 2-3 mist coats and 3-4 heavy coats. Same goes for the clear.

As for the primer, I used the primer from the same manufacturer.

[ericmaxman]

Well E-Man, the first stuff(the clear, I think) says it's an acrylic, so I don't really see anything there that mighta caused the cracking, BUT, the Color paint says its some kind of modified resin. Maybe it needed more time to gass out? You'd think that with both paints beein by the same manufacturer they would be compatable. Who knows Bro, at least you now know NOT to try it again. I still think the pond is the only solition. Maybe one of the guys might be able to answer the compatability question.

For my silver cars, I used the automotive paints. And so I was wondering, if I used the modified resin based paint, is it safe to coat with with the automotive clear?

[ericmaxman]

It's not enough to use different paint types from the same manufacturer, unless they clearly say that they are indeed compatible. For example, Testors have enamels, acrylics and lacquers, but that doesn't mean that you can use, let's say a laquer clearcoat on an enamel basecoat. The other way around might work just fine though, and there are some types of paints that are compatible, but there's really no guarantee that it will work. It's kind of a hit-or-miss deal, and after several paint fiascos in the past, I have come to the conclusion that the only fool proof way to a good paintjob is to use paint of the same type and (just to be safe) from the same manufacturer. I might be overly cautious, but at least it gives me peace of mind.

The problem is availability. Hobby paints here is mostly tied down to Tamiya only. Furthermore, they cost around USD $10, which is quite a lot of money. I did use the same silver and clear coat from the same manufacturer and series.

[ericmaxman]

Yeah, it's done.... I am afraid.

Your base and clear are drying and shrinking at different rates. It doesn't look like a gas-out problem.

Paint systems today are getting very specific and you don't want to mix and match base/clear, plus there are all kinds of variants depending temp, moisture, flash-time, when it comes to pick out the right clear.

who knows what is in that junk.

Could you explain more on the gas-out problem? I don't seem to understand that very well.

[Brendan]

I don't quite get it when you said inside out. Do you literally mean from the inside to the outside or something else? I usually do 2-3 mist coats and 3-4 heavy coats. Same goes for the clear.

As for the primer, I used the primer from the same manufacturer.

What I mean by inside and out, I mean to paint the inside of the body as well as the outside. A lot of people I know don't paint the insdie of the body trying to save paint.

[Brendan]

While I'm thinking about it, how are you storing your models? Are they getting hot and cold rapidly from like sunlight? I also remember reading somewhere that some metallics don't like having clear over the top. I don't remember which magazine...some automotive magazine.

[ericmaxman]

While I'm thinking about it, how are you storing your models? Are they getting hot and cold rapidly from like sunlight? I also remember reading somewhere that some metallics don't like having clear over the top. I don't remember which magazine...some automotive magazine.

I keep them in a cupboard. Away from the sunlight. I will have to do some more research on which paint does not like clear coats over them.

[Brendan]

Could you explain more on the gas-out problem? I don't seem to understand that very well.

What he means by gas-out (off gassing) is the rate of the solvent and propellant releasing from the paint in a gas state, which is the paint drying. If you put paint on too soon, the gas would try to exit and would get caught by the second layer of paint and cause adhesion problems. It usually looks like small air bubbles in the paint.

[ericmaxman]

What he means by gas-out (off gassing) is the rate of the solvent and propellant releasing from the paint in a gas state, which is the paint drying. If you put paint on too soon, the gas would try to exit and would get caught by the second layer of paint and cause adhesion problems. It usually looks like small air bubbles in the paint.

So can I safely assume that the paint did not react, but simple the cooling period was too short?

[CAL]

So can I safely assume that the paint did not react, but simple the cooling period was too short?

Not necessarily, it would be safe to assume that it's not a gas-out issue.

A hot clear still could react with fully cured base, soften it up, and you still end up with the same problem. Not as likely, but could still happen.

[Brendan]

I think your best bet is to not use it on your metallic painted cars. You might want to find a different clear coat. The only other thing I can think of is if you want to use that clear do put on only one to two coats.

Has it happened to any of your other non-metallic painted kits?

[ericmaxman]

I think your best bet is to not use it on your metallic painted cars. You might want to find a different clear coat. The only other thing I can think of is if you want to use that clear do put on only one to two coats.

Has it happened to any of your other non-metallic painted kits?

I don't quite think so. My Fujimi Megane seems okay. I have 3 models that I did not clear coat and regretted that.

[Zoom Zoom]

Some people have experienced this with Tamiya clear over Tamiya paint, if applied at the wrong time. If a base coat and clear coat don't chemically meld, if they're different enough and cure at a different rate this kind of thing can happen. I had it happen in the 80's with Tamiya acrylic clear and transparent colors, they looked great when shot but they shrank so much as they dried they cracked so badly the bodies looked like the bottom of a dry lake bed.

I do a lot of decanting/airbrushing these days, including Tamiya, and I add Tamiya clear into the last couple coats of Tamiya color so that I don't have any potential problems.

The metallic silver was probably not completely cured and/or the clearcoat didn't match chemically so it cracked as it shrank and dried. One of those things that might not happen all the time. Try to stick with one system/brand if possible; use a clear that's designed for the base coat. Even that's not always the answer if the clear was applied in the wrong window of time.