Paint problem

[ferrarijoe]

need some help. Started working on Fujimi's Aventador model. I bought some Scale Finishes Lambo blue for it. The paint looks all funny kind of like when plastic dose not blend togther during molding process. The body is molded in white. I started with 3 coats of Tamiya light Gray primer, then 4 coats of The lambo blue. the paint came out smooth, but look all wrong. It was around 60 degrees and 30% percent humidity when i sprayed it. I use 25 psi with my iwata airbrush. How can i fix it and stop it from happening again, do i need to send it to the purple pond and strip it. thanks for the help.

[ferrarijoe]

[Quick GMC]

i use Tamiya primer and Scale Finishes. The only time I have experienced this texture, including Zero paint, Scale Finishes and a couple others, is when the paint was drying too fast, before it hit the model.

I am by no means someone who should be giving paint advice, but I have been through quite a bit with airbrush painting to get where I am today. To fix this problem when I had it, I adjusted the PSI by sound/feel instead of looking at the gauge, opened up the paint flow a bit more and held the airbrush closer to the model. I was spraying too far away, my PSI and paint flow weren't in the right ratio, so I was getting a sandy texture because the paint was too dry when it hit the model. This will not allow the paint to flow into the cracks and crevices like I see in your model.

Scale Finishes base coats dry very quickly, so you need to adjust accordingly.

Also, another thing' If you paint too soon after the Tamiya has time to set, so it can go through and craze the plastic. I have experienced this with Zero paint lacquers, but not Scale Finishes.

Edited April 5, 2015 by Quick GMC

[ferrarijoe]

The funny thing is it doesn't have a rough texture to it. It's all smooth. In the pic the hood looks all grainy but it's smooth. Could I just respaint with a lower psi over this or do I need to strip it. I was worried it was the primer. I let the parts dry overnight before color coats. It dropped to the 30s overnight. I'm paint out in my work shed right now. And its not temp controlled, but was 70 when I sprayed primer.

Edited April 5, 2015 by ferrarijoe

[maltsr]

I've had this happen several times, and I almost exclusively use Tamiya paint. The paint seems to 'orientate' itself with the swirl marks in the raw plastic. Not sure of a solution, but i have tried these two methods with varying degrees of success:

1) Try building up the paint in mist coats. This sometimes solves the problem, but beware heavy clear coats afterwards.

2) Strip the paint from a smaller part, and sand the raw pastic with fine sandpaper. Repeat the painting process (light coats) and see if this works. If it does, the good news is you have solved the problem - bad news, you have to repeat on all the other parts .

Good luck

[Ace-Garageguy]

The patterns, or "swirls" (the lines that indicate where the plastic hesitated flowing during mold-filling) in the surface are a dead giveaway that there's crazing of the plastic itself going on under the primer. If the primer is not a sufficient barrier, you shoot the color on the "wet" side, and the solvent in the paint is on the "hot" side, you'll get this effect...especially these days as manufacturers continue to experiment with cheaper and cheaper grades of polystyrene that is increasingly LESS solvent resistant.

If this were my own model, I'd be madder than hell, because both your paint products SHOULD be entirely compatible with Fujimi's plastic.

If there is indeed crazing of the plastic, as it appears to me to be 100% the case, stripping will only uncover bare crazed plastic.

If this were my own model, I'd try building up lightish coats of color over what's already there, with plenty of flash time in between. You may be able to fill the crazing, sand it all slick, and apply a wet flow coat over the top as usual.

Notice this identical appearance, and the line on the door. Dead giveaway. (This model, not mine, is on the Drastic Plastics board, and is said to have been painted with Scale Finishes too. No mention of what primer, if any, was used. It's a Monogram model, and some of their and Revell's kits are VERY sensitive to solvents too these days.)

Edited April 5, 2015 by Ace-Garageguy

[ferrarijoe]

So in the future should I put more coats of primer on? I've never had this issue before. I have scalefinishes primer on the way also, and wonder if it would be better to use their primer with their paint.

[Ace-Garageguy]

So in the future should I put more coats of primer on? I've never had this issue before. I have scalefinishes primer on the way also, and wonder if it would be better to use their primer with their paint.

Sadly, I think that this is a question only experimentation will answer. If the Scale Finishes paint is hotter than what Tamiya's primer will block, and if Scale Finishes primer has been formulated to deal with this specific issue, then...yes.

Lotsa ifs in there.

You may have to modify your color application process, shooting very light coats (which I try to avoid because of the potential for getting grainy orange-peel).

[StevenGuthmiller]

This looks to me like a problem I had a couple of times when I was spraying MCW lacquers over Testors lacquer primers. The surface is smooth, but it's almost as if you can see the primer through the paint. kind of a white blotchy background in spots. I finally attributed it to incompatible primer & paint. It seemed as if the paint was too hot for the primer & was "dissolving" the primer, & drawing it up to the surface. The answer for me was to use several coats of Duplicolor primer over the Testors. The Duplicolor primer is more "impervious" to the lacquer paint.

I've only used Tamiya primer a couple of times, & personally, I wasn't really impressed, especially for the price. Just my opinion.

Steve

Edited April 6, 2015 by StevenGuthmiller

[fseva]

The funny thing is it doesn't have a rough texture to it. It's all smooth. In the pic the hood looks all grainy but it's smooth. Could I just respaint with a lower psi over this or do I need to strip it. I was worried it was the primer. I let the parts dry overnight before color coats. It dropped to the 30s overnight. I'm paint out in my work shed right now. And its not temp controlled, but was 70 when I sprayed primer.

I have had that problem with SF - it seems as if the metal particles want to collect at the surface, giving you a "frosty" look!

I personally think that this happens when you try to get full coverage by applying too much paint all within a few minutes time. If you give it several mist coats, and then wait a while between the mist coats and a couple of heavier coats to get full coverage, that should do the trick - just don't apply one really heavy coat at the end. I emailed the owner of SF (Jameston Kroon) and we had a long discussion about what causes this and how to correct it, but he admitted he was at a loss to give any definite cure.

I was so disappointed with SF metallics giving me the frosty look, and having to sand it all down and start over, that I have gone back to the old standby hobby lacquers - I never had this problem with them.

Edited April 7, 2015 by fseva

[Art Anderson]

Bill Engwer: The patterns, or "swirls" (the lines that indicate where the plastic hesitated flowing during mold-filling) in the surface are a dead giveaway that there'scrazing of the plastic itself going on under the primer. If the primer is not a sufficient barrier, you shoot the color on the "wet" side, and the solvent in the paint is on the "hot" side, you'll get this effect...especially these days as manufacturers continue to experiment with cheaper and cheaper grades of polystyrene that is increasingly LESS solvent resistant.

I've been airbrushing model cars with automotive lacquers for a good 50 years now, and have a pretty standard technique I use every time. First, bear in mind that while Scale Finishes paints started out being acrylic enamels (which don't craze plastic, BTW), their modern "base coat/clear coat" car colors are lacquers, and lacquers do take some special handling. And no, it's not something that just cropped up more recently with "cheaper plastics"--that was a huge problem to overcome back in the 60's when AMT, etc. model car kits were being molded in a very hard styrene grade.

First, on plastic bodies, I use automotive lacquer primer, and have done so exclusively from the very start of my process decades ago. I thin the stuff to the consistency of 2% milk (done by eyeball, not some set formula, BTW--just by observing how the thinned primer--and finish color--"sheets" down the sides of my airbrush color jar). Then, I use what I call TSC, meaning "Thin, Soft, and Close" with the airbrush. Properly thinned automotive primer won't cover quickly, rather it takes numerous passes with the airbrush to get full primer coverage. By "Soft", I mean as low a pressure in my airbrush as will spray the primer or paint. By "Close" I mean moving my airbrush in close to the surface, generally an inch or so away.

Now, when I primer a body shell, I watch very closely. Even very light coats of primer will at least "frost" the surface of the model car body slightly--you can actually see that, but it's a form of "crazing" that is so miniscule that it disappears with each succeeding pass (now on model car kits made in Japan, they tend to use a rather hard styrene blend, which will be subject to frosting much worse than say, the softer styrene blends used by many other manufacturers, so greater care is a requirement here, but it can be done). Lacquer thinners, even the so-called "non-penetrating" thinners will penetrate styrene plastic to some extent. The crazing (even the minute frosting I mentioned above) happens when the solvent releases the locked in stress in injection molded styrene, which causes that "swirled effect" seen in Joe's pics above. So what to do?

This is where primer comes into its own on a model car body, in my experience. The solids in the primer will fill fairly tiny crazing/frosting, and the primer can actually be polished out before color coats, and almost always the primer tends to "shock proof" the plastic surface, in my observations over the years.

Lacquer primers do not need to have a rough surface in order for the color coats to adhere--all lacquers tend to penetrate preceeding coats of lacquer to at least some extent, so I "wet sand" my primed body shells with 5600 to 6000 grit polishing cloths, which gives me a satin finished primer surface. Then, I use exactly the same "TSC" approach to my color coats--often even to the point of the last passes (particularly with metallics) being thinned even more than when I started.

This system works for me, and has for so long that I cannot even use a rattle can anymore--lost my touch with those years ago.

Art

[ferrarijoe]

Art you say use automotive lacquer primer. I ordered sf primer is that equal to it? Or do I need another kind. And if so what brand do you guys use? I hope sf primer is good after spending $75 plus on sf paint I don't want to have to throw a bunch of money on primer. I need to figure something out. And with automotive lacquer primer do I have to get reducer and hardner with it. I am dumb when it comes to automotive paints. I do have alclad primer anyone have knowledge on how good it is. I bought it on accident thinking it was their glosscoat for their chrome. I have used it on a tank but put acrylic over it.

Also if I go automotive primer route can I spray tamiya rattle can over it. Just want to know for future use, since I have tons of it.

And is the automotive primer safe on resin.

Thanks for alll the help.

Edited April 6, 2015 by ferrarijoe

[Art Anderson]

Art you say use automotive lacquer primer. I ordered sf primer is that equal to it? Or do I need another kind. And if so what brand do you guys use? I hope sf primer is good after spending $75 plus on sf paint I don't want to have to throw a bunch of money on primer. I need to figure something out. And with automotive lacquer primer do I have to get reducer and hardner with it. I am dumb when it comes to automotive paints. I do have alclad primer anyone have knowledge on how good it is. I bought it on accident thinking it was their glosscoat for their chrome. I have used it on a tank but put acrylic over it.

Also if I go automotive primer route can I spray tamiya rattle can over it. Just want to know for future use, since I have tons of it.

And is the automotive primer safe on resin.

Thanks for alll the help.

Well, if you have Scale Finishes primer, I'd go ahead with that. As for spraying other kinds of paint over automotive lacquer primers, I've done that more times than I can count. And yes, automotive primers work quite well on resin bodies.

Art

[Ace-Garageguy]

And no, it's not something that just cropped up more recently with "cheaper plastics"--that was a huge problem to overcome back in the 60's when AMT, etc. model car kits were being molded in a very hard styrene grade.

.Art

NOTE: I'm not arguing with Art here. He has years of valuable first-hand experience with this stuff he's willing to freely share. But...

In my own experience, which is what I based my statement on, many of the older models are very solvent resistant. I shot SEM self-etching primer (really hot, for real cars) wet, on a Johan '61 Dodge, and it laid out slick and as pretty as you please, zero crazing. Excellent adhesion too, as I determined from subsequent light filling and feather-edging. Same thing on a first-issue Revell Challenger One, about '62/3 vintage. The other older kits I recall using it on, like early-issue white AMT '29 Fords, behave the same way. No crazing, excellent adhesion. But the softer more recent gray ones though...forget about it.

Both a 10-year old Monogram '70 Chevelle and a recent Revell '50 Olds both crazed so badly, I was forced to dechrome them and build "shaved" customs, as there was no saving the delicate raised detail.

Though I agree with Art for the most part about using automotive lacquer primers as a barrier coat (I use Duplicolor's rattle-can line for the most part), even these are plenty hot enough to craze Revell's '50 Olds if shot wet, which I like to do to get a nice non-orange-peeled surface that requires very little sanding.

[Ace-Garageguy]

Art you say use automotive lacquer primer. I ordered sf primer is that equal to it? Or do I need another kind. And if so what brand do you guys use? I hope sf primer is good after spending $75 plus on sf paint I don't want to have to throw a bunch of money on primer. I need to figure something out. And with automotive lacquer primer do I have to get reducer and hardner with it. I am dumb when it comes to automotive paints. I do have alclad primer anyone have knowledge on how good it is. I bought it on accident thinking it was their glosscoat for their chrome. I have used it on a tank but put acrylic over it.

Also if I go automotive primer route can I spray tamiya rattle can over it. Just want to know for future use, since I have tons of it.

And is the automotive primer safe on resin.

Thanks for alll the help.

Automotive "lacquer primer" is a single-component product, no hardener, and you thin it with straight lacquer thinner from the hardware store. There ARE various additives available for 1:1 use, like agents that slow the flash time to reduce blushing, etc....but these generally make the material "hotter" and more likely to damage model car styrene.

You can also get excellent results using more complex two-part catalyzed primers. They are available as urethanes, epoxies and polyesters. Once cured, any of them are pretty much impervious to anything you might use as a model car topcoat. BUT...they tend to be fairly high-build products, and will quickly obscure fine detail if hammered on. On the other hand, they can save a TON of time (is "ton" a valid unit of time-measuring?) if you do heavy bodywork and modifications. In the scales we work in, they are essentially self-leveling, sprayable bondo, which is a pretty cool option.

Just FYI, this is a 2-component catalyzed urethane primer, shot with a full-scale gun, on a body I'd done VERY heavy mods to. You see how thick the stuff looks, but it certainly has its uses.

[Art Anderson]

And yet, I used MCW's lacquer primer on my '50 Olds body with no problems whatsoever (They use DuPont lacquers I believe). Oh well, huh?

Art

[Ace-Garageguy]

And yet, I used MCW's lacquer primer on my '50 Olds body with no problems whatsoever (They use DuPont lacquers I believe). Oh well, huh?

Art

That's certainly good to know. I'll have to try it, because I've been holding off on building some models until I had the crazing problem licked.

Once again, that's the real value of this forum. One guy's experience may be different from another guy's. but the free sharing of information gathered from actual experience can save many of us a lot of disappointment, and time burned up experimenting instead of building.

Edited April 6, 2015 by Ace-Garageguy

[ferrarijoe]

Yah I don't do a lot of body mods. I'm more of a box build guy why some photo etch and decal add-ons. I just wanted more color options only reason for trying new paints. Will have to pick up some dupilcolor next time I go out. What brand should I look for to airbrush it instead of rattle can. And do I have to get it at a automotive paint store?

[Ace-Garageguy]

Yah I don't do a lot of body mods. I'm more of a box build guy why some photo etch and decal add-ons. I just wanted more color options only reason for trying new paints. Will have to pick up some dupilcolor next time I go out. What brand should I look for to airbrush it instead of rattle can. And do I have to get it at a automotive paint store?

If Art has had good results using the MCW primer on what I consider to be the overly-sensitive Revell '50 Olds plastic, if I were you, I'd try that.

But first, try the Scale Finishes primer you already have coming. It just might solve the entire problem.

Edited April 6, 2015 by Ace-Garageguy

[fseva]

And yet, I used MCW's lacquer primer on my '50 Olds body with no problems whatsoever (They use DuPont lacquers I believe).

Hmmm... I think he sells PPG...

[fseva]

The crazing (even the minute frosting I mentioned above) happens when the solvent releases the locked in stress in injection molded styrene, which causes that "swirled effect" seen in Joe's pics above.

I'm not so sure... I've seen these patterns in the bare plastic - they always seem to be in the same general area, namely the middle of the doors. Of course, if you start a new kit by sanding the body, you will greatly reduce these deforms, and I don't think they will show up again (in the paint)... Take a look at the raw plastic before sanding - you have to hold it at a certain angle to the light to see these deforms in the plastic...

[fseva]

Art you say use automotive lacquer primer. I ordered sf primer is that equal to it? Or do I need another kind. And if so what brand do you guys use? I hope sf primer is good after spending $75 plus on sf paint I don't want to have to throw a bunch of money on primer.

Sorry to say, I was very disappointed with SF primer - its way too thin, and requires so many passes just to get it to be opaque, that you'd be better off with a $5 can of Model Master gray or white lacquer, which is what I use again, after the SF primer proved so poor in coverage. The biggest problem for me was that with all those passes, how many of the beautifully engraved details are being filled up with primer?!

[fseva]

I have also used Duplicolor BPR0031 Scratch Filler Primer available from Amazon at...

http://www.amazon.com/gp/product/B00407RTBW/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Use right out of the can! An 8oz can is a ver reasonable $7 plus change!

[StevenGuthmiller]

Sorry to say, I was very disappointed with SF primer - its way too thin, and requires so many passes just to get it to be opaque, that you'd be better off with a $5 can of Model Master gray or white lacquer, which is what I use again, after the SF primer proved so poor in coverage. The biggest problem for me was that with all those passes, how many of the beautifully engraved details are being filled up with primer?!

On occasion, I use a combination of Testors & Duplicolor "sandable" primer. The Testors covers really well but also doesn't seem to level as well & can have a tendency to go on too heavy & obscure detail if too many coats are applied. The Duplicolor is thinner & levels better, but it's hotter & will craze if applied too heavily. I really don't trust the Testors alone to act as a barrier with Automotive lacquers, (I've had issues with it in the past) so I shoot a coat or 2 of the Testors to get good coverage & then several coats of Duplicolor to give a good barrier for the lacquer. Works pretty well.

Steve

[fseva]

On occasion, I use a combination of Testors & Duplicolor "sandable" primer. The Testors covers really well but also doesn't seem to level as well & can have a tendency to go on too heavy & obscure detail if too many coats are applied. The Duplicolor is thinner & levels better, but it's hotter & will craze if applied too heavily. I really don't trust the Testors alone to act as a barrier with Automotive lacquers, (I've had issues with it in the past) so I shoot a coat or 2 of the Testors to get good coverage & then several coats of Duplicolor to give a good barrier for the lacquer. Works pretty well.

Sounds like you've got all the bases covered!