Mythbuster--Red "Bleed"

[Muncie]

Looked like a can of worms, but this has been a good discussion.

Another variable is the paint.. the chemistry in modern paint products has a lot of variations - I don't understand it, but it's there.

back to the days of basics - enamel and lacquer and reference to the PPG repaint manual, 1976

Enamel dries by the evaporation of the solvents in the first stage and by oxidation of the binder in the second stage.  Reducer out, oxygen in.  Once oxidation has started, it's difficult for reducers in the top layers to get into the layers below

Lacquer dries by the evaporation of the volatiles - lacquer will remain more or less soluble. Lacquer thinner in one coat will soften/dissolve into the layer below.  If a top coat is applied heavy enough, the thinner will go through to the base material... in our case, (without a sealer) it can get into the plastic.

Some of the modern primers and paints that we use act are more like an enamel, some are like a lacquer, but most I've seen have characteristics of both.

Edited June 26, 2016 by Muncie

[Mike_G]

 

Has anyone considered the possibility that chemical reaction of some kind is actually creating the red tint? I ask because I've stripped white paint off white plastic using a white chemical (Easy-Off) and had some of the removed residue be a yellowish or tannish shade. Where's THAT coming from? While stripping with Easy-Off, I've also seen weird colors appear that had nothing to do with any paint on the body, or the plastic underneath. I can't give you a specific example, but I know I've seen this several times.

I think that's just the color of the EZ-Off itself as I see that every time I use it.

[RickRollerLT1]

With my Firebird paint problem I posted a while back, I tried every single trick in the book and the red was showing through the white. When I tried the duplicolor that got rid of it but crazed like a siv requiring a strip job.  I tired the Walmart gray primer followed by the white on a red molded hood like Snake did and it still showed through (tell me, how did you not get the pink cast showing through?).

The only thing that worked for me without crazing was Rustoluem Automotive primer SEALER. That covered the red without bleed through and allowed me to put the Wal-Mart gloss white on without a hitch as seen here (sorry for the kinda grainy pic, but you see the point).

So in a way, how opaque your primer is does matter but some can be way too hot on plastic as i've learned (the wal-mart gray also crazed the red hood i tested). I usually use the Sears/K-Mart primer as that gives good results but seems to be prone to bleed through no matter what. But now i know what to do on red/yellow molded stuff in the future so its all a matter of trial and error.

Edited June 27, 2016 by RickRollerLT1

[High octane]

On colored plastic bodies, after I scuff up the plastic a bit I use silver, then primer, then my color & clear coats and have never had a problem with bleed through.

[Ace-Garageguy]

For what it's worth, red pigment "bleed" was a real problem when color-changing over red enamel in the early days of this writer's car-painting adventures, and one of the reasons "sealers" were developed in the first place. Different pigments react differently to various solvents, too.

[Agent G]

I have had yellow bleed through back in the day as well as red. The owner of the LHS I frequented recommended silver paint. His theory was the metallics used for the pigment were able to block bleed through. It worked well and showed no bleed through with an enamel clear coat. I haven't attempted that with a clear lacquer.

G

[peteski]

Assuming that EVERY red styrene formulation is identical and that they will all bleed or not bleed equally is probably a bad idea, as are most assumptions.

Until every red styrene has been tested with identical prep and coating materials under controlled and repeatable conditions, there is simply NO BASIS to make a blanket statement either way.

 

That is exactly what I was going to say. Over the years there were many different formulations of polystyrene and dyes used to tint it.  Plus, different companies use different sources for their raw materials.  Next are dozens of different paint brands which modelers use (and those paints can have different chemical composition).  So what Snake proved was that the red dye in the plastic piece he painted and the paint he used did not react. But that is a very small sample of what is out there.

[unclescott58]

I need to throw a little twist into this. I have the Ertl reissue of MPC's 1/16 scale '63 Corvette molded in black plastic. I want to paint it red. Because of past problems with colored plastic I am a little worried about this. I plan using Tamyia's white primer. Then a Tamyia Red. Any thoughts on this? Will I be okay? Or will I have problems?

[Snake45]

I need to throw a little twist into this. I have the Ertl reissue of MPC's 1/16 scale '63 Corvette molded in black plastic. I want to paint it red. Because of past problems with colored plastic I am a little worried about this. I plan using Tamyia's white primer. Then a Tamyia Red. Any thoughts on this? Will I be okay? Or will I have problems?

I don't think you'll have much trouble. I've never heard of anyone complaining about black plastic "bleeding through." I've never used Tamiya White primer but I've found in trying to paint black or dark blue or dark green plastic white, it's usually a good idea to lay down a coat of medium or light gray primer before going to the white primer. One coat of gray covers dark plastic better than three or four coats of white. So one gray primer, then one white primer, then you should be good on whatever red you want to lay on that.

Also, I'm convinced that part of the problem with red "bleedthrough," whatever its chemical or physical cause(s), is the long wavelength of red color/light is helping it come through lighter paints. (This is why you almost never hear anyone complaining about blue or green "bleedthrough," I believe.)

[paul alflen]

I need to throw a little twist into this. I have the Ertl reissue of MPC's 1/16 scale '63 Corvette molded in black plastic. I want to paint it red. Because of past problems with colored plastic I am a little worried about this. I plan using Tamyia's white primer. Then a Tamyia Red. Any thoughts on this? Will I be okay? Or will I have problems?

I WOULD PAINT A SAMPLE OF THE PARTS TREE FROM THAT KIT TO SEE IF IT WORKS !

[Draggon]

So why doesn't everyone just airbrush acrylic on red/yellow bodies? Water based acrylic, not acrylic lacquer. That would solve the problem, yes? They do make clear too. Testor's Aztec clear is fantastic. 

[unclescott58]

So why doesn't everyone just airbrush acrylic on red/yellow bodies? Water based acrylic, not acrylic lacquer. That would solve the problem, yes? They do make clear too. Testor's Aztec clear is fantastic. 

Not everybody uses, or even has an airbrush. 99% of the time I get great results using lacquer paint straight from a can. Especially Tamiya. Though I've had pretty good luck with Testor's One Coat lacquer too.

[unclescott58]

I don't think you'll have much trouble. I've never heard of anyone complaining about black plastic "bleeding through." I've never used Tamiya White primer but I've found in trying to paint black or dark blue or dark green plastic white, it's usually a good idea to lay down a coat of medium or light gray primer before going to the white primer. One coat of gray covers dark plastic better than three or four coats of white. So one gray primer, then one white primer, then you should be good on whatever red you want to lay on that.

Also, I'm convinced that part of the problem with red "bleedthrough," whatever its chemical or physical cause(s), is the long wavelength of red color/light is helping it come through lighter paints. (This is why you almost never hear anyone complaining about blue or green "bleedthrough," I believe.)

I like your suggestion of laying down some gray primer first. That makes a lot of sense. I've used both Tamyia's white and grey primer with very good results. Recently somebody in another thread showed a Tamiya red or pink primer. I thought this was a little odd. When asking the propose of this colored primer, I was told it was best for use under red paint. So I'm wondering if I should lay down one coat of Tamiya grey primer over the black plastic? Then the Tamiya red (pink?) over that? And finally a Tamiya red? Or rather than hunting down the Tamiya red primer, which I've never seen available around here, I just stick with Tamiya white primer for my second coat?

[unclescott58]

I WOULD PAINT A SAMPLE OF THE PARTS TREE FROM THAT KIT TO SEE IF IT WORKS !

Of course. But, I also trust the advice of the guys here. There are some pretty knowledgable people posting on these threads. Who seem to be more than willing to share their wisdom. And you get to know who's advice you can trust here. And who's you can not. For example, despite the fact that I may not agree with Snake's views on everything here. Over all I've found that he seems to have a pretty good grasp on what works well. And what doesn't. His advice of laying down grey primer over black plastic makes sense to me. Whether I agree with his conclusions on whether red plastic bleeds through paint or not. I don't know? But, it sure seems like it to me and other I know.

As far as Snake being right or wrong on the issue red (or any other color) bleeding through. I really don't care in the long run. The more important question is how to prevent it? I've heard many different theories and suggestions on solving this problem. I just want to know what works? I hate any plastic molded in any color other than white. 9 time out of 10, one shot of a good primer has solved the problem for me. But red and yellow at times does seem to be the exception.

[Snake45]

I like your suggestion of laying down some gray primer first. That makes a lot of sense. I've used both Tamyia's white and grey primer with very good results. Recently somebody in another thread showed a Tamiya red or pink primer. I thought this was a little odd. When asking the propose of this colored primer, I was told it was best for use under red paint. So I'm wondering if I should lay down one coat of Tamiya grey primer over the black plastic? Then the Tamiya red (pink?) over that? And finally a Tamiya red? Or rather than hunting down the Tamiya red primer, which I've never seen available around here, I just stick with Tamiya white primer for my second coat?

I have laid gloss red over both a red primer (Testor Rust, to be specific) and over white and while both will work, red over white looks a bit brighter, if that's what you're going for.

Red paints (and yellows, too) seem to be more translucent than some other colors for some reason.

[Art Anderson]

There is no pigment that "leaches" out of plastic, only paint that isn't opaque enough.

Thus endeth the lesson.

Except, there are pigments, and then there are dyes.  Back many moons ago,  plastic feed stock manufacturers had a much larger "bag" of pigments that could be used to color polystyrene--over the years, a good many of those have been prohibited for ordinary consumer products due to their toxicity.   I do not recall EVER having a problem with "color bleed through"  until perhaps the late 1970's.

Art

[TarheelRick]

Don't know if it means much or adds anything to the conversation, but I have noticed when I do any sanding on red plastic it bleeds through no matter what I use.  I have tried them all, except for the Future suggestion.  Primer/sealers, silvers, clear prior to primer, different brands primer, etc., etc. I still get red bleed through.  Personally I think it is some satanic force messing with my paint (tinfoil hat anyone?).

[unclescott58]

I have laid gloss red over both a red primer (Testor Rust, to be specific) and over white and while both will work, red over white looks a bit brighter, if that's what you're going for.

Red paints (and yellows, too) seem to be more translucent than some other colors for some reason.

Again I'm going with your suggestion on that one too. A fairly bright red is what I want. So a white prime it will be.

[unclescott58]

After the gray of coarse.

[Snake45]

Except, there are pigments, and then there are dyes.  Back many moons ago,  plastic feed stock manufacturers had a much larger "bag" of pigments that could be used to color polystyrene--over the years, a good many of those have been prohibited for ordinary consumer products due to their toxicity.   I do not recall EVER having a problem with "color bleed through"  until perhaps the late 1970's.

Art

Art, have you ever run across a chemical or solvent that will draw the color--pigment, dye, whatever--out of styrene without actually dissolving the styrene itself (a la MEK)?

[AC Norton]

.......this thread is kinda like a DOS EQUIS beer commercial, where Snake is the most interesting man in the world.....well, sorta,,,,so, instead of everyone wasting more and more time on this particular thread, lets make it easy....use Tamiya white, or their pink primer, making sure the car is prepped properly in the first place....regardless of color of plastic,,,,,then, blow a couple of light coats of your color over the car, let that tack for 10 to 20 minutes, then apply the final number of coats you prefer. all this bleed thru stuff will become a myth, and Snake can go back to measuring dune buggy steering wheel- to- crotch interior sizes, and other stuff the most interesting man in the world may  endeavor to do .........maybe.....the Ace..... 

[Snake45]

HAHAHAHAHAHAHAHAHA!

Well played, Ace!

[AC Norton]

HAHAHAHAHAHAHAHAHA!

Well played, Ace!

.......I thought that may get a response from you, Richard....and remember the famous words,,,,,STAY BUILDING, MY FRIENDS.....lol...

[SteveG]

Both my Dad and my Brother worked in the Plastics Industry, my brother worked in their lab for years and they tested for all kinds of performance issues.  Color Bleed is a well known Performance issue in the industry.  I also heard it called Color Migration.  Organic solvents like lacquer can definitely pull some colorants out of some plastics.  

I been avoiding the kits that are molded in bright colors just because the Lacquer thinners I use are definitely on the hot side.  I recently bought some Vallejo Acrylic-Polyurethane white surface primer that looks promising but I haven't had a chance to use it yet.   If get good results I'll definitely post it.

-Steve

 

[Snake45]

Both my Dad and my Brother worked in the Plastics Industry, my brother worked in their lab for years and they tested for all kinds of performance issues.  Color Bleed is a well known Performance issue in the industry.  I also heard it called Color Migration.  Organic solvents like lacquer can definitely pull some colorants out of some plastics. 

I been avoiding the kits that are molded in bright colors just because the Lacquer thinners I use are definitely on the hot side.  I recently bought some Vallejo Acrylic-Polyurethane white surface primer that looks promising but I haven't had a chance to use it yet.   If get good results I'll definitely post it.

-Steve

 

Interesting. I'm gonna see what I can google-fu about color migration in the plastics industry. Thanks for the tip!