Working Around Red Plastic?

[JollySipper]

I'm working on a Thunderbird SC that's molded in red. Of course, I want to paint it white..... I've tried to seal it with aluminum paint, but when I spray the DupliColor on it, the dyes still bleed thru. I read on here about someone using ( I think it was) oven cleaner to pull the pigments from the plastic.... Does that sound right? This is the only molded-in-color kit I've had that I can't cover the dyes from...

Thanks for any help!

[crazyjim]

I've heard of using a coat of Future.  Mr. Obsessive says using a white primer but I can't remember the brand. Sorry.

[peteski]

Wasn't it Kilz primer?

Edited September 15, 2021 by peteski

[jchrisf]

I just read an article by Bob Downie @Zoom Zoom about this very subject in an old issue of Scale Auto.  He uses Zinsser BIN Shellac Based Primer Sealer to prevent the bled through.

[crazyjim]

That's it, Peter. Kilz. Thanks.

I've heard of the BIN stuff too.

Edited September 15, 2021 by crazyjim

[Snake45]

1 hour ago, JollySipper said:

I read on here about someone using ( I think it was) oven cleaner to pull the pigments from the plastic.... Does that sound right? This is the only molded-in-color kit I've had that I can't cover the dyes from...

You probably read my posts about oven cleaner NOT pulling dyes out of plastic, and challenging anyone to come up with a chemical that WOULD take any color out of plastic without also dissolving or crazing the plastic. I've had this challenge out there for years and no one has met it yet. 

There's no such thing as color "leaching out" of plastic, just primers and paints that aren't opaque enough. 

[JollySipper]

1 hour ago, jchrisf said:

I just read an article by Bob Downie @Zoom Zoom about this very subject in an old issue of Scale Auto.  He uses Zinsser BIN Shellac Based Primer Sealer to prevent the bled through.

Cool.... I just saw on Amazon that you can get it in an aerosol can. This will most likely be what I do.......

Thanks!

[Jim B]

This is good info.  I have a Revell Split Window Corvette that is molded in the Dreaded Red.  Might have to try this.

[JollySipper]

46 minutes ago, Snake45 said:

There's no such thing as color "leaching out" of plastic

If you say so, Richard....

I did just see it happen this morning, tho... I sprayed a spare part with the aluminum, then primed it. I then put the white DupliColor on (which is a hot paint) and watched it turn pink......... I'll surely seal it before trying to paint any important parts.....

[Plowboy]

1 hour ago, Snake45 said:

There's no such thing as color "leaching out" of plastic, just primers and paints that aren't opaque enough. 

I used to have the same belief......until it happened to me. It happened on this model.

It's the Lindberg kit molded in glossy yellow. Didn't happen when I primered. Didn't happen when I painted it. Didn't happen when I did the first coat of clear. It happened when I shot the second coat of clear! The yellow came through turning the blue a greenish color. Luckily, I had only done the bed and grille. I let them dry, sanded lightly, shot a coat of color and a coat of clear. Primer and all paint are Tamiya. So, the dyes do leach out. Even with paint formulated for styrene. 

[peteski]

1 hour ago, Snake45 said:

There's no such thing as color "leaching out" of plastic, just primers and paints that aren't opaque enough. 

I know you are a non-believer, but one would think that silver paint would be opaque enough.  Metallic particles should be 100% opaque.  They are to light (if you paint a piece of transparent plastic with silver).  I would also say that black primer would be opaque enough (for the same reason).  So if you were to paint a red plastic model with black primer, then white primer (which was opaque enough not to show any black), then the white primer, or the white top coat over that white primer turned pink, what would you say?

[Snake45]

Again I challenge: Tell me the chemical that you can put on a rag and rub on red plastic, and the rag will be turned red to any degree at all but the plastic will not be damaged, crazed, frosted, or fogged in any way. I'm still waiting to learn what it is. 

[peteski]

1 hour ago, Snake45 said:

Again I challenge: Tell me the chemical that you can put on a rag and rub on red plastic, and the rag will be turned red to any degree at all but the plastic will not be damaged, crazed, frosted, or fogged in any way. I'm still waiting to learn what it is. 

I cannot. However I don't believe it is that simple.  The leaching process is much slower and likely more complex than just running the solvent-soaked rag over the plastic surface.

I would compare it to what happens when certain types of vinyl tires softening bare plastic, leaving marks on the surface.  You can't simulate that with a "rag test".

Edited September 15, 2021 by peteski

[Draggon]

Has anyone thought of dyeing the plastic another color? There are ways to do this all over the web. I guess it would depend upon how deep the dye was absorbed into the plastic, but it might work as a barrier. 

[SteveG]

1 hour ago, peteski said:

I cannot. However I don't believe it is that simple.  The leaching process is much slower and likely more complex than just running the solvent-soaked rag over the plastic surface.

I would compare it to what happens when certain types of vinyl tires softening bare plastic, leaving marks on the surface.  You can't simulate that with a "rag test".

Peter is right, your rag test isn't exactly how plastic colorants are tested for things like bleed fastness, the solvent fastness of pigments or the solvent solubility of dyes.  There are actual standard lab tests for those real issues in the plastics industry.  Natural high impact polystyrene or HIPS is actually a very translucent white so all model parts other then the water clear items have some colorant added to them. 

 Anyone who has tried to paint over brightly colored polystyrene with solvent based products and didn't have a problem, consider yourself lucky.  After I switched to collision repair grade paints, I stopped attempting to paint over anything molded in brightly molded colors, especially red or yellow.  It only took a couple of failures to learn my lesson.  I can tell you the reactions I saw had nothing to do with the opaqueness of the finishes I was using. 

For the record if it's not clear already, I'm no fan of molding kits in any heavily colored plastic.  But if the boss says there's still going to be some kits molded in color that's what going to happen.  Not everybody can or wants to paint to their model builds.  

-Steve  

 

[Chariots of Fire]

I've had mixed results.  A while back I built this aerial ladder model using two Monogram snap kits.  The kit plastic in each case was yellow the first try.  I primed the cab with gray primer.  One one of the cabs the yellow came through.  On the other it did not.  So I scrapped the yellow one and went to the red ones.  But before cutting them apart and gluing I primed the inside of each cab to see what would happen.  One nothing.  On the other the red came through.  I got another red cab and again painted the inside with primer.  Nothing happened.  So I proceeded to splice the two non-reacting cabs together as shown.    Conclusion:  Some plastic is reactive and some is not so it must be the type of plastic used in the molding process that causes the trouble and that all plastic used in the same type kits is not always the same.  (Ignore the date on the photo.  It was not set in the camera.)  And below is the end result.

[JollySipper]

31 minutes ago, Chariots of Fire said:

Some plastic is reactive and some is not

This is what I'm finding out...... I've painted an AMT kit molded in orange, and a Monogram kit molded in red, but this old Revell kit is kicking my butt trying to work with it. I'll get a stain blocking primer, hopefully sometime this week..... I'll let you guys know how it goes.....

[Modelbuilder Mark]

I have a few of these colors, and find them helpful,  Badger Stynylrez.

https://www.amazon.com/Badger-Air-Brush-Co-SNR-210-Stynylrez/dp/B00K3KGWQS/ref=asc_df_B00K3KGWQS/?tag=hyprod-20&linkCode=df0&hvadid=167148482147&hvpos=&hvnetw=g&hvrand=10377529976530959500&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9053836&hvtargid=pla-305941821090&psc=1

If you are willing to use other products, I know some folks Kilz barrier, and they thin it with Alcohol. I have yet to try this, but given it is used as a moisture and even mold barrier, I can see how it would work. 

 

 

 

 

[GLMFAA1]

Use of Easy Off: It will strip paint from models, it will strip chrome parts. It will remove the tint from old Johan tinted plastic parts, ie the red and blue trees from the Plymouth police car and tailights. It will not effect injected colored plastic, Injection plastic starts out as beads which are heated and injected into a mold. The coloring is in the beads injected so the amount of coloring effects the chemical composition after heating. The color does effect the process as different colors need different temperatures to melt. If you have an old military or silver airplane kit you might find veins of color changes in the plastic. 

greg

[slusher]

On 9/15/2021 at 1:02 PM, Plowboy said:

I used to have the same belief......until it happened to me. It happened on this model.

It's the Lindberg kit molded in glossy yellow. Didn't happen when I primered. Didn't happen when I painted it. Didn't happen when I did the first coat of clear. It happened when I shot the second coat of clear! The yellow came through turning the blue a greenish color. Luckily, I had only done the bed and grille. I let them dry, sanded lightly, shot a coat of color and a coat of clear. Primer and all paint are Tamiya. So, the dyes do leach out. Even with paint formulated for styrene. 

I agree I believe die bleeds trough comes out of the plastic and really I was on the fence but a year ago with a model moles in red. I ended up giving up. Lost heart fooling with it but I have not yet had any problems with yellow or orange. I did talk with a friend about this once and if molded color cars are ever in a hot temperature I causes any red or orange harder to deal with. He kept his models in the attic . That was his belief..

[bisc63]

I've primed an older Monogram '66 Chevelle kit body, molded in red and a notorious bleeder, with a cheap filler primer (light gray) from Harbor Freight called Iron Armor. This was mentioned in another thread here somewhere. It's been several weeks, and absolutely no color has bled through. Pretty nice primer to work with, and relatively inexpensive.

[Chariots of Fire]

I don't think heat is the culprit.  All kits that I have had that have this problem have been in my basement where temps are cool even in the heat of summer.  Definitely an issue with the plastic itself.

[robdebie]

I remember reading in a book on industrial paint that the red dyes for plastic are notorious for being able to dissolve in paint solvents, and thus moving into the paint itself. To me it sounds like different paint solvents could be the answer. Like using a waterbased acrylic paint instead of (say) an enamel with added white spirit. But that's just a hypothetical example.

Rob

[Tom Geiger]

my dilemma was a Dodge Caravan molded in red.  Primed and painted with Duplicolor it looked great. I then painted all the trim and added my decals.

A friend was crowing about Testors One Shot Clear so I wanted to try it. Disaster! It reacted with the red plastic under all that Duplicolor turning the bright blue darker.  Note that the side window area was clear plastic so it didn’t change, nor did any area under decals. Just where the One Shot had direct contact with the red plastic.

You can see in this photo that the Testors One Shot Clear melted the black Sharpie I used for detailing (another suggestion from a board!)  So I don't use Sharpies anymore!   Oh the lessons hard learned!

I stripped the whole thing and started over. Someone mentioned sealing in the red plastic with silver, so this time I did the Duplicolor gray primer, then a silver coat. I planned on the blue over it, but the silver looked good so I kept it as the body color. This time I used Tamiya clear!

 

Edited October 5, 2021 by Tom Geiger

[CabDriver]

Something maybe-helpful; I have never had ANY trouble with colored plastic showing through when using Createx airbrush colors.  White over red, black, blue or anything else - never had an issue.

Maybe acrylics are less susceptible to this phenomenon?