Paint problem. Advice?

[craigolio1]

Hey everyone.

Over the past couple of weeks I've been painting these models:



The paints are True Colour. With the exception of the SD40-2, all of the models pictured here are resin kits. One not pictured, another caboose like the one in the picture , was painted just the blue colour on the bottom half. When I went to apply masking on top of the blue, to prepare to shoot the red, the tape pulled all of the blue paint off.

Now, all of the models you see pictured were painted white first with exception of the effected caboose. It was not painted white first. Masking was applied over the white. Then the top was masked to shoot the blue and the bottom was masked to shoot the red. Except for one small spot on one resin loco, that is easily fixed, all were masked and unmasked without issue.

These locos were thoroughly washed first with Sylvan Resin Prep and from then on have not been touched by ungloved hands. No primer was used as I read some where that it wasn't needed with these paints.

I tested a bit if the blue on one part that won't be visible and it scrapes away with a knife without too much effort, but not like on that caboose. Tape for example does not remove the blue on this test part.

So here is the question. Do I sandblast all of these locos and start over with a good primer, (I have a limited supply of Floquil I keep for special occasions)?  Or do I just do this on the one caboose? 

Obviously I have a ton of work in these paint jobs thus far. I really don't feel like talking them back to te beginning, how ever it will hurt more if they start shedding years down the road after decaling and weathering etc.

I really don't know what to do. I'm leaning towards just redoing the one affected caboose.

Thanks for your input.

Craig

[ns737]

HI it is hard to say . I had painted some ns engine shells with true paint. and about two months later I had some paint flak. I did not prime the shells. so I striped them and primed them then repainted the black, masked and painted the white with no paint lift. to my conclusion I prime all now.

[daniel_leavitt2000]

Acrylics and resins do not mix well. Many pressure treated resins will weep oils long after casting. I usually let my castings dry about 10 days to make sure they are dry. Even after washing with dish soap the urethane resins can be tricky to paint. I ALWAYS use a light primer before painting resin shells. I learned my lesson well after painting one of Grant's F45 shells with Floquil, the shell melted.

I swear by bumper primer used for automotive repairs. It plays nice with resins and paints and adheres well to both.

[craigolio1]

That's very interesting. I didn't know that resins sweat. Strangely the caboose casting is probably 15 years old. The other ones are much newer.

By bumper primer do you mean the plastic adhesion promoter or used on plastic carpenters to promote paint adhesion? If so that makes me very happy because I hapen to have a can in the basement.

It sounds like to be safe I should strip them and start over.

[BobRunty]

I've had a couple instances where Tamiya masking tape has pulled Tru Colour off too. All on unprimed models. Never had it happen with Polyscale or the older hot Floquil. I've only used Tru Colour now for a couple of years so it's still kinda early to tell if there will be a problem but other than the tape pulling it off i haven't had issue with flaking.

The automotive bumper or adhesion promoter is a good idea on resin. I use it on acetal handrails but never thought to on resin models.

N
Bob

[craigolio1]

Exactly what I thought, and on handrails it works very well. Im going to give that a try on the caboose and if the result is what I'm expecting then I'll strip the others and start over.

Thanks.

Craig

[Scottl]

This is really unfortunate, they look so well done.  Hopefully it won't be a complete re-do for the fleet. 

However, if you are going to get out the paint again, maybe you could paint another loco in that scheme...  I can donate paint to the cause.

[peteski]

Is the name of the paint you're using Tru-Color or True Colour?

[jnevis]

I completely agree with using a primer. I've been shooting a lot of resin and metal minis lately and the ones I do without priming first the paint doesn't even stay on long enough to hit with clear coat.  I've been using Rustolium auto primer with pretty good results. I have a can of their plastics primer but it was less than ideal

[Angus Shops]

I use Model Master sprays in rattle cans as primer on urethane. It sticks really well; never had a problem with paint lifting when removing masking tape, and it's easy to apply a nice light coat. As for the locos with the paint that seems to be well adhered, I'd give them a 'stress test'; do a test with some really sticky tape (packing tape comes to mind) and if the paint sticks, move on. I use Scalecoat paints (at least, I used to...) over the primer with no problem, but Scalecoat will not stick to bare urethane.

I've seen sweaty urethane but in my experience it is a result of old resins that are way past their best before date. Time doesn't seem to lessen the problem, it can't be cleaned because it keeps reoccurring, and the Model Master paint won't dry properly. In my experience it was a very obvious problem and I expect you would have noticed it early in your prep work if it was a factor in your caboose problem.

Geoff

[loyalton]

I also never had the problem with Polly Scale but perhaps nothing I ever painted was pressure-treated either. Good to hear that Model Master works fine for resin though I might have guessed from the Delrin-type trucks and couplers I've painted. HO resin builders always seemed to use primer, though.

With this material at least, Tru-Color is then acting no different from typical acrylic craft paint -- poor adhesion except to paper and card.

[craigolio1]

The paints are Tru-Color.

I'll try my DuPont Plastikote as a primer on the caboose and see how that works.

Nice to know the Model Master paints are an option. Can anyone tell me if they are still available in Canada?

Scott, email me.

Craig

[peteski]

The paints are Tru-Color.

So, that is organic solvent based paint and the solvent has acetone.   These paints should stick really well to plastics like styrene.

When I paint models I try to minimize the thickness of paint (so the fine surface details don't get covered up).  If the plastic color is neutral or similar to the final color I shoot Tru-Paint directly over plastic.  It has excellent adhesion.  Of  course I clean the shells really well by washing them in warm water and dish-washing detergent (but I use the detergents which do not contain any skin moisturizer). Sometimes I also rinse the shell using a 99% isopropyl alcohol.  I don't use any fancy plastic preps (which are most likely just some sort of alcohol solution and are way overpriced for the quantity I would use to rinse, not wipe the model with).

With (urethane) resin things get more tricky.  Again, I don't use any fancy cleaning solutions.  Urethane is usually highly resistant to solvents. After a good wash in warm water and dish-washing detergent (as I do with styrene shells) I usually dunk resin shells in lacquer thinner to get them *REALLY* clean.  In most cases that is enough of a prep to shoot them directly with Tru-Color paint.  If needed, I use Tamiya fine primers (gray or white, as needed) as an undercoat for the final color.

Another important thing is to make sure the paint goes on wet. Many modelers seem to spray their models in such a way that the paint goes on partially dry.  That will cause poor adhesion as the atomized paint dries partially before hitting the model surface. That also causes rough paint finish.  Spray it on wet and the paint should adhere really well.

[nickelplate759]

I don't know about these particular shells, but I have used True Color paints on a Skytop Models resin shell (the REA express reefer / troop-sleeper conversion) and the results were excellent.   In that case I followed the directions to clean the shell first in mineral spirits, then in detergent and water.  I did not use a primer.       Adhesion has been far superior to some Fine-N-Scale and Wheels Of Time resin shells where I only cleaned in detergent and water.

George

[craigolio1]

Hmm that's interetesting. I cleaned with resin prep, then washed in detergent, rinsed and air dried and the paint went on wet for sure,  but I didn't dip in any kind of thinners or solvents.

After I do the sticky tape test, good idea by the way, and strip if needed I'll be sure to include the dip before I shoot.

I'm with you Pete, I want as few layers as possible as well but the plastic adhesion promoter doesn't add hardly anything, it goes on so thin so in going to try that as well.

I hate repainting. I'm only doing it once.

Thanks again.

Craig