Paint problem. Advice?

[nscaleSPF2]

Craig, you don't mention the temperature/humidity that existed during your paint job(s).  It's possible that these can affect your results.  What do you think?

[craigolio1]

I did it indoors in a temperature controled environment. I would say 21(72) and I don't know what humidity. I can check tomorrow.

Craig

[craigolio1]

So I did the packing tape test.

Kato SD: no problem.
Kaslo shops caboose (the one with paint still on it) no problem where oddly the other Kaslo Shops caboose it practically fell off.

Briggs Models M420: large portions came off. Not repairable.

Briggs Models 8-40CM (two of them). Little bits came off. Likely repairable but why bother.

So tomorrow  I'm stripping all but the caboose and the SD40-2.

Craig

[Angus Shops]

Sad news. However, not really a surprise; resin is well known for poor paint adhesion, while plastic is easier to deal with. I'm convinced that most of this sort of stuff is mostly alchemy and, if you'd cursed Gordon Campbell for selling BC Rail to CN before you started painting, you'd have no problem.

Geoff

[peteski]

Sad news. However, not really a surprise; resin is well known for poor paint adhesion, while plastic is easier to deal with. I'm convinced that most of this sort of stuff is mostly alchemy and, if you'd cursed Gordon Campbell for selling BC Rail to CN before you started painting, you'd have no problem.

Geoff

Not alchemy at all.     The way I see it Tru-Color paint uses acetone as solvent. Acetone dissolves the plastic shells are made of (ABS or polystyrene). So when the paint is properly applied to the shell it actually partially melts into the surface of the plastic.  But acetone has no effect on urethane resins. So the paint simply sits on the surface. If there is even a smallest amount of contamination on the surface of the resin that even worsens the adhesion.

[daniel_leavitt2000]

Craig! Be very, very careful stripping resin. Do not use anything other than 91% isopropyl and do not let the shells sit in there for more than a minute or two. And even with that, its still a 50/50% chance of ruining the shell.

Trust me on this one.

[Viperjim1]

Have you tried using frisket paper , or micro mask as these do not have a strong adhesion and you can cut the design out and paint your shells and it doesn't leave a paint line like masking tape does   I've used this for  camoflouging aircraft , you just have to make sure you use a new number 11 exacto blade and you don't have to press hard as you'll leave scribe marks on your project.

[peteski]

Craig! Be very, very careful stripping resin. Do not use anything other than 91% isopropyl and do not let the shells sit in there for more than a minute or two. And even with that, its still a 50/50% chance of ruining the shell.

Trust me on this one.

I'm curious which specific companie's resin was so delicate.  All the urethane resin castings I have ever dealt with (either bought or made myself) are not affected by stronger solvents (such as lacquer thinner or naphtha).  I don't leave the part sitting in the solvent for hours but it is not affected in the time it takes to clean it.

[Doc Frankenfield]

I agree with peteski  improper cleaning is probably the culprit.
dawn, acetone and then scrub with comet of the like or make a paste of baking soda and scrub. the issue is that almost all resin is cast in silicone molds, if brand new ,the molds will leave a little silicone on the cast part. if old, molds are usually sprayed with a release  agent, silicone, which can actually become the surface of the cast part.
in either case all traces of silicone must be removed from the surface before you can paint.
plastic and silicone will not  act the same. the only commonality is that they both will have a release agent of some sort present, and it must be removed prior to painting.

really old urethane resins, 9 30 plus years ol) had issues with improper cure and porosity. brittleness.
if your resin is weeping, it wasn't mixed properly!

[craigolio1]

I really feel like I did a good job of cleaning.  I didn't use thinners or baking soda but they soaked in resin prep, soaked in dish soap, and then were scrubbed with a soft tooth brush and were never touched with un-gloved hands.  I stored them in sealed ziplock bags.  Obviously it's possible that I didn't do such a great job but I've painted a dozen or so other resin models (with laquers) and had no issues.  I find it unlikely that I've switched to this paint and now have problems with my cleaning. 

I don't use chemicals to strip.  I use Van Halen, and a Badger sand blaster. If there ARE any release agents or silicone on the model that will take care of it.  Then I'll prime and paint and see what happens.  I didn't get the chance to strip them today but I'll report back with some reults when I have them. 

The only thing weeping is me.

Thanks again for all of the help guys.

Craig

[bnsfdash8]

I'm curious which specific companie's resin was so delicate.  All the urethane resin castings I have ever dealt with (either bought or made myself) are not affected by stronger solvents (such as lacquer thinner or naphtha).  I don't leave the part sitting in the solvent for hours but it is not affected in the time it takes to clean it.

I had a Briggs models resin speeder and didn't like the paint job so I dunked it in some 91% alcohol like I normally do to strip models and came back in about 15 minutes to it being soft and basically falling apart.

[Nick Lorusso]

Craig,
Did you primer first?

[craigolio1]

I have tried micro mask before but wasn't able to cut through it/around details without leaving marks on the model.

I stripped them today. Strangely the Badger sandblaster didn't really work. It's almost like the paint was very hard, just not attached to the models very well. So I dipped them in Acetone and the paint almost fell off. I didn't have to submerge them more than a few seconds.  I don't think it hurt the shells. I did notice that one of the side window frames in a 8-40Cm isn't perfectly straight but I think this was a casting anomaly as for this to have happened because of the Acetone would mean something else would have to shift, like the can roof or the side, which is impossible as its one piece and nothing else is crooked.

No I did not prime, but I am now!


Craig

[peteski]

I didn't know that Van Halen can be useful fro stripping paint?  Do you blast it really loud when stripping paint? 

I still have a feeling that even if you primed the shells where the paint did not adhere well, the paint along with the primer would still have lifted with the masking tape.  Unless the problem all along was the paint applied too dry (like I explained earlier).  The drier-applied paint would have adhered better to the primer than to bare resin.

Now that you used acetone (which as you experienced will very quickly dissolve the Tru-Color paints), you have most likely cleaned whatever contaminant was on the resin surface (and/or simply stripped the dry-applied paint). At this point I would not expect to see any more adhesion issues (with or without primer).

Bnsfdash8:

I  have never owned any Briggs resin castings so I don't know what kind of resin the use, but all of the urethanre resins I have used (like Alumilite, SmoothOn and urethane items made by Fine N Scale, DKS, Chooch, and few others I don't recall now) were imprevious to Acetone (which is much stronger solvent than 91% isopropanol).

[craigolio1]

I'm planning to "prime" it with that plastic adhesion promoter in hopes it will help.