Paint Adherence problems

[cool8or]

Hi guys. In the last years, I have been painting with automotive laquer paints, bought in a automotive paint store, and used also the regular thinner (called "acrylic" but obviously is not water based) bought in the hardware store.

As you know, I been having some adherence problems in some resin kits, and I though that the problem was the resin itself. But yesterday I was finishing a Hasegawa plastic model , and when I retire some masking tape (Tamiya), some paint take off. It was very frustating, due the valk was almost finish.

I use Mr Surfacer as primer, but when this happens it's also removed by masking tape, so when this happens no paint is left, just the plastic. Fortunately, this happened to me so much that right now I'm an expert solutioning these issues, and you can't see it in the final result.

I have several Hase kits painted with this same paints and nothing happened in the past, so I don't know what happened this time... May be is the brand of the thinner (not always I find the same brand). If I can't identify the cause, I' m thinking in discontinue the use of this paints an only use Mr. Color paints. Fortunately, I found a web site that have the complete catalogue of this paints: www.sealmodel.com

But, in case that I discontinue the use of my automotive paints, I wondering about the diference between the regular thinner, bought in the hardware store, and the Mr. Color thinner... Do you think that deserves to pay more, and wait 3 months (delivery time for surface shipping) to have this thinner? May be it's almost the same product, I don't know, that' why I'm asking.

In the worst scenario, I can use Mr. Color thinner only to thin the pain, and use regular thinner just to clean the airbrush and tools.

Any comment will be welcome.

[mslz22]

If the lifted paint is going all the way down to the plastic, both resin and styrene, taking even the primer with it, I would look at 2 factors to start with.

1 Are you cleaning the parts, and it may not be what you think. I have had problems with paint/primer adhering BECAUSE I cleaned the parts. The issue is that even mild soap can leave an invisible barrier between the plastic and the primer. I mostly only build kits that i have cast and straight styrene kits like Hasegawa, and do not clean the parts at all and have little to no problems with paint lift. The caveat with that is of course on kits i cast I do not use any mold release at all. I have a few Club M kits i want to build, and they are very slippery, for those i am going to use a walnut shell etching process.

2.is the Mr. Surfacer your are using spray can or jar/mix in airbrush. I am not as familiar with Mr Surfacer and not sure if they even have a jar/airbrush primer. If it is a jar mix you may be on the right track to look at the thinner/solvent. If it's the spray can I would ask about how thin you are laying the first couple of layers of primer.

mike

[HWR MKII]

If i have areas i suspect of being troublesome. i test them out. If the problem occurrs i wipe the area with alcohol. If the problem still persists and isnt a film but is from the surface being too smooth i scrub it with a medium grit sandpaper to give it more bite. After a prime and rub the area should be invisible under paint. I have the issue more in the higher end resin kits where teh surface is too smooth for any paint to bite.

[derex3592]

Good thread here! I have had this problem with on plastic and resin kits myself. Nothing worse! I did a little experiment the other day and took some scrap parts out of an old plastic F-16 kit, never washed, nothing at all. Sprayed Tamiya acrylic paint on it and let it sit overnight. Layed down perfectly. The next day I stuck a piece of Tamiya masking tape on it, pressed it down pretty good and let it sit for another day. Went back and not even very gently pulled up the tape...guess what??? NO PAINT LIFT! This leads to believe that something is going on when I wash and or primer my kits....

[Valkyrie addict]

Same as HWR, when this sort of stuff happens to me I remove all the paint, clean in warm soapy water and scrub, do some light sanding with 400 grit and then alcohol wipe, wait for a day that is not too humid and after priming I leave setting until the next day.

But I think you might have a problem with your primer.

Edited November 16, 2013 by Valkyrie addict

[cool8or]

This is a very tricky problem. At the beginning of buildind, I test the adherence of Mr Surfacer and everything is perfect, and I trust that all is OK. Even if I try to reproduce the problem, I never get it. But, after several weeks, or months, after you paint the base color, postshading, and masking to apply the secondary colors, is when the disaster occurs: not in several pieces, only in just one or two. . This time, was more frustrating, because I had the kit ready, with decals, flat coating, and the only work left was a metal finish section. I left this work to the end because the metal colors looks better with their original shine, and, talking about this specific case, masking before the flat coat would be more dificult.

Mike, I never have cleaned plastic kits. Now I was considering to do it, so thank you for your advise.

HWR, I do exactly what you do. As I said before, fortunately I can fix the disaster and it looks like never happened.

Obviosly, this problem don't happen with water based or enamel paints, but sadly adherence is not a synonymous of resistance. As you already know, a couple times per year I go to modeling or collector exhibitions, so I really need that my kits to be resistant to friction. In this aspect, enamel and water based paints really sucks.

[HWR MKII]

It could also be that your auto paints are too "hot" and are reactivating the Mr Surfacer causing it to lift. Surfacer is a cold laquer meaning its solvents arent very strong. It could be the solvents in the overlayers are stronger and breaking teh bond between the surfacer and plastic.

[cool8or]

Mmhm... That could explain it... And could the paint AND the thinner cause the same effect... I'll make some experiments.

[captain america]

It could also be that your auto paints are too "hot" and are reactivating the Mr Surfacer causing it to lift. Surfacer is a cold laquer meaning its solvents arent very strong. It could be the solvents in the overlayers are stronger and breaking teh bond between the surfacer and plastic.

I would concur with this evaluation. In my experience using pretty much all types of paint over the years, automotive paint and its solvents (up until just recently) tends to be very hot. My suggestion would be to obtain a primer from the auto paint store that is compatible with your paint. Preferably an epoxy primer, which is thinner than a high-build primer which is used for scratch-filling.

Also, surface prep is critical: light sanding, then thorough washing with soapy water and let the parts air dry.

[Kylwell]

Or get a hold of some Mr. Resin Surfacer or Mr. Primer Surfacer 1000 which is hotter than their usual line of primers. Also smells to high heaven.

[ahiachris]

How do you trim the masking tape after you apply it or before you apply the tape? If you trim the tape after applying them then you might have used too much force on the tape and causing the paint underneath to break. If possible it might be easier to understand the problem you encountered with pictures.

[PetarB]

I have personally had problems with Mr Surfacer lifting on a couple of resin kits. I tested on the same kit with Tamiya Fine Grey Primer (now my favourite) and I did not experience the same issue. Mr Surfacer has a nice velvety finish, but after my bad experience with it, I've given it a miss.

[cool8or]

Thank you guys. Good ideas and advices have been mentioned in this thread. To start, I'll follow Cap's advice, I'll go to the Automotive Paint Store and I'll buy a Primer from them. I have a lot of money invested in these paints so I have to give it a chance.

Thank you again!