Future cracks (eats) plastic and putty ?!?

The same thing happened to me once. I used Tamiya acrylics as the base color & waited a couple of weeks. Then I applied Future over it. In a few days I had paint cracks all over the model. At that time I asked the same question here. The general consensus was that the paint needed to cure longer, & that it was shrinking at at different rate than the Future, causing the cracks. I never did find out what length of time was sufficient to wait before overcoating.

Well...

I am not sure that it is the paint combination and only the paint cracking...

I can say only this: a) In the parallel, I am making an other Plane model Sopwith Triplane (new kit, very good plastics) and with exactly the same procedure (100% same!). Not a single crack, only slight putty shrinkage. b) An additional observation is that the cracks seem to be going deeper as it is just the paint level/layer.

For me it seems to be some chemical reaction: Future with the old plastic type making some kind of "aggressive-everything-eating- solution" ... I will not keep this plane near my bed in the night! :-)

Drazen

What did you use as an undercoat? Was the plastic washed and dried before you applied any paint to it? What did you thin your paint with?

IMO it is much, MUCH more likely that IF there is any chemical reaction going on, it is between the Gunze paint (and/or thinner) and the plastic, not the Future and the plastic.

I mean, have you tried painting the plastic (just test on some left- over sprue), NOT applying any Future, and leaving it for 2-3 weeks to see if there is any reaction?

I think you are being premature in blaming the Future coat when you have several variables in the situation.

Bruce Melbourne, Australia

In non-technical terms, Future is a very mild type of coating and it should not affect any type of hard plastic or resin. I highly suspect that it might have interacted with the other paint layers applied to that model. I suppose that one way of testing this would be to strip the model and see if the plastic has any visible signs of cracking. I think that the coats of paint under Future would be stronger suspects for melting plastic than the Future.

Peteski

I'm pretty well positive that in my case it was the paint (or Future) that cracked. I never bothered to investigate too closely, but perhaps I should.

yeah, future's essentially in a water-based solvent; hard to imagine that would attack plastic.

But is it the same paint/......

Future acts as a barrier keeping solvent vapors from escaping the paint layer?..... For various reasons paint can take a longgggg time to fully cure. And if the paint has gone skunky, or it doesn't like the thinner, or if it was a full moon......

I had the same thing happen- I think the Future and underlying paint contract at different rates, and this is what caused the ruin of my P-61

What was unclear in the original post is whether Drazen just speculated that the plastic was cracked or whether he actually stripped the paint and confirmed that the plastic was in fact cracked. That would make a big difference in the final explanation. At think that at this point we all have given plausible explanations for both scenarios.

Peteski

Exactly!

Peteski

I'd be more willing to believe that the paint hadn't cured yet and the Future just couldn't 'stretch' with it.

Bill Banaszak, MFE Sr.

Hi! Your logic seems also logical to me :-) To your question if it is the same Paint -> YES, it is absolutely the same paint Gunze + Future Also on the third Plane (Fokker D VIII which has similar old plastics) have found small cracks ... never had such problem before... Full Moon...

Drazen

me again...

I will try to save the job by small corrections. It really looks very nice: a lot of pre-shading and some Alclad metalizer detailing, scratch build insertions for wing connectors with fuselage, etc. Also decals are on the wings :-( I will be sad to ruin it in order to find cracks in plastics (or not).

What I can do is to paint few smaller parts I still have and did not need for this type of plane (they have been delivered in the same box) and try to simulate the cracks. If I manage to get cracks, I will clean the paint and see if it is the plastics or just the paint which has cracked.

Let's see when I am so far - please, be patient. I will write then here again.

Drazen

It is definitely just the paint that has cracked. What happened is that either the acrylic paint wasn't completely dry before you applied the Future, or you slapped on such a thick coat of Future that the ammonia in it softened the acrylic; and then the Future dried faster than the acrylic paint underneath it, which causes it to crack.

Paint shrinks as it dries. Normally it bonds to the surface of the model or the previous coat of paint, so it just shrinks in thickness. If the previous coat isn't completely dry, or becomes softened by the new coat of paint, there's nothing to keep the new coat from shrinking sideways, and pulling the underlying soft paint with it; it pulls itself apart, creating cracks in the finish. The plastic isn't affected.

Low, dry heat. I hear some modelers use food dehydrators.

Yes, many modelers (including me) use food dehydrators. However I mostly use organic solvent based enamels (not water-based acrylics). I keep mine between 100-120 deg. F.

I have seen an impressive airbrushing demo where they painted a plastic car body with water-soluable paint and they dried in the matter of seconds using a hair dryer. Then they painted over that using another color without any nasty side effects. I don't recall the brand of that paint. Of course one has to be careful while using a hair dryer on a model. Especially if the model has some thin cross- section parts (like roof pillars on a car body).

As far as explaining why the same paint combination cracked on one model but not on another, there could be many variables. Things like ambient temperature and humidity, length of drying time between coats, etc.

Peteski