Painting a balsa model

[Sam Longley]

This may seem mad but I enjoyed Ron Gray's posts about laminating film for covering. So much so that I went & bought a 150 *600 roll of gloss for myself.

But of course it is no good if the plane does not have any colour & paint is not cheap. I want blue & cream & with a 60 inch wingspan model that is a lot.

So whilst wandering round Wicks, I came across emulsion sample pots at £2.25 each. Plus hundreds of colours.

So why not give it a go.

First emulsion on balsa remains soft. So once applied can be sanded really easily & fills the grain well. But then the colour goes so further applications are required. Then because it is soft the film pulls away.

So how do I get the film to stick?

First idea was to give it a coat of thinned PVA. That worked better but the PVA spoiled the colour & I am not sure that the PVA will not pull off the emulsion layer over time.

 

So my latest idea- & I may have cracked it-  is 2 parts emulsion, 11/4 part everbuild 502 PVA adhesive ( Because that is what I have), 5 parts of water. Then mix it really well in a glass jar. & I mean mix really well. Then 2 coats applied to a balsa test piece with 24 hours drying time. Light sanding between coats. Then a final sand with carrot paper.

Then the laminating film applied at 192 degrees

I used a desert spoon for the measure & that creates quite a lot of paint so one does not need lots of emulsion. The Everbuild PVA that I had is very thick, hence a lot of water. But that makes the mix go further. I actually ended up using some magnolia left over from painting my house & I expect others may have some emulsion to experiment with rather than buy any specially for a trial.

 

It seems to work & if it does I have a cheap supply of hundreds of colours. If anyone else wants to have a go they may improve on that or rubbish it then I would like to know please

Thanks

Sam Longley

 

Edited January 20 by Sam Longley

[leccyflyer]

That's an interesting technique. If you go to B & Q with a sample colour they will scan it for you and you can get a sample pot, in a variety of finishes for £4, which would paint several funfighter sized models. You are essentially making your own Solarfilm there, with an infinite choice of colours. One slight concern for me would be that painting a water-based emulsion directly onto balsa there might be a large absorption of heavy paint into the surface. Some form of sealing the surface first might be worthwhile. I'll be really interested to see the finished result on your model. 

[Basil]

13 minutes ago, leccyflyer said:

That's an interesting technique. If you go to B & Q with a sample colour they will scan it for you and you can get a sample pot, in a variety of finishes for £4, which would paint several funfighter sized models. You are essentially making your own Solarfilm there, with an infinite choice of colours. One slight concern for me would be that painting a water-based emulsion directly onto balsa there might be a large absorption of heavy paint into the surface. Some form of sealing the surface first might be worthwhile. I'll be really interested to see the finished result on your model. 

What about finishing the balsa with sanding sealer, gives a great surface and should take water based products as it has some polarity. Thats what we used to use to ready the balsa for some kind of finish.

Bas

[Ron Gray]

Try applying the paint to the adhesive side of the lam film, let it dry then apply the lam film. TBH some paints work, some don't but give it a try because that is really making your own coloured covering film.

[Sam Longley]

One has to remember tha emulsion is soft. So the PVA is needed to bind it to a hard finish. Then when the lam film is applied the paint does not pull away from the substrate. The application of the PVA & water also has the affect of filling the balsa rather than just the paint soaking in on its own. The water evaporates away thus reducing 60% of the applied weight of the mixed paint. The PVA seals the surface.

At least that is how I see it.

I will try painting the lam film but holding large areas out flat & applying 2 coats is difficult. OK with a smaller area though if it works.

 

Clearly there is room for experimentation. Hence my post.

[Futura57]

I'm currently in the process of finishing a foam model (XPS foam sheet and Depron sheet) with Matt finish laminating film, first ironed directly on to the foam (at around 100°C) then the film is hand painted on top with Wickes and B&Q Matt match pots. I figured the paint would adhere better to Matt film rather than gloss. The results are ok, but the paint does lift in places when using masking tape. Frog tape is less sticky and better but still lifts the paint in places. Results were far better when I tried a Halfords white spray primer on a test area, but I wanted to try the emulsion paint option. Perhaps spray primer then emulsion would fair better. I have done an almost entirely hand painted job. It remains to be seen how resilient the final finish is. I could always over coat with thinned PVA or perhaps acrylic spray clear lacquer or some such to maybe give a tougher satin or gloss finish. I'm not too bothered because it is a foam prototype model so it's not critical. I will post some pictures soon in my Strange Quark topic when I'm done.

[Don Fry]

Future, I use Matt doculam. To get water based paint to stick my experiments suggest it needs a scrub with solvent after covering to get rid of (I assume) a manufacturering  coating. Not my game, but there is a whole science based on altering the surface of things to allow coating to stick, or not stick. 
I find acetone, or 100% isopropanol works. There may be better solvents out there.

Thank you Sam, I’ll try a bit of that, I’m just doing a new big hack, and I’m going for a semi naked wacky look. 

Edited January 21 by Don Fry