Paint Exploration - A Digression
Well, with help from
@Jack Jäger and
@AllanKP69; some online research and a battery of tests of the things I have on hand I now have a painting process that suits me. There were no big surprises, in fact no radical changes to my painting methods on plastic. However, before today I was trying out different ideas in a random sort of way and confusing myself rather than learning anything. A day's
systematic trial has put my mind at ease about the best way for me to paint on wood. That's not to say I won't do it differently and better later on but for now I'm content.
It was quite fun to experiment. I always enjoyed high school science.
I drew a grid to organise my variables. The first one was whether to seal the wood first or not so half of my tests were done on smooth bare wood and half on pear wood treated with a coat of sanding sealer and a coat of shellac. I let this dry well and rubbed each layer down with 0000 wire wool.
View attachment 477400
Then I tested four undercoat/primers. StyNylRez acrylic polyurethane surface primer, "for use on plastics, metals, woods, resin, various other substrates". This was my go-to primer on plastic models, usually sprayed on, but also brushable. I have a variety of colours to suit the final finish and tried white and pink. Acrylic gesso which is a similar substance but with ground marble (probably artificial nowadays) mixed in for gap filling - it's used by painters to prepare canvas and wood panels for use. and the fouth possibility was 'No Primer'.
Two sealer conditions times four primers equals eight lines of inquiry.
View attachment 477401
I have five paint ranges on hand and tested them all. Vallejo and Tamiya acrylic model paint - on plastic I'd always detail paint with a brush using Vallejo and airbrush Tamiya. The artist's oils I only ever used on figure models and for weathering. I didn't expect them to be useful but since I had them, they were tried. System 3 Acrylic is tube paint for artists. It's a cheap one, bought in a sale on impulse and not very good but since I had them... Finally Humbrol enamel which I've already used on this build. I've also used Vallejo. I didn't prime either and I'm not certain that I sealed the wood. Neither gave great results when used carelessly.
Two sealer conditions X four primers X five paints = 40 lines of inquiry.
View attachment 477405
Applying anything to bare wood was problematic.
All of the primers being water based, raised grain and when the fluff was sanded off there were holes in the coverage. The water on one side of the wood caused cupping, warping and bowing to the unsecured wood but this mostly straightened out later.
It was obvious that gesso is too thick for this use. I've used it as a filler on first plankings but it was hard to sand smooth. I'd forgotten that. It's got ground rock in it so as a filler and as a primer, it's no good.
Painting on bare wood, no sealer, no primer wasn't much use either. Oils soaked right through my 2mm pearwood, or at least the oil did. That would make drying time very long but more seriously, do I want linseed oil soaking through my planks and attacking the glued joints below? No thanks. Enamel and all the acrylics caused temporary cupping and the colours were dull and drab.
Shellac.
I've been reading about this remarkable old material. Have a look on Wikipedia, it's fascinating. Though it's organic, it's also a
thermoplastic substance. It's plastic! That's the stuff I'm so familiar with painting onto. A good sign.
It goes off in the bottle if you keep it for too long. The dry flakes last forever but once its dissolved in alcohol the clock is ticking. My sanding sealer has gone like sour milk because it's life-expired. Who knew? Not I? I'll buy some fresh tomorrow. Or send away for flakes.
The first coat should be thinned. I knew that last year but I had forgotten.
It's beautiful, smells reasonably nice, dries fast and is a wood finish in it's own right. It comes in many different shades depending on the tree that the beetles were feeding on.
The worst thing about it is that it makes the wood look so nice it's heartbreaking to cover it with paint.
Back to the Trials
Both colours of StyNylRez painted onto the shellac without a problem. There were two fish-eye patterns in one place. This is caused by the incorporation of microscopic particles of wax from the Lac beetles that get harvested with the lac flakes. It made no difference to the final paint finish but if you buy flaked shellac try to get a de-waxed product. I had abandoned the gesso by now so that was five tests less to do.
Generally, painting over shellac with no primer produced dull colours but no distortion of the wood. They may even be historically accurate colours but dull is just dull!
Pink Stylnyrez was just as bad with the five reds. However, different undercoat colours are sometimes surprisingly effective. Yellow paint is much easier to paint over pink primer and produces a much better finish. Painting yellow is usually quite tricky without this.
White StyNylRez over shellac made a smooth and receptive ground for the red paints. And here are the verdicts on the paints
The oils were found guilty of stinking the place out and bothering the dog's nose. They were also guilty of taking too long to dry and being a swine to clean up after.
The artists acrylic was guilty of not having enough pigment. Brushing it was nasty leaving brushstrokes everywhere even after two coats.
Humbrol Enamel was a co-defendent of the oils and was also sentenced to the storeroom for being stinky.
Two coats of Vallejo (and acrylics always need two thin coats) was cleared of all charges and declared the go-to paint of my modelling future.
There was a surprise verdict on the Tamiya acrylic paint. On plastic, it's always been a swine to paint with a brush because it dries so fast due to high alcohol content but here, it brushed 90% as well as the Vallejo. If ever I need to airbrush wood, I'll reach for the Tamiya and if I'm short of a colour in the Vallejo range, Tamiya will step in as a replacement.
SO, what I learned today was to turn my wood into plastic with shellac and then paint it exactly like I did on the last 200 plastic kits. Stynylrez first then Vallejo on a brush or Tamiya in an airbrush. Good to know and fun to find out.
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p.s. I'm sorry about this update. I think it's the most boring thing I've written since Third Year Chemistry homework.