Scalecoat I and II: Airbrush Mixture and Air Pressure Needed

[ai5629]

I was planning on airbrushing some N scale oxide red Conrail gondolas this week, and I am going to use Scalecoat II paint and thinner.  I have not painted anything in two years, so I do not recall the mix of paint to thinner or air pressure to use.  I was thinking it was 1 part paint to 1 part thinner and about 15 psi.  To complicate matters, I seem to recall something about red paints needing to be thinned a little more due to their thickness.  I also want to paint some Conrail flatcars with Scalecoat I, and have the same questions.  I did a search, but could not find anything.  Thank you in advance for the help.

Jeff

[ai5629]

I have answered my own question.  This used to be on the Weaver web site, but only recently appeared on the Minute Man Models web site. 

http://www.minutemanscalemodels.com/v/vspfiles/Colorchart/ScalecoatColorChart.pdf

[peteski]

I have answered my own question.  This used to be on the Weaver web site, but only recently appeared on the Minute Man Models web site. 

http://www.minutemanscalemodels.com/v/vspfiles/Colorchart/ScalecoatColorChart.pdf

I'm really bad when it comes to recording air pressures and thinning ratios. Every time I airbrush I adjust everything until it works.    I sometimes even change the air pressure and nozzle opening (I have Badger 200). I reduce the paint flow and pressure when I try to get the tight corners or other recessed areas painted. Then I crank up the pressure and paint flow for larger flat areas.

I also highly recommend to test your settings on a plastic spoon before painting your model. I do that a lot. Spoons are cheap and disposable. If the settings give me good results on the spoon, I then move onto painting the model.

[C855B]

I had a recent situation where I ruined a project applying Scalecoat II, so am spending a lot of time testing on scrap material before deciding on mixture, airbrush settings and pressure. Just this evening I may have landed on a good balance - 3:1 reduction (that is, 25% thinner), 30 psi, and 0.4mm nozzle. It went down the best I have seen yet with Scalecoat. I'll know more in the morning when I remove the masking tape and check the ridging.

But this is what is working for me at the moment and may not be ideal for your setup. There are a lot of variables to consider up to and including ambient humidity. I would suggest that you use the Minuteman info as a starting point only and test on disposable or scrap material similar to your project, such as Pete's plastic spoon suggestion.

Pete, I think what happened with the C855 disaster was pressure too high (40 psi), paint too thin (2:1) and too large of a nozzle (0.8mm). These worked fine for Tru-Color, but not Scalecoat.

[peteski]

Pete, I think what happened with the C855 disaster was pressure too high (40 psi), paint too thin (2:1) and too large of a nozzle (0.8mm). These worked fine for Tru-Color, but not Scalecoat.

That sounds like a reasonable analysis Mike.
As far as the air pressure goes, I rarely go above 20 psi for any kind of paint.  For small items like N scale shells I keep the nozzle  about 3-5" away from the painted surface. Sometimes even closer when I need to get into tight spots.

[nkalanaga]

Off topic, but still Scalecoat related, is there any advantage to using Scalecoat I on metal?  They both have the same solvents, just in different proportions.

[C855B]

I can't authoritatively answer this question, but you're due a response. It is my understanding that the more aggressive solvent blend in SC-I results in a better bond regardless of what's underneath. SC-II was apparently created because the solvents were too hot for plastics. I guess sort of like a diet version of the original, where the original always tastes better.

Since I'm in paint testing mode at the moment and have had both SC-I and -II on the shelf I thought I'd try a comparison. Turned out my SC-I is so old it has separated and skinned-over, so not only is it not going be reliable as to composition, I think it is the old pre-Weaver, pre-Minuteman formula, and IIRC the volatiles mix has changed since then.

[nkalanaga]

I have three bottles of the old (1970s) SC, two SC I and one SC II, and haven't used them in probably 30 years.  I just looked, and none of them will mix by shaking either.  I guess it does have a shelf life!  No great loss, as they didn't work for brush painting, and I don't have an airbrush.  Brush painted it took a week to dry enough that dust wouldn't stick to it.