Airbrushing help

[astrosa]

OK, figured I'd post this and see if anyone has specific advice for dealing with metallic (i.e. silver) paints.

I'm doing fine with regular flat-finish paints, both acrylic and lacquer, but the metallic ones are always a headache, with no exceptions. Unfortunately, this is a huge problem for me, since models of Amtrak and MBTA equipment usually need to be painted a stainless steel or flat silver color. In this case, I was painting two models with Polly Scale's Flat Aluminum. Normally I stick to acrylics because they're easy to clean up, and I do tend to make a mess every time.

Incidentally, I've seen it mentioned in a few modeling articles that metallic paints are hard to work with, but none of the airbrushing "how-to" articles have mentioned metallic colors. I follow the tips in those articles and get great results using normal paint - last night I used a flat gray acrylic to prime some models, and the finish came out perfectly smooth and even. But as soon as I loaded the Flat Aluminum into my airbrush today, all hell broke loose.

I'm using an Aztek 3000S, which is very similar to the more-common A470 and such. It's double-action, internal mix, and like I said, I usually get great results using normal colors. I have a compressor that puts out around 40 psi, though I don't have a regulator for it. I'm thinning the metallic acrylics the same way I thin flat colors, using about 25-30% water, and everything else is the same. Yet as soon as I pull back the trigger, I get a sputtering cloud of paint at a much higher flow rate than with flat colors. It's very hard to maintain consistent flow, and trying to back off the pressure results in nasty spattering, leaving big bright spots on the model.

To compensate for the high flow rate, I have to spray from at least 6" away to avoid pooling and running. In that case, I can lay down a very thin coat that is reasonably even, but it looks terrible because the metallic pigment seems to be reflecting the light unevenly. I suspect that the paint is drying before it hits the surface. Spraying closer to the model causes the paint to go on wetter, but it's also thicker and much more uneven. On a model of a smooth-side Budd coach, I got the sides to look half-decent, but the roof got some spatter that is especially noticeable thanks to the corrugations. On an F-unit that I was also painting, I started off spraying closer, and the result was a thick coat that dried unevenly, so you can still see the spray patterns I was using for each pass.

It seems like my problem would be solved if I could just spray at a lower pressure, but when I try to do that, I either get no paint at all, or I get big spattering droplets.

Needless to say, it's extremely frustrating to have had these models look so beautiful in primer, and so awful now that they've received their base coat. I'm getting really tired of having to strip models and start over again...so I wish someone could finally explain what specifically needs to be done different with metallic paints. In other words...why do I have no problems with flat colors, but zero success with metallic ones?

Thanks,

Alex Stroshane

[jwb1323]

I've had little problem with Floqui metallic paints. I use their various Silver and Platinum Mist, and Brass, fairly frequently with good results. I thin with lacquer thinner and use Glaze in the same proporations as with other Floquil colors.

From what I hear, acrylics need a higher pressure in many cases. I have the same situation, just a compressor with no regulator, and it probably doesn't supply a high enough pressure to get the best results with acrylics. But I'm old enough to be a little set in my ways with Floquil solvent based paint anyhow.

I used to use a double-acting airbrush, but more recently use a cheap Badger. Robert Smaus, a very good modeler, made the point in one of his articles that for most model railroad use a cheap single-acting airbrush is good enough. Lots easier to clean and lots less to go wrong than a double-acting.

So I would experiment with different brands of paint as well.

[pdt]

I'd have to agree with John here on the single action vs. double action airbrush (though that doesn't solve your problem). If you're spraying colors intended to cover an area and aren't interested in achieving any special effects, there's no need for a double action brush. Just my opinion on that one.

Anyway, have you tried thinning with something other than water, like alcohol? It might make a difference for you, since alcohol has less surface tension than water and is easier to mix into a solution. If you're getting clogging, which the spattering might indicate you are, you may need to thin a bit more.

I've never used acrylics (well, the old Polly S acrylics don't count - different generation of paint), so I'm not sure how they behave vs. solvent paints. But, with solvent paints, you generally need to thin a bit more than usual to get the gummier paint vehicle to dissolve into the solvent. I don't know why metallic paints tend to be gummier than regular paints, but that's my experience.

Good luck.

[astrosa]

Thank you, gentlemen...that's a start.

I actually used to use a cheap single-action, external mix airbrush - the Badger 250. I was convinced that it was the cause of my troubles, since it seemed like I had so little control over paint flow and pressure. I'm sure that with internal mix, single action would be enough, but I wanted to eliminate the quality of my instrument as being the source of the problem. I'll be doing some weathering too, so I like the extra controllability.

One of the neat things about the Aztek series is that you can actually use them as if they were single action, which I frequently do. There's a dial that lets you preset the opening of the needle, so just pushing the trigger will spray the same pattern every time. If you happen to decide you need more flow, pulling the trigger back still works. It basically just re-zeroes the needle opening so it defaults to being partially open instead of closed.

Anyway, Andy Sperandeo frequently mentions in his articles that he uses a 50/50 mixture of alcohol and water to thin Polly Scale acrylics. I've tried that before and didn't notice any difference, but maybe thinning with alcohol alone would have an effect.

It turns out that my Budd coach came out well enough to be workable. The Flat Aluminum dried a lot brigher and shinier than I expected, which just means I'll have to weather it down even more - the prototype I'm modeling had smooth sides instead of fluted, so Amtrak painted them whereas most Budd cars were bare stainless steel. By the time they were retired, the paint was peeling pretty badly, so it's not like I need an impeccably smooth finish.

The F-unit is another story, though...looks like I'll probably have to strip it no matter what, but when I try it again I'll use Floquil Platinum Mist, since there's one more car that needs to be that color anyway. Hopefully I'll have better luck with the lacquer...and I may investigate Badger's ModelFlex line, which I hear are pretty much thinned as they come from the bottle.

[pdt]

That Aztek brush sounds pretty cool. I've always used Paasche brushes since I was in high school, so it's hard for me to relay experience beyond their designs. I used to paint caricatures at the mall when I was in college, so I really learned most of my skills there. But, I also learned that it would have been nice to have a single action to spray a smooth coat of paint over a large area. So, when I paint model trains now, I go with a single action brush.

I've seen an Aztek brush before, but it was years ago. Don't they have plastic tips? How durable are they? Are they forgiving when you've been painting for hours? My Paasche brushes are pretty much indestructible, so aside from habit, I've never needed to replace them.