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Airbrushing Nail Polish - buildup problem


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#1 rhs856

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Posted 29 May 2012 - 05:10 AM

I've been messing around a little with nail polishes and have had the same problem each time: After mixing the paint 1:1 with lacquer thinner and spraying it through my Iwata at around 30 psi, there is a powder-like buildup (not orange peel). It looks like little round grains of sand. It doesn't appear on panels that I'm currently painting - meaning that if I'm painting the driver's side, the buildup might happen on the roof or trunk, but not the driver's side.

I'm sure it's overspray drying on the car, but I don't know how to correct it. Anyone have a similar experience or hopefully a solution?

#2 Fat Brian

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Posted 29 May 2012 - 06:53 AM

A quick way to test would be to only paint a small part of the body and then let it dry. If you don't get the grianular texture on the small area then its overspray, if you do it has to be something in the paint. If it turns out to be in the paint I would get a different brand and see if happens with it.

#3 rhs856

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Posted 29 May 2012 - 07:52 AM

A quick way to test would be to only paint a small part of the body and then let it dry. If you don't get the grianular texture on the small area then its overspray, if you do it has to be something in the paint. If it turns out to be in the paint I would get a different brand and see if happens with it.


So if it's overspray, how can I fix it? is my pressure too high at 30 psi?

Edited by rhs856, 29 May 2012 - 07:53 AM.


#4 Nitro Neil

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Posted 29 May 2012 - 08:45 AM

Yeah, turn the gun down. I spray at 15 psi, but there are some variables to consider.


Thicker paint needs more air pressure

Siphon feed needs more air pressure that gravity feed.

You may also have the wrong size needle/orifice for the paint you are using.

With a 1:1 mix of paint like that I would turn the gun down to 15-20 psi with the gun halfway open.

Try spraying from different distances to the piece too. You have be too close or too far away.

And also remember, with an airbrush lots of light coats works better than fewer thick coats.

It took me a while get comfortable with my airbrush, but now that I am, I wouldn't think of going back to rattle cans.

Edited by Nitro Neil, 29 May 2012 - 08:54 AM.


#5 CadillacPat

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Posted 29 May 2012 - 11:16 AM

Lacquer Thinner is not a universal thinner.
Have you tried using Nail Polish Thinner?

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#6 Art Anderson

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Posted 29 May 2012 - 02:33 PM

I've been messing around a little with nail polishes and have had the same problem each time: After mixing the paint 1:1 with lacquer thinner and spraying it through my Iwata at around 30 psi, there is a powder-like buildup (not orange peel). It looks like little round grains of sand. It doesn't appear on panels that I'm currently painting - meaning that if I'm painting the driver's side, the buildup might happen on the roof or trunk, but not the driver's side.

I'm sure it's overspray drying on the car, but I don't know how to correct it. Anyone have a similar experience or hopefully a solution?


OK, a simple answer here: What you are experiencing is overspray that is drying in mid air then being blown onto surfaces around the edges of the panel you are painting. I found, probably 35 years ago, when I was airbrushing automotive lacquer on stock passenger car bodies. The overspray was curling around the back of an old '59 Chevy (SMP) body, looking for all the world like dust buildup from driving the car on a gravel road! Not good.

Here's how I solved the problem. You say you are thinning fingernail polish only 1:1 with lacquer thinner? Fingernail polish, often called "nail enamel" is in reality lacquer, not enamel in the sense of say, Testors or Modelmaster, which are true enamels, but lacquers thinned only enough for hand brushing, so you are dealing with very thick consistency, which takes a lot more air pressure to spray through an airbrush.

In attacking this problem in the middle 1970's, I came up with the idea (prolly not my idea alone, but I did it on my own back then, there being no model car magazines to publish articles on painting at the time) of thinning the lacquer to approximately the consistency of 2% milk--this is an "eyeball" thing, there really can be no set formula, given that the consistency of automotive lacquers and even nail polish is very inconsistent, no two bottles of FNP seem to be the same consistency. Thinned as I describe, when you shake the mix up in a glass jar, you should see the thinned lacquer sheet down the inside of the bottle, looking very much like the way 2% milk "sheets" in a very semi-transparent way down the inside of the glass as you drink it.

Now, thinned this much, you don't need anywhere near 30psi to airbrush the stuff: So, cut back the airpressure to the airbrush to the point that it will not spray, then gradually open the pressure regulator until the lacquer just begins to spray, then adjust the material control (paint mixture) at the front of the airbrush to get a spray pattern about 3/8 inch or so, with the surface to be painted no more than say, an inch from the surface. The final psi you come up with may well be only 10-12psi, but by moving the airbrush in close as I point out, what you will have is in effect, a miniature spray gun with a miniature spray pattern. Of course, at such a low pressure, there will still be overspray, but it will be minimal, and a quality airbrush will still atomize the lacquer very finely indeed. And you will not see the dusty overspray you describe.

With a little bit of practice, you should be able to get a very nice finish using this technique, I have done all my model cars for the past 35+ years in this manner, and the real side benefit is that you can get maximum color coverage with minimal paint thickness, meaning that surface details tend to really "pop out" at you, rather than just being "softened up" by a heavy coat of paint.

Also, use the same technique when you apply primer--rattle canning primer will simply negate what you might achieve with color coats sprayed on as I describe; then polish the primer to a satin sheen before applying color coats. As a general rule, I seldom have to use any of the abrasive "polishing" cloths from a MicroMesh Polishing Kit for anything more than just touching up a small area of fine "orange peel" in areas I can't really reach with the airbrush spray pattern (under the lip of a "59 Chevy is a very good example of what I'm talking about here!), mostly going directly to the flannel cloth and fine polishing compounds.

Give this some thought, then try it on a test body, even plastic spoons, and see if it doesn't do a much better job for you.

Regards,

Art Anderson

#7 Chief Joseph

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Posted 29 May 2012 - 04:20 PM

That's an excellent write-up on the subject, Art!

#8 Greg Wann

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Posted 29 May 2012 - 04:44 PM

I would try to find an actual nail polish thinner. There are SALLY BEAUTY stores here that sell an 8 ounce bottle for about four bucks. Oddly, big box stores sell all kinds of remover but not thinner. There are some pretty cool colors in nail polish. Somtimes you can get it cheap too.

#9 CadillacPat

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Posted 29 May 2012 - 11:54 PM

I still suggest you try using Nail Polish Thinner instead of Lacquer Thinner,

You say you are shooting at 30 psi so you must be way back from your model allowing much of your paint to dry in mid air before reaching the surface, causing your sandy buildup.
If you were shooting at 30 psi from close up , as you should be, you would be loading up the model with paint.
Crank down the air presure and move in close.

There is a reason they call it "laying down paint", because you actually lay it down close to the surface, making overlapping passes to effect a wet coat.
Most of my work is done with 20-25 psi from no more than two inches from my DieCast.

Lacquer Thinner is a very dry chemical and could itself be part of your sandy overspray problem.
Use the right products for the right paints, check out Nail Polish Thinner.

CadillacPat

#10 rhs856

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Posted 30 May 2012 - 07:26 AM

Thanks to everyone who posted - I'm looking into nail polish thinner and will definitely try lowering my pressure. Art, your explanation is incredible - it confirmed my suspicions and made me laugh to realize that I'm having the same problems as a person who actually paints 1:1 cars.