# optimal psi for model airbrushing



## Rocket

I'm about to purchase my first air compressor for model building. It appears that each one has different psi ranges. Do I really need one that shoots 90 psi??? What is the average psi for model building? Is it more in the 35-40 psi range?


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## djnick66

Rocket said:


> I'm about to purchase my first air compressor for model building. It appears that each one has different psi ranges. Do I really need one that shoots 90 psi??? What is the average psi for model building? Is it more in the 35-40 psi range?


You really don't "need" much over 25 PSI. But there are quite a few things to consider...

Different airbrushes work optimally at different pressures. You want to get a compressor that is suitable for your brush/brushes. For many years I used a small, fixed pressure, piston compressor. I had a WR Brown model, but its about the same as "airbrush" compressors sold by Paasche, Badger, etc. They are not adjustable (or only in very coarse degrees) and put out a fixed pressure. Now, I use a small Campbell Hausfeld tank compressor I bought at Wal Mart. With a moisture trap, the compressor was under $100. It is fully adjustable. I only use it for airbrushing, so its always operating at the low end of the pressure scale, but if I need I can pump a tire, run small air tools, etc.

When using the old piston compressor, its fixed pressure seemed okay for most Badger type brushes. I use the 200 a lot, and had no real problems with it working. On the other hand, it seems like Testors/Aztek brushes, with their spring loaded plastic nozzles and rudimentary crimped tube air valves inside, need much more pressure. My A4305 brush would not work at all with the basic piston compressor as the compressor output was not enough. Many years later, I bought a Tamiya/Iwata High Grade, Extra Fine detail brush. This also did not operate well on the piston compressor. This time the compressor put out too much air! When not spraying the pressure would force air through the valve and cuase paint to bubble up and collect in the tip. When spraying, the paint would stream out like a hose and splatter badly.

So, the Badger brushes seem to operate well around the 12-18 psi under load range. Azteks seem to do better in the 25 psi range. My Tamiya/Iwata brush is optimal around 5-8 psi. Using an adjustable compressor solves ANY problems with pressure.

Different paints also require different air pressures. You cant spray every paint, on every model, at one constant pressure. Acrylics can be thick and don't make as fine of a mist as solvent based paints, and you may need a little more pressure. Likewise, metallic enamel paints may need a little more pressure, but thinned, flat enamels can use less pressure. TO paint small, thin, lines you use less pressure. Paints like Alclad need very little pressure (under 10 psi). You just want to barely mist those on. But if you are spraying something big like a 1/48 B-29 you might need a big needle/nozzle on your brush and somewhat higher pressure.

So get a compressor that is versitile and will work with your brush/brushes.


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## ajmadison

Hopefully I'm not contradicting what was already written, but whatever you do, be certain to get a compressor with either a built in, or is capable of having attached, a pressure regulator.

I have the previously mentioned Aztek airbrush, and I use it under a variety of pressures. If I'm shooting a glossy base coat, I'll crank the pressure up to 20 Psi. If I'm shooting details, then I thin the paint down to skim milk consistency, and shoot around 12 Psi. 

My current setup is pretty crude, the regulator was a unit I got from "The Home Depot", and the airbrush stops working if I try and crank the pressure down to under 10 Psi, but I've always believed that's due to the crudity of the regulator I'm using. Its actually marked at 5 Psi intervals, going up to over 100 (though the compressor attached to it will never make more than 30). A regulator allowing finer adjustment would be better, but it would be also more expensive, and what I found didn't keep me from doing what I wanted.


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