This may be a stupid question but i figured i would ask. Ill set the air pressure on the regulator on my compressor at say 20psi but when i spray the pressure shown will drop to around 14-15psi and stay there until i stop spraying. then it will rise back up to 20psi. Is this normal? If it is, if i want to spray at 20psi do i pay attention to the initial set pressure or the one that actually shows while i am spraying? I think i just confused myself now

Dave,

Does your compressor have a tank or is it a tank-lees diaphram design?

With a tank, the pressure setting should be the actual constant pressure that's fed to your airbrush. The tank will have air in it at a higher pressure, but the regulator should only allow air out at the set pressure - here 20psi.

If the tank pressure drops below that (20 psi), then the pressure at the A/B will also be lower.

If your compressor is has a tank, it could be that the tank is too small and doesn't hold enough air to feed a constant 20psi to your A/B when in use, or the pump isn't building up enough pressure, or the regulator is broke.

However, if the compressor and regulator are working and the compressor has the capacity, then the setting (20 psi) on the regulator should be what's coming out of the A/B.

With a tank-less design, the regulator actually controls the maximum pressure allowed, but if the pump doesn't put air out at a level ABOVE that normally, then as soon as you hit the trigger on the A/B, the pressure drops to the pump's normal output (here 14-15 psi as restricted by the A/B) and that's your normal, constant MAXIMUN AVAILABLE pressure with that particular A/B.

When the regulator is showing 20 psi, it's doing that because the A/B valve is closing off the air flow. In this case, the regulator will only control pressure at LESS than the pump's normal output (when hooked up to your A/B with the trigger ON). That means that you can control pressures at or LESS THAN 14-15 psi, but not above that pressure.

It's probably a matter of the equipment you're using and not that something's not working right. The compressors and regulators are generally pretty durable, so the odds are that they're working OK.

HTH,

Mine does the same thing Dave. I use a tank compressor with a regulator at the compressor set to about 80-100psi, and another regulator closer to the airbrush which is the one I adjust.

I adjust the initial pressure while spraying (empty cup)...so using your example if I wanted 15psi then the regulator would read 20. Since this is only for my reference to dial in what I prefer, I find it works (correct or not). Hence, what I consider 15 psi others may consider 20 psi. But they're only numbers, and I use what works at the time :-)

When cleaning the brush, I use the regulator pressure, 40psi in my case.

My A/C does basically the same Thing. I set the valve to 20 psi, but it drops to about 18 psi when is start to paint with my air brush. It's consistent time and and time again. I just figure that it's reading the pressure up against the shut gauge, but once the valve is opened on the air gun, the pressure drops to what the flow really is.

So .. when a builder says "I spray Model Air at 20psi" Does he/she mean 20psi before or after the airbrush button is pressed?

My compressors, tank and tankless, do the same thing at the regulator gauge. I do the same thing as James, basically. I adjust my pressure with the airbrush empty and the trigger open. If I say I shoot at 15 PSI, that is how I'm referencing it.
This becomes especially important if I'm using my .2mm airbrush with a crown cap to shoot hairlines at 6 PSI!

Great question, glad you guys answered it as I have been wondering the same darn thing for a long time now.
So, for finer detail, you usually use a lower PSI and for general work, you can use 20 or 30 PSI, correct?
Learning to airbrush has such a curve when there is no one to actually teach you about all the little things!