Airbrushing pressure changes

You have a GOOD compressor. Try this if you haven't. Drill a pin size hole in the hose adapater-the brass reducer from the air outlet that you screw your a.b. hose on. This will act as a pressure release valve/help mantain a constant p.s.i. reading. I can adjust my p.s.i. down to almost "0" reading on my guage.

I do always give a short burst from my a.b. before I paint-just to make sure.

JMorgan

Thanks for your answer. I'll look into another compressor/tank combo. Mine (Campbell/Hausfield) you cant even adjust below 20 psi.

So don't give up get a smaller compressor if you have the $$ for it or learn to work around you current one by knowing what it going to do and be ready for it 

 

Regardless keep trying and things and knowledge will get better

Thanks for your answer. I'll look into another compressor/tank combo. Mine (Campbell/Hausfield) you cant even adjust below 20 psi.

It can a little but its such a small drop I wouldn't worry about it, I've never found it to be a problem and I'm sure better people with an airbrush than me would agree

Will the same phenomena occur with a compressor/tank combo that you mentioned?

You dont say what type of compressor your using so I'm going to give you a general idea of what can cause the problem. The air hose which connects the compressor to the airbrush can act as a miniature tank for the air. If you have a regulator on the hose when the air in the hose reaches the pressure you selected on the regulator it will be held at that pressure. When you first press the trigger on your airbrush this will let some air out so the pressure will drop a little. At this point the pump will start again forcing air into the hose, as the trigger is open it will get a little to much air then the regulator will catch up and get the pressure back to what you selected.

I know it sounds a bit complicated but I can say it happens with mine all the time, what I do as I have a duel action brush is let the air run for a few seconds then start the paint so the "pulse" of air your talking about is gone.

Hope that helps

Phil

JMorgan

Does anyone know what causes the pressure to change (right after you press the trigger) from low for a split second to higher and steady the next? The paint I used was thin and hte airbrush used was a Paasche H external mix. Thank you!

Your description fits the working of a poorly designed pressure regulator and its pressure port.

For the use of airbrush, the pressure setting provide a measure of the driving (pumping, pushing air) potential. It is most accurate to measure the static pressure when there is no flow. If your compressure has a diaphram type regulator, the knob will privide uniform, multiple turn adjustment that is linear in action. The pressure port should be a very tiny, 1/16" or so, hole connecting to the pressure gauge. The pressure reading may drop slightly, 0.2-0.5 psi when you push the trigger. The reading should be steady.

Some of the cheap regulator use a simple orifice or a gaping hole of 1/4" or larger in the pressure port or both to save cost. Effectively, the gauge sees partial dynamic, partial static pressure. It may result in what you see in your compressor. Because the dynamic pressure is NOT a constant of the pressure setting, the user lose the reference value.

A perfect pressure reading will require a 2-stage regulator like those you see in a torch setup. But it is too expensive and not really necessary for a hobby compressor. I have an old regulator from TCP Global from 8-10 years ago, it works very well. I bought a new regulator at Ebay out of couriocity last year, and the adjustment was coarse and the reading fluctrates. Both costed less than $20.

Below is a picture of my old, good working regulator. I replaced the pressure gauge with a large face one of 60 psi full scale. The setup allows me very accurate and fine adustment of pressure when experimenting with new paint and mixing ratio.