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Hi there, sorry if this is a dumb question but been having compressor issues. i wanted to check it isnt how compressors work before the retailer gets back to me about refunds and all that.

Basically if I set my release valve so it does not release any air, which for my Sparmax arism means 35psi. Within 2 seconds it has dropped down to 15psi. I will most likely never need 35psi but it would be nice if I get the pressure I set it to without having to wait for the pressure to drop to there, sometimes i might inadvertently release some paint at 35psi when i am really waiting for it to drop to
15psi.

any information or tips you can give to educate me would be greatly appreciated, cheers everyone.

Pressure drop is normal. Most compressors have a starting psi before you press the trigger to get paint out. It soon drops to whatever pressure that has been dialed in.(15-30psi or whatever it's dialed in for) I would suggest pulling back on your trigger without paint coming out and adjust the setting so you have the desired pressure you want when you are painting. Most compressors have an adjustment knob somewhere.

Hope this helps.

I did wonder about it having a starting pressure, as you called it.
but i always seem to get pressure far below the setting. but it does explain why in some tutorial videos there is a small time between the trigger being pressed and paint actually coming out, I guess they are waiting for the pressure to drop to the desired psi. Thanks for response it has enlightened me a little bit.

There shouldn't be a huge difference in the static pressure compared to the flowing pressure. Your compressor might just be a bit underpowered compared to the setting you are trying to use. Mine only drops a few psi between static and flowing, no where near a 20psi drop you are getting.

But either way it should only take a second at most for the pressure to balance out, I always start the air before the paint because trying to start the paint before the air is pretty much always going to make a mess because you can't know how much to pull back the trigger prior to starting the air

Does the compressor have a tank with it? It doesn't sound like it. I have a tank on mine, but when it empties and the the compressor is just running straight off the motor I can't sustain much pressure out of my little 1/6 horsepower compressor.

Well the pressure you set at is the pressure the tank is at. when you use the airbrush its going to release that pressure until the motor can fill the tank again.

if you want to set the right pressure you need, then after the tank is filled, hit the airbrush air only (without paint) then adjust the nob to the pressures you want while using.

like gundor said.

as for the time between trigger pressing and stuff. its probably to do more with preventing splatter from paint on the tip or guard.

alamandra wrote:
but it does explain why in some tutorial videos there is a small time between the trigger being pressed and paint actually coming out, I guess they are waiting for the pressure to drop to the desired psi.

Not really no, it just makes more sense to start the air before the paint for the sake of control. You turn on the air and then gradually pull back so you can find the point where the paint comes out otherwise you're liable to pull too far back and leave a puddle of paint on the model.

You should also cut off the paint when you finish spraying before you cut off the air, if you cut off the air before the paint you'll get a build up of wet paint on the needle and next time you go to spray it'll get blown off and cause a splatter.


Automatically Appended Next Post:

 Desubot wrote:
Well the pressure you set at is the pressure the tank is at. when you use the airbrush its going to release that pressure until the motor can fill the tank again.

The OP said this occurs within 2 seconds, so it's not the tank emptying, it would be that with the airbrush air closed the regulator was opened and it pressurised the air hose. So the air hose is at 35psi with stationary air in it. Once you open the airbrush valve, the air hose empties and the compressor can't sustain 35psi of flowing air, so it drops to 15psi.

At least that's my guess, from the sounds of it the compressor doesn't have a tank, if it does then there might be a problem with the tank not being sufficiently pressurised.

EDIT: If it only happens once, ie. the first time after you adjust the pressure, it might be that the regulator hasn't stabilised after you turned the knob, but if you spray and the pressure drops then stop spraying and the pressure rises again, it'd be what I said previously with the air hose being pressurised but the compressor not being able to sustain it.

Sorry I should have mentioned it is tankless, I am a complete beginner but it seems it is as AllSeeingSkink says and it just cannot maintain that pressure. It is not exactly a high end compressor so I was not expecting or needing big pressures, but it would be good if I had the option of going above 15psi. Which is the best I have managed to get this to sustain at.

Yeah I mean that's just my guess, how powerful is the compressor? What model is it? Maybe someone with a similar set up can tell you if they experience the same thing. I just checked on my 1/6 HP compressor, it will struggle but it seems able to sustain 30 psi if I leave the airbrush valve open, open the regulator as wide as possible but don't let the tank fill up. If I let the tank fill up I get a burst in the 50psi range for a while before it gradually drops back down to 30psi until I let it fill again.

So I'd imagine a 1/6HP compressor without a tank could probably sustain 30psi when airbrushing as well, unless you're using a particularly high-flow airbrush.

okay i shall elaborate on the gear im using, first up the airbrush is an iwata eclipse hp-cs im asuming the hp means high preformance. my compressor is sparmax arism. the information on the sparmax website is not the most detailed,it does say the working pressure is from 0 to 35 but nothing about the hp.

Hmm, that's a weird one, it uses a bleed valve rather than a regulator. Is that how yours is set up as well, with the bleed valve? I've never used a compressor with a bleed valve, the far more common method is to use a pressure regulator because a bleed valve will constantly be bleeding off air which puts more stress on the compressor, a regulator only flows when you want air.

Someone did a review of that compressor here...

https://www.youtube.com/watch?v=yjeWiQjuulM

It's hard to see the gauge, but to my eye it seems like with the bleed valve fully closed (not bleeding anything so all air goes through the airbrush) then it seems to pressurise to 35PSI with the airbrush off and then drop to 25PSI when the airbrush is being used.

It seems to me that using the bleed valve, if you slightly open the bleed valve (bleeding a small amount of air) then the pressure will hover around 30-35psi (being that the compressor cuts out at 35psi) and then when you actually open the airbrush itself, pressure drops further. So you have to set your bleed valve with the airbrush open otherwise it's going to be very hard to guess what the correct pressure is.

So try that, adjust the pressure using the bleed valve, but do it while the trigger is pushed down on the airbrush, see if that can get you to the pressure you want.

I would suggest a couple things:
Get a secondary pressure regulator 50psi or lower.
Get a flow control valve for the base of you airbrush (keep volume of air equal or less than the compressor produces).
Between those two items it could control your pressure drop a bit better but working distance may vary.
Remember that the "real" pressure to be concerned with is the "working pressure" during air flow: static does not mean much.
The difference is completely dependent on nozzle size or "back pressure" the airbrush creates.

"Proper" practice is to press down for air first then pull back to apply paint.
I have a 30 psi gauge I keep in my field of view to keep an eye on pressure drop before I start up my paint flow.
I usually see 20psi static and when I press down I drop to 15psi.
I have achieved interesting patina effects going down to 5psi since the spray becomes more blobby.

Many people swear by their tankless compressors, I have a 6 liter 2 piston GMC compressor that is pretty quiet and get zero pulsation..

 Talizvar wrote:
I would suggest a couple things:
Get a secondary pressure regulator 50psi or lower.

I'm not sure if a regulator would do the job on that compressor, it has a 35psi cut off and a 25psi cut in. That's a strangely narrow range for a compressor to operate it, which makes me think it's specifically designed to be used with a bleed valve rather than a regulator.

Normally with a regulator, you want the compressor to pressurise the upstream side of the regulator to a much higher pressure than the output side so that the regulator can function effectively as a step down, you might get fluctuating outputs if your input is also fluctuating at a pressure close to your desired output.

I guess you could just try it and see what it does.

I learned something since posting this question, it is the fact that the iwata eclipse range of airbrushes. Has a drop in self centering nozzle, which is fairly unique in airbrush land I am told. They seem to eat up a bit more airflow to get the same pressures as you might get with say an iwata revolution. So people considering an eclipse might want to consider something a bit beefier than the arism. I ended up treating myself to an Iwata Smart Jet Plus HandleTank Compressor. It is very unlikely that I will ever use its full power potential but it is never going to have to work very hard to give me what I do need. It is an investment and no exactly cheap.