Airbrush air pressure differences

[Defiant911]

I have two airbrushes, one has a 0.5 needle and the other a 0.35 needle.
when connected to the same air source the air coming out of the 0.5mm is significantly more . I guess this is due to the large needle / hole but I’d ha e thought rather like a water hose pipe the smaller hole / needle would increase air pressure? I find my paint spray pattern from my 0.35 needle very narrow, too narrow to be honest. Something doesn’t seem quite right. Perhaps someone can clarify what I should expect from these two basic needle differences?

carl

[Guest]

Hi Carl, I know much more about spray guns than I do airbrushes, but since the technology is similar I'll try and help, since you've had no other replies.

Firstly the sizes you quote are for the fluid outlet size of the brush, so don't necessarily correspond the how much air it puts out. As a rule though you'd tend to find that a larger needle size would also use more air. That's because you move up to a larger size to get more fluid output (or to spray a more viscous product), so you would need extra air flow to go along with that. And note I say flow, as it is very different to pressure.

Also unless they are exactly the same model of airbrush they can't be directly compared either, as one model may use more air than another, regardless of needle/nozzle size.

As an example, I have several spray guns with a pretty standard 1.3mm fluid nozzle. Some of these consume ~9 CFM (cubic feet per minute) of air, while some need nearer 14 CFM. Some put out a narrow cigar shaped pattern, some a wide flat strip. Some put out a medium amount of paint, some hose it on. All from the same nozzle size. So imagine how varied things can get once you start changing that size too.

What I'm trying to get at is there are many more variables than the size of the nozzle which will affect how an airbrush sprays. A 0.3 brush from one manufacturer might use more air, put out more paint, and give a wider pattern than a 0.3mm from another brand (or even a different model from the same brand). If you find your 0.35 brush has too narrow a pattern (most people usually complain about the exact opposite, and want a narrow, tight pattern!), then try playing around with the pressure settings, distance from the object, thinning ratio of your paint etc. If you still aren't happy then see if you can try out a different 'brush and see if that suits you better.

[Defiant911]

T

Hi Carl, I know much more about spray guns than I do airbrushes, but since the technology is similar I'll try and help, since you've had no other replies.

Firstly the sizes you quote are for the fluid outlet size of the brush, so don't necessarily correspond the how much air it puts out. As a rule though you'd tend to find that a larger needle size would also use more air. That's because you move up to a larger size to get more fluid output (or to spray a more viscous product), so you would need extra air flow to go along with that. And note I say flow, as it is very different to pressure.

Also unless they are exactly the same model of airbrush they can't be directly compared either, as one model may use more air than another, regardless of needle/nozzle size.

As an example, I have several spray guns with a pretty standard 1.3mm fluid nozzle. Some of these consume ~9 CFM (cubic feet per minute) of air, while some need nearer 14 CFM. Some put out a narrow cigar shaped pattern, some a wide flat strip. Some put out a medium amount of paint, some hose it on. All from the same nozzle size. So imagine how varied things can get once you start changing that size too.

What I'm trying to get at is there are many more variables than the size of the nozzle which will affect how an airbrush sprays. A 0.3 brush from one manufacturer might use more air, put out more paint, and give a wider pattern than a 0.3mm from another brand (or even a different model from the same brand). If you find your 0.35 brush has too narrow a pattern (most people usually complain about the exact opposite, and want a narrow, tight pattern!), then try playing around with the pressure settings, distance from the object, thinning ratio of your paint etc. If you still aren't happy then see if you can try out a different 'brush and see if that suits you better.

Thanks for your reply Andy,
as you say there are probably too many variables when not comparing identical brands in particular. Having done some experimentation since posting I think a lot of my issues is with viscosity of the paint. The thicker paint goes through the 0.5 without problem and with good dispersion but when the same paint viscosity is put through my 0.3 it barely got out the nozzle. After I diluted it down plenty I managed to get the airbrush spraying in a more even pattern. They are clearly two different beast and need very different approaches to achieve good operation.
carl