Airbrush Pressure Question: Static or spraying pressure?

[chuck540z3]

I read here all the time about spraying whatever paint at, say, 20 psi. Is that the static (shut-in) pressure before you hit the trigger or the actual flowing pressure. Eg. In order to get 20 psi flowing pressure, you set your regulator at maybe 30 psi before hand.

Stupid question maybe, but I bet I'm not the only one.

[toadwbg]

I read here all the time about spraying whatever paint at, say, 20 psi. Is that the static (shut-in) pressure before you hit the trigger or the actual flowing pressure. Eg. In order to get 20 psi flowing pressure, you set your regulator at maybe 30 psi before hand.

Stupid question maybe, but I bet I'm not the only one.

Actually a good question, I was thinking along similar lines recently. I know we often use the static and flowing interchangebly even tho they are not the same.

If someone says "set to 20psi" that is no-doubt static. Depending on their airbrush and how open the trigger is you can have different results with the flowing pressure. There are several other small variables at play here as well.

I certainly have seen pressure drop as much as 5psi below static pressure when using my Badger 360 WOT (Wide-Open-Throttle) with very thin Tamiya Acrylics.

[Matt]

It could be either, but ultimately it doesn't really matter. There are so many variables involved in airbrushing that we can never really talk in absolutes.

If someone reports having a certain success at 20PSI, then all you can take away from that is a general idea. Even if you have the same model airbrush, the same paint type, the exact same thinner, the exact same paint/thinner ratio, you'de still need the exact same pressure regulator, gauge and probably even airhose and even then, you don't know how accurate that gauge is, so you could be +- a couple of PSI. And finally, even if you'de got all that identical, you'de have to handle the airbrush the exact same way. Same distance to the subject, same speed of movement, same trigger control.

I don't think I've ever looked at the actual numbers on the pressure gauge when painting. Its just something that comes by feel, based on what paint I'm working with and how thin I want to work it, based on how I'm about to paint (freehand shading is very different to just laying down some base colour).

There is no substitute for a 'test' spray before you start to fine tune. I start with an initial mix and pressure, have a test spray, then tune the pressure as low as I can get it and still get the right spray pattern. Occasionally I may adjust the paint mix if its too thin or too thick. I used to test on a sheet of paper, but the absorbency can be misleading, so I switched to old kits. Now I have a section of the work table that is so covered in layers of paint that it pretty much works the same as a kit surface.

Cheers,

Matt

[Bob Beary]

It could be either, but ultimately it doesn't really matter. There are so many variables involved in airbrushing that we can never really talk in absolutes.

If someone reports having a certain success at 20PSI, then all you can take away from that is a general idea. Even if you have the same model airbrush, the same paint type, the exact same thinner, the exact same paint/thinner ratio, you'de still need the exact same pressure regulator, gauge and probably even airhose and even then, you don't know how accurate that gauge is, so you could be +- a couple of PSI. And finally, even if you'de got all that identical, you'de have to handle the airbrush the exact same way. Same distance to the subject, same speed of movement, same trigger control.

I don't think I've ever looked at the actual numbers on the pressure gauge when painting. Its just something that comes by feel, based on what paint I'm working with and how thin I want to work it, based on how I'm about to paint (freehand shading is very different to just laying down some base colour).

There is no substitute for a 'test' spray before you start to fine tune. I start with an initial mix and pressure, have a test spray, then tune the pressure as low as I can get it and still get the right spray pattern. Occasionally I may adjust the paint mix if its too thin or too thick. I used to test on a sheet of paper, but the absorbency can be misleading, so I switched to old kits. Now I have a section of the work table that is so covered in layers of paint that it pretty much works the same as a kit surface.

Cheers,

Matt

What he said.

This actually is a great reply and really sums up a lot of what goes into airbrushing. It is a lot more art than science. And a LOT of PRACTICE.

Bob

[chuck540z3]

What he said.

This actually is a great reply and really sums up a lot of what goes into airbrushing. It is a lot more art than science. And a LOT of PRACTICE.

Bob

Thank you gentlemen, that info is what I was hoping for.

I adjust my compressor to a zone that just seems to work right with the enamels I always use and I really don't even know the exact pressure I'm using- it just works for me. With all the replies here that always yak about spraying at 18-20 psi (or something similar), I was a little worried that I might be missing something. Sometimes I use fairly high pressures of 40 psi or so with my Iwata, because the lower pressures just don't feel right for whatever I'm spraying. I also find that certain colors like flat black and flat white require a little more oomph to get them to lay down nicely.