Spray Gun air pressure.

[TriumphDave]

Hi,

I'm just about to order my cellulose paint and looked at the data sheet, it says gun pressure is 4 Bar, but every guide I've looked at people say set the pressure to 2 Bar.
I'm a bit confused as theres a big difference?

I'm an Instrument fitted by trade, so I checked the pressure gauge that goes on the spray gun at work and found it read 5 psi low, so if I set the pressure at 2 Bar (30psi) then the actual pressure will be 35 psi.
This might be nothing, I don't know how acurate the pressure needs to be. Plus I suppose this has to be expected when buying cheap items!

Thanks,
Dave

 

[Wendelspanswick]

I always set the pressure by 'feel', pressure too low and the paint doesn't atomise, too high and you get loads of over spray.
Plus the pressure needed is directly linked to the viscosity of the paint, the thinner the paint the less pressure required.

 

[Daz1968]

The pressure is usually determined by the spraygun spec for atomisation. My devilbiss is 2.0 bar but others vary. A small tweet sometimes helps to get a better finish but I never alter by more than a few psi

 

[brightspark]

I always set the pressure by 'feel', pressure too low and the paint doesn't atomise, too high and you get loads of over spray.
Plus the pressure needed is directly linked to the viscosity of the paint, the thinner the paint the less pressure required.

i do the same. a small test piece on a 1 gallon oilcan and u can soon get the measure of whats needed . more thinners pressure ect

 

[pedrobedro]

Back of the shed door for me. My old gravity gun runs at about 40psi for cellulose and it's not hvlp compliant. I have Sealey Gold 1.8 and 1.4 which run about 2 bar which is not far off the other and the little touch up gun about 25psi on the dial but it's not that accurate and sometimes cut it down with the screw on the gun handle so no idea what to eventually.

 

[anjum]

Get a gauge which fits on the spray gun handle and measure with the trigger partly depressed (but not spraying paint).
Trial and error after that. It will depend on factors like type of paint, thinning etc.

 

[TriumphDave]

Thanks for the replies. My paint has arrived so I'll set everything up and maybe at the weekend mix a bit of paint and try to set the spray gun up. I have an old door I've primed ready to test on.

I have read set up guides where they say set the spray pattern/fan to 9 inches high, this seems a lot, or is that about right?

 

[Daz1968]

You set up the gun normally with fan fully open then set pressure to recommended settings and adjust fluid control to get correct shape and deposit of paint, then make minor adjustments as needed to get best results, that's how I did it, may not be best way but it worked for me, on my gun it was between 2 1/2 and 3 turns on fluid.

 

[Wendelspanswick]

The narrower the fan the more passes you have to make which is fine if you are learning but becomes boring if you are spraying a bonnet!