If you have never painted with a spray gun before, or if you have only recently converted over to spraying with modern high volume low pressure equipment, there are new things to learn. Here is a little primer Kevin Tetz did recently for us explaining which knob controls what function, and how to set your gun up before painting. The gun he uses in the demo is the Eastwood Concours HVLP paint spray gun (item #51550), but the controls are typical of most HVLP guns these days.
The first thing you should do after unpacking a new spray gun is to clear in thoroughly. The guns are packaged and shipped from the factory with protective oils and chemicals coating the insides of them so they can sit on a shelf in a warehouse for months without fear of corrosion. Run solvent through it like you would after painting with it. The Eastwood Aerosol Injected Cleaner (item #12846) is a spray can solvent complete with long thin nozzle specifically for clearing out tiny passages like those in spray guns.
This lower, larger knob on the back of the gun is the Fluid Control
The smaller knob above it is the Fan Control
And the knob on the bottom, which some guns don’t have, is the Air Control.
Now let’s put some paint in it and take it for a test spray. The first shot immediately tells us that the gun is not set up properly. The spray pattern is a concentrated spot of paint like a bull’s-eye.
The first thing to address is the fan control, opening it up for a larger size spray pattern. The best thing to do is turn it all the way out, then work in to fine tune it.
Now we get a fan pattern that is really wide, but splattered, and without a lot of paint in it.
So now we open up the fluid control knob all the way and really flow a lot of fluid through the nozzle
Now you get a nice, fat, wide, wet fan spray pattern with the correct football or elliptical shape. The tapered edges make it easy to lay down your overlap and get perfect coverage without tiger striping.
It may help to think of the spray gun like a carburetor and the adjustments like changing the jetting, throttle opening, float level/fuel pressure, etc. The goal is to get the right amount of paint and air coming out of the end of the gun, with the right atomization to flow out properly.
Another important consideration is air pressure. This gun requires 25-30psi at the inlet. That is important to know, because you have no way to measure it at the air cap. You can install a regulator at the end of the gun, but it may be awkward to paint with it there. The best thing to do is install the gauge at the gun, set the pressure at the far end of the hose to give you what you want at the gun, then remove the gauge to make the gun more maneuverable.
The air cap pressure is typically 1/2 what the inlet pressure is. And remember, the inlet pressure is properly measured with the trigger of the gun pulled in (and the fluid flow all the way closed).
And that should give you a good baseline to start spraying test panels with. Of course you want to practice on things that aren’t important before you attempt to paint your car. A good way to practice, without the need for elaborate safety gear, is to paint sheets of cardboard with water based craft paints that are non-toxic. This will allow you to tune you spray pattern, work on your overlap, and practice technique.