This is what I posted on autobodystore.com board. Two replys suggested ways to set the air pressure correctly, but I already did that, so I'm still searching for an answer that'll make the light bulb blink on over my head.
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My first attempt to use an HVLP (Finishline), painting Glasurit 2K Urethane primer. Pressure is good, spray pattern is good, finish and application is good. Problem: I'm using almost more paint than I would with a normal gun. I kinda thought HVLP would let me squeeze a little more cover out of my $$$ paint.

The directions that came with the gun are pretty limited, so I'm asking what I'm missing here? I am getting a _lot_ of dusting; the whole garage is covered with paint. I'm looking at the other adjustment knob on the gun - not the spray pattern, but the air volume. Could that be adjusted too high?

BTW: Maybe my supplier underestimated how much primer I'd need: I had a gallon (1 1/2 gallons when mixed 4:1:1). I sprayed 2 coats on: inside and outside a full sized pickup cab, hood, front fenders, inner skirts, grille and radiater support (or, the whole truck, minus doors and bed). Does that sound right?

I also found out the hard way _not_ to use the internal filter (the one between the cup and gun) when spraying primer; it clogged up when I had almost a full cup and had to trash the whole thing.

TIA,

Do you have a pressure regulator with a gauge on the gun itself? I run 30-40 psi at the gun. Also, there are two knobs at the back of the gun. The top one is for spray pattern, and the bottom one is for the volume of paint output. You may need to back that one out some if you're getting alot of dusting, or your spray pattern may be too wide.

Randy,

Yup, the gun came with a tiny gauge and regulator. With the trigger partially squeezed, just spraying air, I'm showing 23psi at the input to the gun, as recommended, which they say gives 10 at the tip. My wall gauge is running about 60-65psi.

I kinda thought it would be the volume. That's _paint_ volume, huh? That makes sense. I'll be playing with that one tomorrow.

I did test shots on a trash hood and I got a single straight line about 1" wide and 12" top to bottom (for about a 1 second trigger squeeze). None of the curved or dumbell patterns like in the directions.

Pattern sounds right on, probably the volume control needs adjusting. Let me know how it turns out. :cool:

I backed the volume knob way off. Pulled the trigger and started turning the knob in until I felt the trigger starting to move. Then I turned the knob 1 & 1/2 turns further.
That's probably not even close to being correct for a good painter, but it works for me.

Paul, I run mine wide open. I don't get any orange peel, runs,...... Just depends on what your comfortable with I guess.

Randy - 30-40 lbs. at the gun on a Finishline? The directions make it sound like the world will come to an end or something if you go over 23.
Do you ever change the tip size?

If you are having a "dusting" problem try grounding the metal you are spraying with a jumper cable to a water pipe.

Sometime when you sand a lot on somethig, it creates static electricity that repels the material you are spraying, the result-dusty overspray everywhere. Grounding helps to neutralize the static charge so your material goes where you want it to.

I've done this for years, its always helps. Also I try to wet sand everthing I prep, seems to help also,

About volume, HVLP guns need good air volume. Make sure your hoses AND connectors are large enough (diameter) to carry a sustained air volume for the duration of your spray time.

One more thing, Have your supplier shake the snot out of your primer and color, even high build primer needs the solids suspended well to be used efficiently.

Hey, nosto -
Went through a gallon of primer so far on just the doors (inside and out) the outside of the bed, and the fenders and hood. Haven't done the cowl, tailgate or cab yet.
Part of it is that I don't really know what I'm doing - plus I sanded a lot off block sanding. That's some expensive dust on the floor. Think it's going to be fairly straight, though. -- I hope.:)