Thread: I'm about to give up . . .

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Yeah, I've grounded the parts, but I've done glass both grounded and ungrounded. Grounding a non-conductor never made a lot of sense to me, but I keep doing it.

I'm pretty sure I'm not getting enough atomization of the paint. I'm going to kick up the reducer a bit. I'm also going to get something to practice on before I do anything else. I guess I'll do some sanding on the parts I already have and see if I can get them to looking right.

This is how I've been tuning my gun:

Set the fan width as needed (you don't want to change it after you have "tuned" the gun). Turn out the material knob about 2 1/2 turns.

Set the air pressure at the inlet to the gun to the manufacturer's specs. On an HVLP gun, this spec is usually found on the gun, and is the maximum PSI it can have while still maintaining the maximum 10 lb at the cap for legal HVLP transfer efficiency (68 %). You are now ready to do a test sprayout.

Tape a piece of masking paper on the wall for the test. Hold the gun at a right angle to the wall, just as if you were going to paint the wall. Hold the gun at a spread out hands distance (about 8 inches, or 22 centimeters). Pull the trigger to completely open for a split second and then close it. You want an ON-OFF wide open-completely closed in ONE movement. You should have a cigar shaped pattern with complete coverage in the center with fading coverage going away from the full coverage cigar shape in the center. The center should be fully covered without any runs. If you have runs, either you are holding the trigger too long, you are too close, or the gun is simply applying too much material; in which case you need to screw in the material knob or turn the air pressure down. But most likely if you have turned the material knob out the 2 1?2 turns and the air is set at the factory specs, you are just too close or holding the trigger open too long.

The droplets you see trailing off the center are what you will use to "tune" your gun.

Turn in the material knob to make the droplets smaller (and or raise the air pressure). The balance you need to attain is the smallest droplet size possible before you lose the coverage desired. In other words, if you turn in the material knob too far, not enough material will be coming out to cover the panel!

Now, you'll notice that I said, "raise the pressure to the gun", while earlier I said to set it to manufacturers specs. We are talking a very small adjustment. It is a fine balance in material-to-air ratio and a little more air than specified is okay. Even if it is an HVLP gun the inlet pressure recommended is to maintain the 10 lb limit at the cap. Well, about three quarters of the country has no regulations for HVLP use, so if you go over the 10 lbs all it will do is atomize the material a little better. You may lose a little of the benefits of HVLP though. But remember you have a lot of control with the material adjustment knob.

After you are happy with the droplet size, DON'T TOUCH THE FAN CONTROL. It will change the PSI at the cap and will change the atomization you worked hard to get.

Do this sprayout every time you spray as material change, temp, and humidity will necessitate a sprayout droplet pattern test. Good luck!

I also found this interesting:

QUESTION: I have tried twice to paint a car with a primer, base and clear-coat system. the primer went on fine. the base coat went on a little rough like it was drying before it was hitting the surface. the first attempt at clear coat yielded too many runs. I started over from scratch, and again at the clear coat stage i first applied a tack coat then waited for 15 minutes for it to flash. I applied the clear-coat wet as possible it seemed to going on like it was splattering instead of a fine mist. I was using an HVLP gun with a 1.3 mil nozzle and about 13 psi at the gun. I have to redo it again as the car has 90% orange peel.

Answer: Crank the pressure up on that gun so that you have about 50 psi going into it. Higher if you want. the manufacturers give specs that meet environmental regulations for low over-spray, but aren't practical in real life.

Here's my take on the whole set of manufacturers' recommendations: The amount of thinner/reducer they recommend has more to do with keeping the Feds happy than it does with the quality of the paint job. I learned that when spraying the sealer. Kicked the reducer up about 25% and got a better job. I should have done the same thing with the base coat. Same thing on the pressure reccomendation for the HVLP gun. 10 PSI meets the Fed's rules. More probably does a better job. You can visit me at Leavenworth, but I'm going to get a decent paint job somehow.