I am completely new to spray painting. I just finished my first experiment spray painting with an HVLP gun and a compressor. I am spraying a General Finish high gloss Poly, tinted black. My test cabinets are MDF.
I had several problems, but I think I should focus on two basic principles, controlling my air pressure, and controlling the thickness of my finish.
How does one set the air pressure for a spray gun? I did it this way: I set my air compressor at 60 PSI. I closed my control flow valve and fan valve, and pressed the air gun trigger. The needle on the control gauge at the base of the gun dropped. I adjusted the knob until the air pressure was about 29 PSI, the recommended pressure. Without the trigger on the gun pressed, the air regulator shows a much higher pressure than 29 PSI.
Getting the thickness of the finish correct really proved difficult. The thickness is supposed to be between 2 and 5 Millimeters. I sprayed a thick piece of paper on a horizontal surface as a test and used my wet mil gauge. It seemed I couldn't get a thin enough finish. Every time I used the wet mil gauge, it showed a thickness well above 5 mm.
Finally, I got a thinner coat by moving the gun pretty fast across my work. This technique produced a finish seemingly to thin. None of my experiments produced a nice glassy surface, but I also didn't prep my wood correctly. I used a shellac with wax as my sealer, and yes, the first coat just slid off. (Luckily these are just practice carcasses. Lesson learned.) I sanded the carcass and applied two more coats, but my finish seemed more flat than glossy, and it seemed to show the sanding beneath.
I am not sure on the size of my nozzle. I ordered my gun from Jeff Jewit (and I have his book as well). The gun comes with an additional nozzle of 1.5 mm and 2.5 mm. I am not sure of the nozzle on my gun.