Ask the Expert Question-and-Answer Archive

by Ron Joseph

May, 2009

Spattering Clear Coat

Q. I'm having trouble spraying only the clear coat. The base coat sprayed fine and the primer it's ok but could be better.

I'm painting a 1992 5.0 Mustang at home. I have a car port in my backyard so I can seal it up as a paint booth.

My trouble with the clear coat is that it is coming out splattering. I tried a 1.7 mm instead of the 1.4mm ... same problem.

I'm using a U-Pol 4:1 clear. no reducer (doesnt state to add it).

What can be causing this? I purchased a 3 piece HVLP gravity guns set brand VAPER=$100

I have a craftman professional black 25 gal. 1.8 HP. scfm at 40 psi is 7.4 and 5.8 at 90 psi ... max 150 psi Oiled Pump.

A. Unfortunately I don't have the time to answer all your questions. However, it appears to me that your compressor doesn't have the capacity to put out more than 7.4 SCFM at 40 psi. You really need to put out more air volume (NOT air pressure). The HVLP spray gun usually requires approximately 12 SCFM. Keep the air hose as short as possible to preserve the pressure and avoid using any quick disconnects. I assume that a larger compressor would solve your problem. Remember, it's not only the psi that the compressor generates; it's the volume of air that will determine the quality of your paint finish.

Regards,

Ron Joseph