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by Ron Joseph
March, 2006
Getting a High Quality Clear Coat (Clearcoat) Finish
with HVL Spray Guns
Q. I have painted for 35 years and have purchased 2 HVLP guns after all those
years of conventional guns (both DeVilbiss). My shop has been re-plumbed but
I cannot get a smooth finish with clear! I have tried cheap and high end clears.
Don't like to buff big cars and trucks unless I plan to. Any suggestions on
materials that I could obtain from you on this subject? I spray as a hobby now
and really like the concept of HVLP but just can't seem to tune them in right.
I spray mostly BC/CC and mostly overall jobs. Any help would be greatly appreciated.
A. Thank you for your email. I do not believe that the problem is die to the
clear coat!
There are many possible reasons why you cannot get the finish you are looking
for, but my guess is that you do not have sufficient compressed air going to
the spray gun. Your compressor must be able to supply approximately 50 psig
at the handle of the gun and 22-25 CFM. The conventional spray guns that you
have used for 35 years required 50-80 psig at the handle of the gun, but only
10-12 CFM. I suggest that you look in the compressor manual or on the name plate
to see how much CFM you are getting. With regard to the atomizing air pressure,
you can attach a pressure gauge to the handle of the gun. Depending on your
air cap and needle, you might not want to exceed 50 psig or you will loose to
much paint to overspray. Read the spray gun manual for the maximum pressure
at the handle.
If you are using a 1/4" air hose, then I strongly suggest that you change
it for a 3/8" air hose.
Soon we will be advertising a CD that teaches painters how to set up an HVLP
spray gun from scratch. As soon as the CD is available I will send you an email
to this effect.
Best wishes,
Ron Joseph
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