it feels rough to the touch not smooth as it should be imagine a sheet of sand paper and a sheet of glass feel the difference thats what sandpaper effect is
I haven't come across it yet. And hopefully I wont. Didnt even get it when i was re-spraying cars. Also thank you for your feed back.
on another note..
You think 15-20 psi is enough to run a airbrush. Seems to do the job. But when the trigger is down. I lose about 5psi . Should I invest into a real compressor?