pits in universal clear

S

sellersrodshop

need a little advice.... when I shoot universal clear thru my "big" gun (sata 3000RP 1.4 tip) I get these small "pits" in the clear. they aren't like fisheyes, as there are no raised edges where the material has pulled from a contaminated spot. I don't have this problem with my small minijet gun when shooting bikes & never had the problem with my old sata 2000NR gun (also a 1.4 tip). I've tried playing with the air pressure & fluid adjustment some & doesn't seem to change anything. i'm getting tired of wetsanding, mixing up a capful of clear, touching up those spots with a brush & re-wetsanding before buffing. any ideas??

here are a couple pics, not the best but you can see there are a lot of them. really small, but very visible after buffing.



 
Air contamination? Any chance someone used a lube when assembling the gun? Doesn't look like solvent pop funnels but rather something that's getting put on the surface during the application.
 
I've disassembled the gun every time I've used it, which is only about 6-7 times over the last yr & cleaned it well, so would think anything would have been cleaned off by now.
 
When do you notice these?
1st coat? 2nd coat?
Give me an exact time frame if you can.
 
you really don't see them until the wetsanding process has begun since they are so small. on light colors they are hardly visible after buffing. did a hood on a silver blue mustang last week & maybe touched up a dozen that were visible. they really show on black though. i'm thinking it has to be something gun/adjustment related. I shot some small parts this afternoon with the minijet for the same car in the pics & they came out smooth as glass.
 
Have you taken the gun completely apart and soaked it? Might be some contaminate(s) in the air passages.
Looks like solvent pop to my eye . The "big" gun is letting you pour it on?
 
I was going to say and could be the beginning of solvent pop, espessally since you don't see them until you sand the clear.
However 9 times out of 10 when this happens it is not solvent pop (but could be) but mosture vapors in the line.

This could explain the small parts not doing it, so think back was the compresser cool at the time?
 
steve , i think you will find that it is a water droplet forming on the tip then exploding into the air stream. has happened to me many times . just has to be the right temp and humidity sometimes. small pieces dont take as long so less water build up. try doing some pieces with your sata and let us know what happens.
 
I agree with the above statements that it is line contamination, most likely water
 
I've had my air system fixed right for so long, I've started to forget about those kinds of problems. Investing in some kind of dryer for your air sure brings peace of mind.
 
come to think of it, I did have one of those mini water traps on my old guns for moisture that might form in the hose after the fact. also may try using another hose further down line that also has a regulator/separator on it. may cut down on any moisture that forms in the hard lines after that magic 50ft mark. i'll try a couple things & post up any changes... thanks!
 
moisture can form outside the gun. it can collect on the cap and then hit the air stream. the longer you spray the more that forms . dont think changing guns would effect moisture coming from the line . there are just days you cant paint unless you are in a really good controlled air space. imho those small ball filters restrict air too much and fill up fast anyway .
 
crystal cat litter dryer if you're on a budget, works fine.
 
I had that exact same problem on a couple of all overs. Usually scattered and random and mostly on horizontal surfaces. Not fish eye or solvent pop but tiny smooth indentions.
I changed the dessicant in my air dryer (DeVilbiss DAD-500) and have not had that problem since. The last two all overs, each had 5 coats of clear (2, sand flat, then 3), came
out smooth also, though they were done in cool, less humid weather.
 
ended up being a moisture problem. did some measuring of the lines & think that there wasn't enough line between the compressor & hose for the water to condense & hold in the trap & is condensing in the hose. moved to the next trap/hose in the system & have not had any further problems.
 
Bob Hollinshead;28221 said:
crystal cat litter dryer if you're on a budget, works fine.
Click to expand...
Bob, could you please explain? Is this slang for a dessicant dryer, or is this some home brew concoction?
With that said, is there a budget air dryer that someone recommends?
 
55 gal drum with a coil in it works well. but you need to have a drain in the bottom of the coil or it will just fill up with water. water in a barrel setting in the shade will stay cool. poor mans dryer .
 
Bob Hollinshead;28221 said:
crystal cat litter dryer if you're on a budget, works fine.
Click to expand...

I took your advice and made one of these a couple years ago, Bob. I have not had a single problem. All I have is a standard water trap after the compressor, the kitty litter contraption, and a motor guard toilet paper filter.

Mine is made out of fiberglass tube about 6 inches in diameter and 4' long. It is threaded for air fittings on both ends, with screens covering the holes to keep the litter in. I hung it on the wall with the inlet down and the outlet up, to keep the litter and moisture to the bottom.

I used fiberglass because my dad machines fiberglass for a living. Schedule 40 PVC would probably work. Although, I believe there is some controversy on the safety factor of using PVC for compressed air. I'll leave that up for debate.
 
shine;29279 said:
55 gal drum with a coil in it works well. but you need to have a drain in the bottom of the coil or it will just fill up with water. water in a barrel setting in the shade will stay cool. poor mans dryer .
Click to expand...

No kidding!! Never heard of this but it makes perfect sense. The copper would be the biggest cost.
 
i used 1/2 in pvc to make the coil . it is rated 160 psi . just put a t in the bottom and plumb out for a drain . coils easy and if it blows up it's contained so i dont need all the osha warnings. copper would be much better but cost more. did this to cool the air for my blasting hood for summer.
 
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