Contamination or solvent pop?

Problem the OP has is that he has to use 1/2 lines from the compressor to point of use which results in massive pressure drop and little volume. That is what is causing his issues. There isn't a lot he can do short of convincing the Owner to redo the lines.
 
SPI epoxy mixed 1:1:1 is ready to recoat over in 15-20 minutes. I like to give it a little longer and it's not really sealing anything. More of an adhesion promoter. If you are working in a production/collision environment then urethane sealer is a better choice IMO.
 
I personally think the 3rd coat of clear might be part of the problem in this particular spray environment. If, as I think I read, the jobs get 3000 and minimal polishing, 3 coats is massive overkill. Also you can skip the sealer in a collision shop environment as long as the primer was urethane and not epoxy. The less material you put on there, the less it's going to have solvent trapping problems.
 
serjik911 said:
Could I over atomize clear. What signs of that would be
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I don't know what the effects if any would be of that. Never heard of it. I feel pretty sure the issue is the air lines. Low air pressure and under-atomization. As best I understand it, with a higher solid clear, if you don't have enough air pressure and volume, you aren't "breaking up" the clear well enough and it traps solvents. I'm probably not describing it correctly but that is my understanding of the issue. Over the years there have been multiple threads here with guys having this issue and usually upping the air pressure solves it.

With the air lines you have and the pressure drop you described IDK what can be done to fix it. The only thing I can come up with is to over reduce your clear. That would have the effect of dropping the amount of solids and make it less likely to pop. Keep in mind that when you over reduce your mils per coat are less. Turning off the booth between coats and immediately after your last coat (soon as the overspray evaps) would help too I think. Best thing you could do is run some proper lines to your booth.
 
So, in the case of this Audi. Primer was drying for a week, base was drying overnight. The only reason I see for solvent pop is solvents from 1st and 2nd clear coat didn't come out, right?
So, over reducing the first coat, let it sit for half hour, and spray normal 4:1:1 finish coat should make a trick, am I right?
 
With slow reducer the only time I have had pop problem with UC was when I layed it on way to heavy in a few spots. Like Chris said I typically have the pressure cranked up for anything SPI. typically in the low 30 PSI range.
 
JimKueneman said:
With slow reducer the only time I have had pop problem with UC was when I layed it on way to heavy in a few spots. Like Chris said I typically have the pressure cranked up for anything SPI. typically in the low 30 PSI range.
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OT but interesting to me at least, when I cranked up the pressure using my Sata RP, an extra 8-10 psi over what I had been spraying Universal with it made a huge difference. I had always been able to spray UV OKish, but not as nice as other clears. With the extra air pressure the stuff sprayed so easy and laid out like glass. Just amazing what the extra PSI did.
 
Wow is this clear really that temperamental? I’ve always just stuck to medium activator and medium reducer. But I do understand everyone’s environment and spraying style is different. But I thought one of the good things about euro was its “flexibility,” as in being able to control it with different speed reducers depending on the job, over reduce to save on material for budget work, etc. Sounds kinda dangerous now to be experimenting with different speeds, ratios, etc haha.
 
Whitesnake said:
Wow is this clear really that temperamental? I’ve always just stuck to medium activator and medium reducer. But I do understand everyone’s environment and spraying style is different. But I thought one of the good things about euro was its “flexibility,” as in being able to control it with different speed reducers depending on the job, over reduce to save on material for budget work, etc. Sounds kinda dangerous now to be experimenting with different speeds, ratios, etc haha.
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Not really. The main issue for the OP is the 3/8"(!) air lines from the compressor to the point of use in the paint booth. He mentioned the issues he was having with pressure drop etc. Amazing that he can even paint at all with that setup.

In the booth medium is really too fast as if you have airflow it just works with the medium to flash off faster leading to trapping solvents.
 
There are environmental factors that can add up to problems, imo. Inadequate compressed air, perhaps it is not dry air, excessive booth air flow, lots of things can add up to problems that don't indicate a problem with the clear per se.
 
Chris_Hamilton said:
Not really. The main issue for the OP is the 3/8"(!) air lines from the compressor to the point of use in the paint booth. He mentioned the issues he was having with pressure drop etc. Amazing that he can even paint at all with that setup.

In the booth medium is really too fast as if you have airflow it just works with the medium to flash off faster leading to trapping solvents.
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Yeah that’s for sure. Spraying HS clear with 3/8 lines sounds like an uphill battle. I guess one part of euro I’ve never fully got, was if I use one speed activator am I suppose to use at least that speed reducer and slower? Faster? Or can you mix and match different ways with positive results?
 
crashtech said:
There are environmental factors that can add up to problems, imo. Inadequate compressed air, perhaps it is not dry air, excessive booth air flow, lots of things can add up to problems that don't indicate a problem with the clear per se.
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Yeah I spray in more of a home built setup with an exhaust fan so I certainly don’t get the airflow you pros get in a booth. So I suppose in some ways that can help at times.
 
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