Help with UV Clear Solvent Pop

1.2 on a mini jet is usually ok and more like a 1.4 on a full-size gun.
Iso clumping usually only happens on the first coat as when you spray the second coat it softens the first coat and the tin in the first coat will take some of the water but the problem can show up a week later or longer in form of what looks like a solvent pop or white color in clear.

Something has changed, could be heat and humidity or could be the compressor or could be watering the floor.
 
I don't water down the floor, so it's most likely the heat and humidity, both of which are high right now in socal.

Would adding retarder help?
 
It's a 50/50 gamble on the retarder, it has solved the problem in a couple of cases but others have not.
Worth a try might start with 5% retarder and see. Lots of factors here.
 
How bout if he tries 1 more test, pour some on can & see what happens. Spray some of it too elsewhere.
 
That can work on a flat surface but for my test to pinpoint the problem I wanted one coat.

On a flat surface, we have been in situations with a shops desiccant expired and had more coming but had to paint.
To get through this in one case a Honda hood, I had them spray two wet coats back to back with 0 flash and not bake.
Another was a deck lid on an older Mustang and I had the guy do all three coats non-stop.
It can work.

If this is done, once you stop you cannot do another coat same day or it will pop even if you wait for 10, 20,30 or 45 minutes.
You stop you are done.
 
That's not like any solvent pop I've ever seen. What I call solvent pop is teeny little bubbles all over, those are large and localized. Not that I have any idea why it's happening, but it sure seems like it's finding nucleation points, like carbonation needing something to grab onto to start, a contaminant of some kind, or tiny droplets of water.
 
Barry is spot on! When I was doing testing earlier and out of frustraion, when I started seeing bubbles forming about 2 minutes in, I hacked on a really wet second coat, and the bubbles went away. Waiting for the retarder to come in to see if it helps, will post the results.
 
I'm out of ideas! I've just about tried everything, and I still cannot get rid of the pop. Here are the things I have tried:

1. Added a desiccant dryer, aftercooler and refrigerated air dryer
2. 5%, 10%, 15% retarder
3. 5%, 10%, 15% less activator
4. All combinations of #2 and #3
5. Spraying back to back wet coats kinda works, but with darker colors like black, I can still see some of the bubbles and craters. With this method though, there is noticeable orange peel.

Strange thing is if I spray the coat light, it pops all over. The wetter I spray it, the less pop there is. Then no matter how light or heavy I spray on the 2nd or 3rd coats, I can't get it to pop.

Any ideas to help me?
 
I don't have anything, except to say that what solved a similar problem at my shop was a refrigerated dryer about 25' from the compressor, then a longer run around the building to the booth with the desiccant dryer right at the paint booth hose. The cool thing about the DeVilbiss/CamAir CT30 that we have is the desiccant bag also acts as a filter.

I think you might have some lingering issues with your air, like there is some residual water in a line somewhere that is still getting out. That's why I mention the positioning of the desiccant dryer. I personally think it's best to have it right at the spray gun air hose, and the hose should be replaced periodically.

Other than that, I got nothin'. It's a tough problem, for sure.
 
might be way off but have you checked your gun for any leaks or slight clogs, that close-up looks like trapped air almost like your gun is foaming the clear as it comes out. I would also look in the cup during the first trigger pull of clear and see if there is any foaming in the cup.
 
DATEC said:
might be way off but have you checked your gun for any leaks or slight clogs, that close-up looks like trapped air almost like your gun is foaming the clear as it comes out. I would also look in the cup during the first trigger pull of clear and see if there is any foaming in the cup.
Click to expand...

I'll take a look, but I've tried with 3 guns and they all produce the same result.
 
Remember Black, Dark Blue, and Dark green are twice as slow to dry as any other colors, so if those are the main problem colors, give more flash time between coats of base and between the base and first clear coat.
Also, a dry first coat can cause solvent pop with my clears, figured that out by accident 4-5 years ago.
Make sure you have proper SCFM so air at wall should be a minimum of 125, this shows its ugly face with high solids clears that don't have thickeners in them.
 
I think the problem your having is air is leaking into the gun creating air entrapment. I had same problem it just started happening outta nowhere. First I thought it was dirt, then solvent pop. It would happen right away on the first coat.

One thing I did was when it happened I would actually pull the spray gun so air would come out and point directly at the craters. Then have every so slight amount of clear come out. You could actually pop the bubbles out and add clear.

I switched guns and I also used a new 3M cup. The problem went away. I saw clear in my gun near the 3m adapter and it was bubbled like a bubble bath.

The problem not only happened in clear but it started happening when I sprayed waterborne primer. It would cure with pinholes.

Basecoat etc no issues.
 
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Also forgot to mention. You said you changed guns but did you use the same needle/nozzle set? The same happened to me.

What I did to fix was teflon tape the 3M adapter, the nozzle threads and the aircap threads.

Solved all my issues. Takes extra few minutes setup time to teflon everything, but saves the headache. Try it, nothing to loose.
 
I don't think there is air leaking into the gun as there are no bubbles in the clear. All 3 guns I tried have their own tip/nozzles, but they are all mini guns with a 1.2mm tip, a sata minijet 4400b, a devilbiss gti pro lite, and an iwata lph-80. I don't see the bubbles on the clear as I am spraying, the bubbles only manifest after about 5 minutes.

I'm going to try with a devilbiss gpi with a 1.4 tip. Been reluctant to do so as I use that as a primer gun and I like having dedicated guns for each stage of paint.
 
It def not solvent pop. Its air entrapment...

Get your gun further away from the painting surface and up the pressure. Maybe go down in nozzle size?
 
Danny23 said:
Did you ever figure out the problem
Click to expand...

Nope, I've replaced everything that can be replaced, and even tried out of a 1.4 tip on full size gun, and it's still showing up.

From my compressor, it's 30 ft of copper line with drops, to a refrigerated air dryer, then 10 feet of copper to a devilbiss QC3 out to a 10 foot rubber hose to a wall filter/regulator, and finally 10 more feet of rubber hose to my gun.

I have no water coming out past the second drop, so I've ruled out water in the air as I doubt water vapor will make it past the RAF and QC3.

I've tried all manners of gun tip sizes, air pressures, and spray distances with 4 different guns and nothing has changed. I've tried on all types of surfaces, plastic, metal, painted, unpainted, solvent based, waterbased, wax and grease remover, not wax and grease remover, cleaned, not cleaned, dawn soap, etc...

Could it be contamination of some sort in my booth? The problem never shows up right away as I'm spraying, only about 5 minutes after I finish spraying. On a side note, I can spray another brands' matte clear without a problem, comes out silky smooth.

I'm out of ideas, I'm residing to spraying 1 wet coat, let it pop, bake, wetsand, then spraying a second wet coat. Before this all started, it was 2 heavy wet coats and done. I could literally run it to hell on both coats and there wouldn't be any solvent pop, it was great!
 
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