Contamination or solvent pop?

serjik911

serjik911

Promoted Users
Hello everyone.

car #1.
sealed, and put base coat, white color. Temp 70, side draft spray booth. let it sit overnight. Came back in a morning, everything look great. Sprayed 2 coats of spi universal medium, 30 mins between coats. looks great. after 15 mins turned off fan, everything looks good. In few hours started to see some contamination or solvent pop. And after a day drying took a picture. Contamination/pop is on each panel, horizontal or vertical. and on right side of the hood its a lil bit more, than everywhere else. Checked the thickness and in average have 2 mils of clear everywhere.

car #2.
sealed, base coat, let it sit overnight. everything looks great. in a morning cleared with different faster clear, by tds has 3 mins flash between coats, which i did. 2 full wet coats. after 15 mins turned fan off. in 2 hours the clear was good to touch, and i see less but same pop/contamination as on first car. And this time, if i look very close and straight to it, it even has some grey color in it.

The shop is located next to demolition and construction waste recycle, and when plant works, everything around 3 miles is in dust, like on photo. Its like nuclear winter, honestly.

when i turn on the booth, i dont see noticeable dust, but yesterday i turned off booth lights and and turned on just a flashlight, and saw a lot of micro dust coming thru filters.


So, I am pretty sure that it is contamination, but, the only thing i dont get is why dont i see it right away as i spray clear coat, and only after it starts drying up to the next day?Why it looks worse on a good slow clear coats and better on cheap fast clears? It also affects clear coat depth. Is it contamination or its a solvent pop?

Thank you
 

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I can't really tell anything from the pictures but from your description I think it's solvent pop. At least with the first car using Universal. Probably with the second as well. Couple of things. You were using medium activator and left the fan on for 15 minutes after the last coat. SPI does say to turn off the fan as soon as you finish your last coat. And medium activator in a booth with airflow will cause the clear to skin over too quickly. Not turning the fan off within a minute or so after clearing also will cause it to skin too quickly, trapping solvents, leading to solvent pop.

If it was contamination it would show as you are spraying. It would not do that if contamination entered the booth after you had sprayed. You might get some trash on the surface but to get fisheyes from contamination, it always shows as it's being sprayed.

A good guide to when a clear has flashed enough is to test with your gloved finger on a piece of tape or masking on the car. When you can drag your finger on the tape/masking and the clear doesn't string or stick to your finger, it's flashed off enough. I always use that method when doing collision/production rather than go by what the TDS says.

With the Universal, use slow activator and turn the fan off within a minute or two of your last coat. If you have adjustability in your booth, cut your fan down some as well. Just enough to evac the overspray. Second clear same advice. At least cut the booth fan down and turn it off within a couple of minutes after your last coat. Don't wait 15 minutes.

Air pressure can also be a cause of solvent pop but I'd say it was more doubtful in this situation.
 
Chris_Hamilton said:
I can't really tell anything from the pictures but from your description I think it's solvent pop. At least with the first car using Universal. Probably with the second as well. Couple of things. You were using medium activator and left the fan on for 15 minutes after the last coat. SPI does say to turn off the fan as soon as you finish your last coat. And medium activator in a booth with airflow will cause the clear to skin over too quickly. Not turning the fan off within a minute or so after clearing also will cause it to skin too quickly, trapping solvents, leading to solvent pop.

If it was contamination it would show as you are spraying. It would not do that if contamination entered the booth after you had sprayed. You might get some trash on the surface but to get fisheyes from contamination, it always shows as it's being sprayed.

A good guide to when a clear has flashed enough is to test with your gloved finger on a piece of tape or masking on the car. When you can drag your finger on the tape/masking and the clear doesn't string or stick to your finger, it's flashed off enough. I always use that method when doing collision/production rather than go by what the TDS says.

With the Universal, use slow activator and turn the fan off within a minute or two of your last coat. If you have adjustability in your booth, cut your fan down some as well. Just enough to evac the overspray. Second clear same advice. At least cut the booth fan down and turn it off within a couple of minutes after your last coat. Don't wait 15 minutes.

Air pressure can also be a cause of solvent pop but I'd say it was more doubtful in this situation.
Click to expand...
Should I turn off the fan right away with euro2020 ? Or only universal?
 
serjik911 said:
Thank you, Chris, for helping. Another question, do you suggest slow reducer at all steps, like sealer and base, to prevent solvent pop?
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That's what I do. You are in a booth so you have airflow. If you have to spray in cool temps like 65- 68 or so then you could blend the slow and medium, 1:1 or thereabouts. But having the airflow of the booth helps speed up the slow so if it's 72-73 up it works great. You may want to keep blending to suit your taste and how much work you have. But medium in 75 degrees and up in a booth can lead to problems like you had.
If you can adjust the fan in your booth, turning it down to where it is just enough to evac the overspray helps a lot as well. And it cuts down on the trash the booth sucks in.
 
Last guy I worked for, when I came there they had the booth fan running wide open. They were having a lot of trash and other issues because of it. I put a VFD (variable frequency drive) on the 3 phase fan and then we were able to adjust the fan down. VFD worked great. I ended up spraying at around 37-38% versus the 100% that they were spraying at when I got there. Fan was sucking so much you couldn't open the man door without really pulling.:) After I put the VFD on and cut the fan down, I could do nearly dust free jobs in that old booth. Never had to buff collision/production stuff.
 
Chris_Hamilton said:
Last guy I worked for, when I came there they had the booth fan running wide open. They were having a lot of trash and other issues because of it. I put a VFD (variable frequency drive) on the 3 phase fan and then we were able to adjust the fan down. VFD worked great. I ended up spraying at around 37-38% versus the 100% that they were spraying at when I got there. Fan was sucking so much you couldn't open the man door without really pulling.:) After I put the VFD on and cut the fan down, I could do nearly dust free jobs in that old booth. Never had to buff collision/production stuff.
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I saw that intake fan has shutters system full open, gonna adjust it tomorrow. It will create negative pressure, but at this point I don't care, I didn't have a single fish eye from shop air
 
Chris, do you use the same thought process for any sized part ( mirror, bumper...). Seems that the paint doesn't know what you are painting so, in this case, size doesn't matter.
 
If so then yes I pretty much used slow only when I was using a booth. LIke you said the paint doesn't care that what you are painting is small.
 
AAE said:
Yes. Following your logic.
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Not saying other ways won't work, just how I do it. In my mind if you are having issues with pop using medium reducer/activator it will happen on something small just as easily as it would on something large. Plus him being in a booth changes things versus a non booth, low airflow environment.
 
serjik911 said:
Did you mean too high air pressure or too low air pressure? Please, explain a bit more
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Too low. With a high solids clear, too low can cause the solids to "clump" and trap solvents. Not the greatest description. Maybe Barry or one of the other guys can describe it better. I've never had the issue myself. But I never spray clear at a low pressure either.

As for what pressure is low? That would depend on the gun. The low side recommendations of gun manufacturers are where it would start to come into play. As long as you are spraying with a pretty decent amount of PSI it's not an issue.
 
Chris_Hamilton said:
Too low. With a high solids clear, too low can cause the solids to "clump" and trap solvents. Not the greatest description. Maybe Barry or one of the other guys can describe it better. I've never had the issue myself. But I never spray clear at a low pressure either.

As for what pressure is low? That would depend on the gun. The low side recommendations of gun manufacturers are where it would start to come into play. As long as you are spraying with a pretty decent amount of PSI it's not an issue.
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Will the same work with cfm?
At current place I have a 3/8 line from compressor thru the whole shop thru 5 filters on the way to spray booth. My both SATA hvlp 5000 and 5500 can't brake paint if it is not over reduced and spits lie crazy. I'm pretty sure cfm is terrible at the gun
 
I wonder the same thing about CFM in y system. All 1/2" copper pipe but through a HF refrigerator dryer, 2 filters, 10lbs desiccant, 2 more filters, a regulator then 1 more filter ahead of 38' of 3/8" air hose, and finally the diaphragm regulator on the guns. whew!
 
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serjik911 said:
Will the same work with cfm?
At current place I have a 3/8 line from compressor thru the whole shop thru 5 filters on the way to spray booth. My both SATA hvlp 5000 and 5500 can't brake paint if it is not over reduced and spits lie crazy. I'm pretty sure cfm is terrible at the gun
Click to expand...
Yes that's definitely a problem. Unreal that you are able to do anything with 3/8" line. No real work around either. Tell your Boss you need bigger air lines. With the guns we use today volume is as important as pressure. With that tiny line you don't really have either. Only real solution is bigger piping. 3/4" would be considered the absolute minimum. The longer the amount of piping the bigger the pipe needed to maintain pressure.
 
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