over activated universal

mike r

mike r

Promoted Users
Its 2am, Im exhausted, I was mixing some universal to put coats 3 and 4 on some Silverado parts. I had roughly 4 oz of mixed universal left in the cup. Of coarse this is not enough, so I decided to mix up some more in the same cup. I add 12oz of Universal to the cup giving me 16oz. Not paying attention, I add 16oz of slow activator, and a cap full of retarder. Then spray my 3rd coat. let it sit for 30 mins, no issue. then I start my 4th coat. sprayed two doors no issue. When I got to the bumper cover and the fuel door. The third coat had cracked in a few places. I can fix the cracking but what had happened to make it crack and what if any are the lasting effects of over activating by 4oz?
Also I did not turn my small 12" exhaust fan off for the 30 mins between coats. the bumper cover and the fuel door were the closest to the fan. did that have anything to do with it.
 
i actually just had a conversation with a guy about this issue on monday. he told me it is because the clear has massively shrunk. not speaking of SPI specifically. we were talking about HOK.
 
just giving my educated guess.....with universal clear the cat isnt highly concentrated hence the 1:1 mix. i would say in the end its not going to matter and the clear film on the car will probably be just fine. if you did that with production, speed or euro clear it would be a different story. as you found out though it will change the cure rate and flash times. it throws that all out of whack. paint cracks like that when it gets into a sensitive stage. it will be partly cured and mostly flashed then you put your next coat on which is solvent rich. that 4th coat flashes and skins over too quick but the layer under is soaks up the solvent and swells up. coat 4 has a skin but the base moves and expands from the solvent making cracks. this is really common when spraying something that flashes fast over thick and fresh epoxy which is very slow to cure. your fan probably did not help the situation as it caused the clear to skin over and flash too fast. again, just an educated guess from using that clear for 20+ years now. 10% over catalyzed is typically acceptable. i have never done 30%. if barry or anyone from spi says something different then roll with that advise.
 
Here are a few photos.
 

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Maybe you can sand that clear flat as long as there’s enough there to get it out and spray a couple more coats on? Maybe let it sit a bit after it’s sanded and opened up in case any solvents are trapped?
 
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