Originally Posted by fordSR
In your original post, you mentioned the front of the car had bubbles and the rear didn't. You also mentioned "no wind" when you sprayed the rear. IMHO there is your answer. The wind caused the front to skim over trapping solvents and causing bubbles or solvent pops. I don't claim to be a pro but I do have a nice home-made spray booth with exhaust fan and front to rear air movement. I never turn on the fan until I'm done spraying the clear (each coat) and then only long enough to evacuate the booth, then the fan is off.
I use SPI clears and I cannot speak to the other brands of clears, but if I were using PPG, Dupont, or? I would use the same approach. In addition I always give myself a little extra flash time between coats, more is better than not enough.
Other posters have commented on other issues you may have and I cannot speak to those, but solvent pops can be difficuly to fix especially if you have many of them. If you applied three coats, the pops likely occured from solvent in the first coat so you may have a crator all the way to the first coat. Depending on how much film build you have in the clear, I would sand with a hard block and 1000 grit wet, roll it outside in the sun for 6 or 8 hours, then apply two more coats of clear.
Solvent pops are a pain in the ***
Jim, in my opinion you hit the nail on the head. The dead giveaway was the garage door being open with a breeze when painting the front, causing the solvent pops and no breeze when painting the rear of the car and minimal solvent popping there.
This is how solvents work in automotive paints. When you apply a solvent based catalyzed paint product the solvents need to evaporate. Before they evaporate the travel downwards until they hit hit metal. Paint is designed to work this way to give you "chemical adhesion". When the solvents hit the metal, they start to travel up and out of the paint, while this is happening, you have more air flow than what you need (because the door is open) and the catalyst or hardner is doing it's job by curing the clear but, the breeze is causing the clear to cure on top and not curing all the way through the layer of clear. The solvents are still going to come out, only now they need to break through the clear that is already starting to cure on top.
The same type of thing can happen if you don't have any air movement. Without air movement there is nothing to carry the evaporated solvents away from the painted surface and they just hang around there, not allowing the rest of the solvent to get out of the clear...and eventually causing the clear to pop.
There is a line between to much air movement and not enough, if that line is crossed in either direction, this is the problem that can occur.
Hope this helps.