Does this make sense?

B

Brad J.

Oldtimer
I was shootin the crap with the local jobber that I have known a long time. He's knowledgable and sprays himself. Anyway, I was telling him that when I spray clear on a resto I spray 1 coat in the morning, 1 at noon, 1 afternoon, and one at night before I quit. He told me that I was asking for solvent pop doing that. I asked him to explain but he really couldn't. It was like asking a UAW retiree to explain his reasoning. Just cuz I guess. I told him it made sense to me that letting a lot of time between coats allows the gases to escape. He said 20 min between coats is best and then the entire 3-4 coats will cure together and are less likely to trap solvents. It seems to me that way you have 3-4 barriers to stop the gasing? Or doesn't it matter at all. I've had solvent pop once and I think it traced back to my radiant floor heat in the booth set at 90 degrees. Surface temp was over 100 degrees as the floor temp was also that warm to heat the air to 90. I think that hot of surface temp skimmed over the clear and about 3 months later it popped. That or it was just bad luck as I painted two other cars the same way and they never did it. All three were painted with dupont premier clear before I switched to SPI.
 
only time i can get any spi clear to pop is when i accelerate it and bake it too hot too fast. i don't know brad, seem to me your thinking is right. i don't see any problem with what you are doing. i think your flash time are a bit excessive though but i don't think it will hurt anything. with flash times even as long as yours the clear is not cured out and the next layer will still bite into it just fine.
 
i think most high-end clears can be recoated with itself within 12 hours? not sure what the spi window is but i assume it is the same or even longer. Doesn't seem to make sense saying that would cause solvent pop. You are definately NOT trapping solvents by waiting that long between coats.

Only time i've gotten spi to pop was either recoating too quickly in a cut/re-clear scenario or rushing the flash times...........hey it happens! lol. will happen to any other clear done the same way also.

I remember years ago when sikkens came out with their new "xp" hardener for their AutoClearIII. Main sale was the less chance of solvent popping while hammering the coats on, as their "standard" hardener was more prone to it. quicker flash times also. Sounds like a gimmick but there was a considerable amount of difference. XP is the most used hardener now.
 
so to this guy then, doing 'the perfect paint job' on the SPI home page would also cause solvent-pop. Seems to me I've heard this 'just cuz' routine a lot and I don't much like it.
 
Well, I always show a respect for the guy as he has an eye for hand color matching colors on the old cars I work on. He's good and I need him for my type of work so I'll never confront him to hard. Remember it is a Dupont jobber so they still push vari-prime for bare metal instead of epoxy so I don't pay real close attention when they talk paint. This guy used to own the place and then sold out to a larger company and he is now the outside sales guy and old car color guy so he's been around for decades. It just didn't make sense how solvent pop could happen under these circumstances.
 
Another thing that really helps to stop solvent pop is to give the basecoat a good time to purge it's solvents before shooting your clear. The 20 minute rule for production work just isn't long enough IMO. Use slow solvents-the slowest you can get by with so each coat stays open the longest amount of time to evap solvents. I've never waited hours between coats of clear but it does sound like a good way to do it and I bet you end up with less chance of runs, lightly tack rag between coats LOL?
 
i push flash time to the max on everything but clear. with uv i hammer a coat then come right back on it .
 
in the summer heat doing an all over (old cars), i see no difference in waiting 20-30 minutes over just going to my next coat right after my first. Very Slow activator. I run reducer through the gun after every coat and mix my next batch of clear. By the time i'm back in the booth its ready to go.

In the winter, even though heat in the booth, it just isn't like the summer heat. I give it the 30 min rule.
 
I tend to wait the same summer or winter...by the time I get around a car, run reducer thru the gun like Jeremy does and mix my next coats amount, I start again.. Usually 20 minutes or so.. Sometimes longer, sometimes shorter..
 
We discussed this on the phone yesterday and there is no problem doing the three coats the way it is being done, although their is a slight potential of a problem if one day the humidity and temp are just perfect but that would be 1 in 100 odds.
In a perfect world 30-60 minutes would be extreme overkill and may be safer, their is a window of 60-80 minutes where here again if conditions are perfect you could hit a sensitivity period but again 1 in a 1000 odds. (instead of 1 in a 100)

ALSO, Mr Dupont was right what he said about his clears but we are comparing apples and prunes, so does not apply to the SPI.
 
Barryk;5453 said:
ALSO, Mr Dupont was right what he said about his clears but we are comparing apples and prunes, so does not apply to the SPI.
Click to expand...


I don't think I'll be buying overpriced prunes any time soon lol

Excuse my useless reply to this interesting thread,I just couldn't resist.
 
Ouch, Andy!
That jobber had called me early this week after seeing this post on here. That is why I called Barry to discuss the differences in clear. The jobber left a message wanting me to call back if I had any questions or didn't understand what he was saying. (pretty damn cool). I think it was somewhat of a communication issue. I always want a concrete reason why the sky is blue. What he told me is the Dupont clears are designed to be recoated within 20 min. Say between 20-45 min there is a greater window of potential pop outside the 20 min window and that is the way it's designed. I was fishing for a concrete reason that I never really got so I just figured "just cuz" was the answer. He was trying to relate that it's just the way it was designed and end of story. He did ask why I would wait so long and that he's never heard of any shop doing. (after talking with Barry I guess I'll change that rule to an hour. I implemented that rule when I spray epoxy and just carried it over to clear to be safe.) Todd also sent this question out to dupont and the long wait times could lead to layed paint that could potentially show up in the cut/buff. Barry assured me the SPI is good for 24 hours before that can be a problem. Thanks for the feedback and in the future I won't try to compare apples to apples when there isn't a comparison.
 
Brad, I saw your post earlier in the week and when you desribed the jobber in question , I immediately knew who you were talking about. I hope there's no problem of me mentioning your post to Todd. I'm alot like you for always wanting to know why or how come something works or doesn't. I've known Todd for over 15 years and haven't met many people that are as willing to help out in the bodyshop than him. The guy is phenomenal at tinting color,and always seems to come through with those old car colors that nobody wants to deal with. Glad to hear you touched base with Barry on this subject and you have answers to your question. Joe
 
Barryk;5453 said:
again if conditions are perfect you could hit a sensitivity period but again 1 in a 1000 odds. (instead of 1 in a 100)

ALSO, Mr Dupont was right what he said about his clears but we are comparing apples and prunes, so does not apply to the SPI.
Click to expand...

Years ago I seen the old DuPont 7500 and 7600 clears wrinkle up during this sensitivity period-when the second coat of clear was shot and the first coat wrinkled, only seen it happen a few times.
 
all this talk of Dupont is making me have nightmares of my first project long ago........
 
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