crack/shrink in universal clear

L

LSUfj

Its been a few weeks, but I'll try to recall all of the steps that led up to this. I want to know where I screwed up so that it doesn't happen again. I am repainting an FJ40 that I previously had major cracking/shrinking from my first paint job. The first go round, I'll admit I was overwhelmed and rushed and the results showed. I think the previous issue was applying too much 2k, too fast. After it was all cleared, the cracks showed up just about everywhere. I sanded everything off where these issues showed up and sanded the rest with 180. I then started over using "the perfect paint job" as my guide. Here are the products I used this time around:

- SPI epoxy primer, evercoat rage gold, SPI 2k regular, dolphin glaze (very minimal use), reduced epoxy sealer, Omni DBC base, SPI universal clear

Schedule was something like this:
Thursday - 2 coats epoxy
Friday - filler/sanding
Saturday - 2 coats 2k (30mins flash)/block , spot epoxy
Sunday/Monday- no work
Tuesday - a little more filler in a couple spots, 2 coats unreduced epoxy (30 mins flash)
Wednesday - wet sand epoxy with 600
Thursday - minor sanding/masking
Friday - 1:1:1 sealer (wait 1.5 hours)/ 3 coats base (45mins flash) (advantage refinishing slow reducer)
Saturday - 3 coats spi UC with slow activator (temperature around 90F). Flash time was 30 mins from wet to wet. I didnt wait 30 mins after each coat, including about 10-15 mins of spray time.

about two days later I rolled it out in the sun, around 90F out

The issue is some cracks/shrinking in a few spots. I cant correlate this with any particular underlying body work. The only thing that comes to mind is there may have been spots where the epoxy went on too thick and became mottled. These areas were sanded flat on wednesday. A couple thoughts on what might have contributed: should have waited a bit longer between clear coats, not enough cure time for epoxy, put in the sun too soon, previous finish rearing its ugly head again?

I wet sanded and buffed one section and the cracks were significantly reduced, almost gone. Seems like its in the clear since everything was straight up until about a week or so afterwards. Anyway, here is a pic of one area with the crack showing in the light reflection. A similar process was used for all of the other panels with no issue. Side note/quesetion-is the surface condition showing dieback?
fj40 paint.jpg
 
The clear cannot crack if mixed right but will magnify. The only way to know what caused it is to carefully sand and see where crack ended.
It something down deep as that looks pretty nasty.
 
I'll try to do that this weekend. If its something on a layer below the clear - is there a way to identify the problem prior to applying clear? Everything seemed perfect prior to applying the base/clear.
 
From your original post, it seems that you did not sand all the cracking finish off, therefore that new crack will be in an area where you did not sand back down to metal; in other words, it is your original mistake come back to haunt you.

If freshly applied material is cracking in one area, it's likely waiting to crack in another.
 
Pretty sure you guys are right, although there was very little material left, just a few low spots that I am pretty sure are not where this is showing up.The only products that were the same in both cases were the filler and the base. I'm thinking, or hoping, that this is occurring where the base went on too heavy. Im planning to sand these two spots with 600 dry in hopes of slowly revealing the issue. Any suggestions on this method?
 
Looks like body filler cracking. Never heard of or seen basecoat cracking. You'd have to put it on with a paintbrush to get it to crack like that. Only sure way to fix it is to grind it out. As you are grinding it out pay attention to what it looks like underneath. You should grind it out much farther than just the local crack. Take it down to metal 2 to 3 inches around the crack.
 
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