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High Life 08-19-2017 12:47 PM

U-POL Gravitex issue
I just finish spraying a coat of U-pol Gravitex Black over my rust repair and I am seeing this:

Little white lines or cracks in the Black coating. However not consistent - only in a few areas with no real logic to areas affected. If you run your finger over it - it will not chip or anything - its almost like it expanded too quickly for the pigment to cover..

Schutz gun was used at 65psi
Coating was shaken and mixed thoroughly
Coating went over a self etching primer laid down 3 hours before
Primer was sanded with 400 grit and wiped with rag with real light coat of wax remover (never wet).

I'm guessing its not a huge problem as I plan to paint over with guards red.

Not sure what to think - guessing a reaction to primer?

Should I worry - or just wait till dry and move on?

High Life 08-19-2017 01:15 PM

Upon closer inspection - now that it has setup and dry to the touch - the "white cracks" is the primer showing through.. Looks like there is a chemical issue with the etching primer I used and the Gravitex.. Although some areas were just fine..

Im going to see if it cures. May have to sand and do it all over.

962porsche 08-21-2017 06:23 AM

is it a single part etch primer ? my guess is it is and you used a spray can etch primer ?
if so that was the 1st wrong !
2nd you shouldn't use a etch primer under the chip guard . if you do your wait time is months not a few hours and thats only if you went with a two part primer .
then 400 grit is not enough tooth or cut to have the chip guard bite into the primer . 180 or 220 would be best for your sanding grits .
then it also looks like you sprayed to much to fast with out enough flash times between coats or you tried to do it all in one big coat with the chip guard . this will crack the chip guards like crazy too .
the top layer will dry faster then the under layer of the chip guard and as the solvents have to get out but can't thru a harder top layer it will push the chip guard apart to let it's solvents out as it drys .
as for not being a huge problem ???
it could be later on down the road . the chip guard could start to just flake and peal off .

High Life 08-21-2017 10:13 AM

It was a single stage etching primer. I used an aerosol - It was over bondo - which was over bare metal - and a bit over the old stone guard (sanded with 400) The stone chip (of course) covered the area I primed. The bondo areas seemed to be fine but not all. some areas dried and others didnt..

I did one coat of stone chip - once I saw that it was cracking I did not do a second coat.

70% is dry to the touch - 30% is tacky or sticky (after 2 days)

Appreciate the advice - I can learn from the mistake - at least it is in an area that is basically hidden - plus I noticed the stone chip covers a lot of imperfections..

So I assume the best course of action is to scrape and sand back to bare metal?
I tried removing some of the sticky (tacky uncured) coat - but it will need to be scraped off - I don't get pass the stone chip very easily.

Maybe scrape the tacky parts - sand, prime and respray the spots.. Or wait a month.. and see what happens..

High Life 08-23-2017 08:36 AM

Thanks for the insight.

I finished sanding down the uncured tacky spots and resprayed yesterday and the results look good.

Inside fender looks decent as well.

I plan on rattle canning a single stage red over the stone chip.

2 QUESTIONS if you would oblige (I understand if this is getting long)

1: - How much time do I need to wait to ensure curing of the stone chip before painting? (I haven't found anything on the U-Pol site nor is it on the label)

2: - Do I scuff a red scotch brite pad (then de-greaser) before painting? or just spray paint as is?

High Life 08-23-2017 09:24 AM

I think I may have answered my own question - found the tech sheet..

962porsche 08-23-2017 09:40 AM

looks good in the photos are you happy with it now ????

Dpmulvan 08-23-2017 11:51 AM

Rattle can paint is a waste of time and money

High Life 08-24-2017 06:10 PM


Originally Posted by 962porsche (Post 9711470)
looks good in the photos are you happy with it now ????

Thanks 962, I appreciate the advice you have put forth in this thread and others. Painting is not only a skill of chemistry but an art and talent that takes some time. I'm not that guy, nor interested in doing these types of things in the future. Unfortunately - like you stated in another thread, there is little interest in the insurance repair shops for doing this type of work. Restoration shops wont take on this type of stuff without a major bill or wanting to remove any work the owner previously did (I get the reason why). So in the end - I made the decision to DIY - I can weld, but paint is another animal..

I'm limited in technique, space, paint tools and experience to tackle paint projects. So to answer your question - (knowing my limitations):

Yes I'm happy. :)

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