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Poly over poly issue

 
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horaxe



Joined: 17 Aug 2011
Posts: 57

PostPosted: Tue Oct 31, 2017 11:29 pm    Post subject: Poly over poly issue Reply with quote

Got a squier bullet for refinishing. It was in fiesta red mint co diction.
I wanted a candy cola finish.

Long story short, scuff sanded the finish and painted over it with several layers of the color, followed by clear coat. Wet sanded and polished and all was well.

But the buffer caught an edge and pulled back a huge chip of paint.
Now I have found a few spots where the paint is chipping and showing fiesta red.

I was hoping to avoid sanding back as I wanted the red to show through a bit.

However, I will have to repaint I think. Should I have done a coat of poly based sealer prior to the new color, or should I have primer over the fiesta red?
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BrightKJ



Joined: 13 Sep 2008
Posts: 342
Location: Midlothian, VA

PostPosted: Wed Nov 01, 2017 5:53 am    Post subject: Reply with quote

Poly finishes require a mechanical bond to adhere to the surface. Being a poly (plastic) finish, the layers of paint don't melt into one another and it's not going to wear through like lacquer, so the only way the red is going to show through is if your new finish chips or flakes off.

You really don't have much of a choice but to sand it back and repaint it. If you're going to use poly, I would sand all the way back to wood, use a poly based sealer/primer and then paint.
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horaxe



Joined: 17 Aug 2011
Posts: 57

PostPosted: Wed Nov 01, 2017 7:56 am    Post subject: Reply with quote

I thought you could scuff the clear coat to make it more adhesive for the paint?
Is that incorrect?
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BrightKJ



Joined: 13 Sep 2008
Posts: 342
Location: Midlothian, VA

PostPosted: Wed Nov 01, 2017 1:46 pm    Post subject: Reply with quote

Yes, that is correct, but it still isn't the same or as strong as the bond to the underlying surface. It also is dependent on compatibility with the original type of paint, how clean it was, how long it had to dry before you start buffing... lots of variables that could have led to your problem. Poly over poly will always be more susceptible to chipping/flaking.
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marksound



Joined: 15 Aug 2005
Posts: 16669
Location: OKUSA

PostPosted: Wed Nov 01, 2017 2:38 pm    Post subject: Reply with quote

I'd always use primer if there's an existing finish.
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BrightKJ



Joined: 13 Sep 2008
Posts: 342
Location: Midlothian, VA

PostPosted: Wed Nov 01, 2017 4:14 pm    Post subject: Reply with quote

marksound wrote:
I'd always use primer if there's an existing finish.

+1 to the above

If you can find one that is or has an "adhesive promoter", that's even better.
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ladyfinisher



Joined: 21 Feb 2013
Posts: 398
Location: California

PostPosted: Sat Nov 04, 2017 12:47 pm    Post subject: Reply with quote

It sounds like there may have been a film on the old finish or the two were not compatible. I use a product called Acrylaclean to wipe the surface down before spraying. It will remove anything on the surface. Maybe the sanding grit was too high and there wasn't enough for the new paint to bite to.

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