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Gold Top Paint Cracking while aging, not checking

PostPosted: Sat Jun 29, 2019 6:14 pm
by Derek Lenard
hey dudes and dudettes. Its been a long time, stuck on a problems not sure what to do. asking for some help.

I have a customer who wants an aged gold top. So I built the single cut carved top.

Here has been my steps:

Sanded maple top down to 600
applied Stew Mac White Prime (3 light coats)
then stewmac antique bronze let it site for a few days (4 coats)
Apply vintage Lacquer also from Stew Mac. (4 coats)
Let it dry in hot box and UV light kit for 4 days.
Start cycle of heating and cooling to get checks in freezer. nothing happening after 4 cycles.
Move to Dryer and desk cleaner upside down. (spray light and heavy combinations)
Lacquer and paint actually crack, cracks pull the gold away from the top. happened in a few spots.

This is the 2nd time I have done this with the same cracking. Its like the gold is not sticking to the primer.

I am frustrated, customer is frustrated.

Why is the paint chipping? doesn't make any sense to me. I have done this with other guitars and have had the desired results. I don't know what to do?

Re: Gold Top Paint Cracking while aging, not checking

PostPosted: Thu Jul 11, 2019 5:47 am
by Chris Richards
I feel your pain!...I do a lot of relic guitar finishes and it's always quite "hit and miss", some go really well and others just don't behave. I don't know what the Stewmac lacquer is but I always use nitro cellulose and a make that is low in plasticisers. I don't like using the pipe freeze/spray cooling as it is to violent and tends to produce a pattern that's more like the craze cracks on old pottery. Like you I put the guitar in a freezer then warm it gently afterwards although the paint finish has to be at least 3 months old, nowadays I use a number of techniques from scribing the checking lines and freezing and some other techniques..Here's a picture of a goldtop I did the other day that I was really pleased with although it did take a long time to do but other people have said that they can't tell it from a genuine one so that was very pleasing.

As for the adhesion problem you're having it sounds like the undercoat and gold are not completely compatible, the trouble is with a goldtop is that the gold can't really be sanded afterwards so the undercoat has to be perfect and not pretty smooth so there isn't much mechanical bonding.

Re: Gold Top Paint Cracking while aging, not checking

PostPosted: Thu Jul 11, 2019 7:18 am
by Brian Evans
My instinct is you are rushing things. Applying the nitro lacquer over the vinyl sealer is fine, but I would let the final finish cure for two to three weeks, then wet sand and buff as normal, and then go for the relic checking. I don't know if four days in a hot box is a replacement for two to three weeks of cure time. And you don't mention any buffing stage for gloss. I think checking depends on a quite hard and thin coat, and it sounds like yours hasn't cured yet. Also not sure why you wait four days before spraying the clear. Stew-Mac seems to recommend just going with their normal 2 - 3 coats a day until done. But I try very hard to avoid checking, so I'm probably wrong... :)

Re: Gold Top Paint Cracking while aging, not checking

PostPosted: Thu Jul 11, 2019 8:20 am
by Aaron Helt
Is the Stew Mac white prime vinyl sealer? If so I would skip it. Vinyl sealer doesn’t burn together with nitro. Test it out on scrap first.