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Nitro Finish repair(s)
http://luthiersforum.com/forum/viewtopic.php?f=10137&t=54503
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Author:  flemsmith [ Mon Oct 25, 2021 1:29 pm ]
Post subject:  Nitro Finish repair(s)

First guitar, this one had problems with bloom or blush around the end wedge which I posted before. Since my second is now my daily player, I thought numero uno should go for some repair work. I was worried about whether the edge of the lacquer removal would be obvious. After sanding the repair edges to a bit of a long bevel, sprayed with some shellac, 320 sand, unless I'm missing something, I feel pretty good about respraying that end...but
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I had originally done a crap job of wet sanding and polishing, so thought I'd try again, at least on the top. And my bridge install was a mess, have a thru hole fixture to use now, but the lacquer was disturbed around the bridge when I took it off. Peeled it back til adhesion felt solid, did some 320 hand sanding and a little more shellac. And now I'm thinking since I don't really know I'm doing this correctly, is there something else I should do before re-spraying with nitro? If it matters, I'm using Cardinal Gloss, about 20% thinner and mebbe 5% retarder. Thanks, Roy

Author:  Chris Pile [ Mon Oct 25, 2021 2:28 pm ]
Post subject:  Re: Nitro Finish repair(s)

I never used shellac between coats of lacquer. It inhibited the "melting in" of layers.

Author:  flemsmith [ Mon Oct 25, 2021 2:50 pm ]
Post subject:  Re: Nitro Finish repair(s)

Well dang, why didn't I ask earlier? Will denatured remove the shellac without hurting the cured lacquer?
Thanks for input Roy

Author:  Chris Pile [ Mon Oct 25, 2021 4:02 pm ]
Post subject:  Re: Nitro Finish repair(s)

Can't say. I don't use denatured alcohol.

Author:  Barry Daniels [ Mon Oct 25, 2021 4:06 pm ]
Post subject:  Re: Nitro Finish repair(s)

Yep, alcohol will remove lacquer. It might be better to try and sand the shellac.

Author:  flemsmith [ Tue Jan 18, 2022 4:16 pm ]
Post subject:  Re: Nitro Finish repair(s)

Just for ff up, I did resand and spray the top, focused mostly on the areas which delammed around the bridge. Not perfect, and after I reattached the bridge I got another small area of lifitng nitro, so I need to rethink the prep sanding process before I start nitro. Plus, my finish sanding and polishing still needs work....I did send in an application to Azwoodworkers hoping to get some in person experienced eyes for finishing advice. I'm having trouble telling I still have scratches left over from an earlier grit til after I get to the polish stage.
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I also took the end wedge back to bare wood to get rid of the blush (or bloom!?) caused by incomplete sanding of the titebond prior to lacquer. I think next build I'll try the LMI glue with a blacklight before I start nitro.
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Looks like I may be using this guitar (my first) as a process experiment vehicle, but for now I want to hear it again and compare the sound to number 2. Roy

Author:  Barry Daniels [ Tue Jan 18, 2022 4:19 pm ]
Post subject:  Re: Nitro Finish repair(s)

That last photo looks a lot better.

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