Sanded thru the Top?

The Achilles' Heel of Luthiery
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TXFlatSix
Posts: 15
Joined: Wed Jan 04, 2017 1:30 pm

Sanded thru the Top?

Post by TXFlatSix »

Good morning,

I have been working on my 3rd guitar build and things have been going reasonable well. Making a few mistakes along the way but my competency has been improving. Decided to give Royal Lac a try and am really pleased with how beautiful the finish looks. I padded it on. Started with the Seal Lac, then Royal Lac, then cut 50/50 Royal Lac and sanding and buffing. Many thin coats.

My question regards a section in the upper bout. When buffing I noticed a small section which didn't buff out. The rest of the guitar is buffing out nicely. I have attached a photo but it is incredibly difficult to get a good picture of it. The area is about 2" in diameter. I have been trying to figure out what to do. I have a feeling I may have sanded thru the finish but as strange as it sounds I just am not sure.

Any suggestions?

Dave in TX
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phavriluk
Posts: 554
Joined: Mon Jul 09, 2012 9:49 pm

Re: Sanded thru the Top?

Post by phavriluk »

I am offering a guess of a solution which I HAVE NOT TRIED: dampen the universal dry lint-free cloth with naphtha and wet the spot and surrounding area. See any differences? I assume that if the surface has a finish, the naphtha won't penetrate, and if the surface is compromised, it will.
peter havriluk
TXFlatSix
Posts: 15
Joined: Wed Jan 04, 2017 1:30 pm

Re: Sanded thru the Top?

Post by TXFlatSix »

Peter, thank you that's a really good idea. I used StewMac's fine polish so I might need to make sure any residue from that is removed first. Or perhaps the Naptha will do it. Boy I don't want to mess up this guitar finish!
TXFlatSix
Posts: 15
Joined: Wed Jan 04, 2017 1:30 pm

Re: Sanded thru the Top?

Post by TXFlatSix »

The surface is compromised so I am going to attempt to fix the area without sanding the entire top and starting over.

Dave
johnnparchem
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Re: Sanded thru the Top?

Post by johnnparchem »

I am not an expert at refinishing in any sense so take anything I say as just my own personal experience.

I have sanded through on spruce and tried to repair it. What I found is that spruce starts to change color right after sanding due to exposure to light. Sanding through the finish into the wood removed that color from the spot sanded through. I have never been able to blend in the repair so that it disappeared and have ended up removing the finish and refinishing.

I use paint removers to strip off finish on the top as it is really easy to over thin the top when sanding off finish. If you do try and touch up apply finish to a large area and do not concentrate of the problem area. Extra attention to just the sand through area tends to make it show up more than less. On a light wood everything shows up.
TXFlatSix
Posts: 15
Joined: Wed Jan 04, 2017 1:30 pm

Re: Sanded thru the Top?

Post by TXFlatSix »

Yeah I think the odds aren't in my favor. I will give it a try and if it doesn't work out then I can remove the finish on the top anyway and redo. It's a shame since the finish looks great otherwise.
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TXFlatSix
Posts: 15
Joined: Wed Jan 04, 2017 1:30 pm

Re: Sanded thru the Top?

Post by TXFlatSix »

I fixed the finish this weekend. It took much more sanding than I thought...or perhaps I was just worried that I would sand thru the finish again. In the end I did get it smooth and it polished out nicely. I can confirm however that there is a slight color difference where I sanded thru originally. It's just ever so slightly "yellower" than the surrounding area but you have to look hard to see it and you might not even notice if I didn't point it out. I think I am going to just let it cure for a while and see how I feel about it.

Thanks

Dave
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