Scratches in shellac

The Achilles' Heel of Luthiery
John J
Posts: 296
Joined: Wed Nov 26, 2014 7:52 pm
Location: Saint Paul, MN

Scratches in shellac

Post by John J »

Soooo. My Koa and cedar got scratched up on the right upper bout pretty good. I broke it down and sanded the scratches out -they ran pretty deep. Trouble is now I have an area that doesn't blend in. These pics just after I applied a little Seal Lac to see where I was. Finish is Royal Lac over Seal Lac padded on. Will I have to sand the entire top back down to make it look all even? Thanks for any advice on this.
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phavriluk
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Re: Scratches in shellac

Post by phavriluk »

What's the rest of the top look like? All I can see is the repaired area and the region under the fingerboard.
peter havriluk
John J
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Re: Scratches in shellac

Post by John J »

Looks like this.
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Diane Kauffmds
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Re: Scratches in shellac

Post by Diane Kauffmds »

I feel for you for sure. My newly built 00 had a couple of dents that I hesitate to even try to correct.

I had a tiny dent by the bridge right after I built it. I removed the shellac, so I could use the soldering iron with a wet paper towel, to pull the dent out. Little did I realize how HARD it is to build the finish back up in that one spot, then evenly distribute it over the whole guitar. But, I was able to do it.

I was able to even up the repair area by building shellac in the area repaired, then using the same shellac impregnated pad, adding alcohol as needed (no shellac). I rubbed out the whole guitar, using alcohol only on the shellac mouse, until it blended. It took a while, but I got it blended. I used medium pressure, then as it started distributing, I lightened the pressure. I started in small circles, like french polishing, then I switched to doing the entire length, then across the grain. I switched back and forth until I got it as even as possible. It took a couple of days, but I eventually evened it out.

However, I still need to know how you polish by the fretboard or bridge and make it look neat without buildup or wipe marks; this is my biggest problem.

I would like to know how you fix a dent in a french polished guitar. I know that the shellac will be ruined by the heat, but do you remove the shellac first or after the dent is fixed? Is there an alternative to fixing a little dent in a fp guitar?
Diane Kauffmann
Country Roads Guitars
countryroadsguitars@gmail.com
Danl8
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Location: Chadds Ford, PA

Re: Scratches in shellac

Post by Danl8 »

Just based on the pictures, I would try blending (sanding) the harder edges or areas of greater contrast and let the affected areas darken a bit (photo-oxidize) before finishing. Over time color shift should become less noticeable. I have had this issue in the past with using cedar for lute tables (not the best wood to use there).
Danl8
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Re: Scratches in shellac

Post by Danl8 »

Diane Kauffmds wrote:...I would like to know how you fix a dent in a french polished guitar. I know that the shellac will be ruined by the heat, but do you remove the shellac first or after the dent is fixed? Is there an alternative to fixing a little dent in a fp guitar?
I don't necessarily have the right answer, but I have some recent experience creating small dents (much to my chagrin) and fixing them with shellac. I take 2 mL 3# cut in a small condiment cup and let half of it evaporate. The shellac is then quite thick and dropped into the dent. In a session or two, the shellac dries hard above the surface level and gets scraped with a straight razor blade and fine sandpapers until its ready for spiriting off.
Diane Kauffmds
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Re: Scratches in shellac

Post by Diane Kauffmds »

Danl8 wrote:
Diane Kauffmds wrote:...I would like to know how you fix a dent in a french polished guitar. I know that the shellac will be ruined by the heat, but do you remove the shellac first or after the dent is fixed? Is there an alternative to fixing a little dent in a fp guitar?
I don't necessarily have the right answer, but I have some recent experience creating small dents (much to my chagrin) and fixing them with shellac. I take 2 mL 3# cut in a small condiment cup and let half of it evaporate. The shellac is then quite thick and dropped into the dent. In a session or two, the shellac dries hard above the surface level and gets scraped with a straight razor blade and fine sandpapers until its ready for spiriting off.
Thanks. I've heard of drop filling, but I wasn't sure how to do it. I tried to do it but with the regular 2# cut. Needless to say, it never really filled the dent and I ended up with more to clean up than I wanted.
Diane Kauffmann
Country Roads Guitars
countryroadsguitars@gmail.com
MaineGeezer
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Re: Scratches in shellac

Post by MaineGeezer »

Duplicate.
Last edited by MaineGeezer on Thu Feb 18, 2016 11:03 pm, edited 1 time in total.
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MaineGeezer
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Re: Scratches in shellac

Post by MaineGeezer »

Yes, I've tried drop filling with (about) 2# cut and it doesn't work. It spreads out too much. The edges of the puddle end up higher than the center when the shellac drop dries, and one is left with a raised ring of shellac that is very difficult to get rid of.

Next time I'll try a much more viscous drop, as suggested.

As far as blending in a repaired area....I haven't had much success with that, either. The best I've been able to do is smooth it down with 0000 steel wool (n.b. LMI's 0000 steel wool is finer and much better quality than what is sold at your local hardware store) and then rubbing on more shellac with a pad. If you're lucky the color will blend in. If you used two different kinds of shellac, good luck duplicating what you did the first time!
Don't believe everything you know.
Anything is possible if you don't know what you are talking about.
When things are bad, try not to make them any worse, because it is quite likely they are bad enough already. - French Foreign Legion
Ben-Had
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Re: Scratches in shellac

Post by Ben-Had »

Your best bet is to sand the top back and refinish. That spot will NEVER go away any other way.
Tim Benware
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