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#1
08-18-2015, 09:59 PM
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Repairing a French Polished top
I keep reading that one of the advantages of shellac is that it makes it easy to fix the finish after a repair. Unfortunately, I've really been struggling to build the finish back up over a spot I took down to bare wood and to blend that spot refinish with its surroundings. I'm getting a darker halo around the spot that I stripped. Is there a way to avoid that?
Thanks! 
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#2
08-19-2015, 04:33 AM
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With French polishing, you should keep in mind the phases:
1) Seal 2) Pore fill 3) Build 4) Shine You'll have to build the shellac again in the area that you took down too much. Questions: - How did you take the finish down too much?? - What type of pore filling did you do?? Depending upon these factors, you may have to resolve yourself to a visible ring, or you may have to remove, re-surface, and start building again to avoid a visible ring.
__________________
---- Ned Milburn NSDCC Master Artisan Dartmouth, Nova Scotia
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#3
08-19-2015, 06:13 AM
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I always chuckle when I hear someone say that FP is easy to touch up.....because I know they have not done much repair work on it.
This is happening because you are concentrating on too small of a spot. You need to make the area you are working larger. For FP I usually figure 6-8 times the size of the actual area that needs repaired. Often times this means overcoating an entire surface on a guitar. The trick with any finish repair is blending the transitions. Prepping the damage properly will help with this. To deal with the halo you have formed you will need to sand it out or it will always remain. I use a small pink rubber eraser wrapper with 1200 wet/dry for these jobs. Lube the paper with a few drops of olive oil and carefully erase the halo. Then go back to polishing and work a larger area.
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#4
08-19-2015, 06:43 AM
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Thanks guys. Some great advice.
Ned, it's the guitar top I'm dealing with, so no pore filling. And it's a guitar I'm building for someone, not a repair of a previously finished guitar. So I don't want to "settle" for a less than good (for me--I'm no expert!) final product. I realized I had some scratches in a small spot after completing my second padding session. So I scraped delicately an area 2 or 3 times the size of the problem, fine sanded it, cleaned it up, then started padding again, focussing on that area. I'm using a relatively dark shellac, so initially the difference in shades was very apparent (obviously), but it's getting slowly better, although the halo is a problem. Thanks for the suggestion, Brian. I will try sanding the halo again. I did yesterday, but the paper gummed up so quickly. Maybe I should wait a few more days for the shellac to harden before trying to sand? I went down to 600 even, and it gummed up so fast I could not even see the difference where I sanded with a block.
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#5
08-19-2015, 08:08 AM
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I have found that the best way to repair a small area with French polish, is to practically ignore it. Work all around a large area with the spot in the periphery of the area you are working. If you work a small area, the buildup is greatest in the outside rim of the area you are working - thus the darker circle around the spot. Also, using pumice is a good way to get a build in the area you are repairing. I have often found that scratches, that I have made, are easily filled with pumice/shellac and a tiny bit of oil to keep it from sticking. Always spirit off if using any oil.....
__________________
Waddy
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#6
08-19-2015, 08:12 AM
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#7
08-19-2015, 09:36 AM
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Quote:
Brian gave some good advice. If you haven't scraped too much of the seal coat away, then you may be able to re-build with seamless tinting. You may have to lightly sand the overlap of the new shellac onto the old if it becomes too dark. If this is the case, avoid sanding into the area to be rebuilt.
__________________
---- Ned Milburn NSDCC Master Artisan Dartmouth, Nova Scotia
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#8
08-19-2015, 06:37 PM
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Been there done that many times, and have usually ended up sanding it all off and starting again. That is about the only way to make it invisible. When using dark shellac, or any other sort of colouring for that matter, it is very very difficult to match up the colours and you are better off saying stuff it, sand it off and start again. This applies especially for tops. In the time you spend trying to match up the colours and ending up with a less than perfect result, you are probably better off starting again. I know it is a pain and a lot of extra work to have to start again, but in the long run you won't regret it. It will look far far better than a patch up job. Nowadays if I find scratches I missed, I take a deep breath, say a few bad words, and it all comes off as a matter of routine. So it is important to look very carefully for scratches early on in the process so there not so much to come off. First or second coat you might even be able to patch it invisibly if the shellac is not so dark, later on it becomes next to impossible. Be really anal about looking for scratches before and after the first couple of coats. Different lighting can show up scratches you can't see under normal lighting. Sanding back to bare wood in a patch as you have done makes it really tough to make the patch invisible. It can end up taking hours and hours and the final result might look just barely acceptable, but my advice on a new instrument is to start again. Repairing an older instrument is another matter.
Last edited by peter.coombe; 08-19-2015 at 06:48 PM.
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#11
08-20-2015, 02:01 PM
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