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whatwasithinking
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 Posted: Fri Sep 13, 2013 10:00 am Post subject: |
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It's looking more and more like the fun is only beginning. The stripping was the easy part.
Question: is there any reason the center of a soundpost patch would be substantially thicker than the edges? The one on this instrument is about 1mm thicker at the center. About 6mm vs 5mm. Poor shaping, or intentional thickness augmentation? Or maybe the repairer didn't carve out a bed... |
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ctviolin
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| Posted: Fri Sep 13, 2013 12:11 pm Post subject: |
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| whatwasithinking wrote: | It's looking more and more like the fun is only beginning. The stripping was the easy part.
Question: is there any reason the center of a soundpost patch would be substantially thicker than the edges? The one on this instrument is about 1mm thicker at the center. About 6mm vs 5mm. Poor shaping, or intentional thickness augmentation? Or maybe the repairer didn't carve out a bed... |
A sound post patch is an interesting thing.
Well, in a normal sound post patch, on the inside (surface) of the plate, where a soundpost crack had occurred, the center of the patch USUALLY is thicker, because the place where the patch goes should be carved out where the thicker center of the oval patch is located under or very near the position of the sound post, essentially, for strength and elimination of a crack in the original thickness of the belly (or back) wood,.
The crack will be eliminated by both the thick part of the patch, and the edges of the oval patch which thin out gradually... any remaining portion of the crack, that may continue beyond the position of the post is simply glued shut and perhaps cleated - right?
The part of the patch that can be seen on the inside surface of the instrument shouldn't rise above the natural inside surface of the plate at all - see what I mean, the thicker part of the patch is not seen but is hidden by the fact that it has been submerged in the thickness of the plate, creating an area of greater strength in that portion of the patch - where the crack was most "stretched" by the exact location or position of the post.
Perhaps the repairer didn't carve out the bed, as is usual for a typical soundpost patch.
But such patches are rather involved, and may require a cast of the belly, or of that portion of the belly, in order to clamp against, keeping the original shape of the outside surface of the belly correct when the soundpost patch gets glued and clamped in.
Is there a sound post patch on the belly of this cello?
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Last edited by ctviolin on Fri Sep 13, 2013 12:37 pm; edited 1 time in total |
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ctviolin
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| Posted: Fri Sep 13, 2013 12:14 pm Post subject: |
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Sorry.
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Last edited by ctviolin on Fri Sep 13, 2013 12:37 pm; edited 1 time in total |
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whatwasithinking
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| Posted: Fri Sep 13, 2013 12:23 pm Post subject: |
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| ctviolin wrote: | | Is there a sound post patch on the belly of this cello? |
There is. I've seen the Weisshaar pages on this repair, and read most of the posts here and at MN about the topic, but haven't actually done one. But this one doesn't look right, and I wondered if it's likely that it was a slap-dash job without the proper preparation. If so, should I attempt to make any corrections, or just leave it as-is? Seems tempting to thin the patch a bit, but what if it's already thin?
Even worse, there's a crack in the back. Yeah, I should have noticed it immediately--but I didn't. So it really needs still another patch. Economically, it's not worth the repair, but this is for "fun," so what does it matter? I can only guess that, following the belly repair, the same old soundpost was forcefully reinserted, causing the back to crack. Nice, huh? |
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Chet Bishop
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| Posted: Fri Sep 13, 2013 12:27 pm Post subject: |
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This will not help the actual repair process, nor the decision-making, more than likely; but one thing I determined very early was to treat each repair as if the violin was priceless, and count the excess time and effort as tuition paid. It is almost always a good learning experience.
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ctviolin
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| Posted: Fri Sep 13, 2013 12:55 pm Post subject: |
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| Chet Bishop wrote: | | This will not help the actual repair process, nor the decision-making, more than likely; but one thing I determined very early was to treat each repair as if the violin was priceless, and count the excess time and effort as tuition paid. It is almost always a good learning experience. |
Yes - I believe that this is the correct answer. Do a correct repair, which would entail separating the belly from the rib assembly, and putting in a "correct" patch if a poor attempt was made originally.
Oh well, such is the price of buying a cello with poor work already done on it. What do you have to loose by doing the correct work?
Nothing lost - much gained - work you will not regret doing or attempting to do, in my opinion.
Unfortunately when you buy something that has been "half done" and half done incorrectly, there is often much additional repair work involved - such is the case for many such jobs.
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whatwasithinking
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| Posted: Fri Sep 13, 2013 2:57 pm Post subject: |
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You've both convinced me of the value of doing a correct repair.
Any suggestions for removal of the patch, since it seems to have been glued with something other than hide glue? It's some kind of water-resistant and flexible adhesive. I fear that I may damage the original wood by attempting a removal. |
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Chet Bishop
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| Posted: Fri Sep 13, 2013 5:06 pm Post subject: |
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Finger planes until quite thin, then a sharp scraper?
Or experiment and discover what solvent will remove the glue. (Acetone for superglue, vinegar for aliphatic resin glues, water for hide-glue, etc. (I don't know of a solvent for gorilla glue, sorry...) There is even a commercial product that claims to remove "any" glue. ("Glue Goof-Off"? some name similar to that. I have never used it.)
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Last edited by Chet Bishop on Sat Sep 14, 2013 1:35 pm; edited 2 times in total |
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whatwasithinking
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| Posted: Sat Sep 14, 2013 12:27 pm Post subject: |
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| Thanks, Chet. I'll start with the finger planes. |
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Mat Roop
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| Posted: Sat Sep 14, 2013 11:47 pm Post subject: |
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If it was white or yellow carpenters glue, use heat!
Heat the area as hot as you can with a hair dryer and the glue should soften, if there is no risk of other damage, it may be quicker to us a hot air gun of the type used for paint removal( it gets a lot hotter). Then find an edge and pry the patch off ... let the patch separate slowly from the top. At this point the glue is soft but slow to give.
Once off, you have the problem of removing all traces of glue... I use "de-glue Goo " It works wonders on white or yellow glue.
http://de-gluegoo.com/
Once you get the glue off... you may want to reshape the patch hollow.
Cheers!... Mat |
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Chet Bishop
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Mat Roop
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| Posted: Sun Sep 15, 2013 3:20 pm Post subject: |
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The nice thing about this De-glue goo is that it does not seem to swell the wood nor affect the varnish ... at least not on the several instruments that I have used it on.
Apparently it is a mixture of acetic acid and starch.
Cheers, Mat |
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whatwasithinking
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| Posted: Sun Sep 15, 2013 9:02 pm Post subject: |
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| Thanks, Mat. One thing about the patch is that I believe it's only there to fill in a gouge created by the soundpost, and not to fix a crack. So, it's possible it's nearly how it should be, except for the thickness. Does this seem reasonable? The sad thing is that the repair probably led to the crack in the back. |
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I couldn't recall the name. Thanks, Mat!