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mamawelder

glueing cello soundpost crack

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I'm restoring an old cello. Nothing special it's a Franz Wilfer, which no one around seems to know anything about.

I've repaired it's edges and back and rib cracks.

I just noticed that from the outside I can see two very slight cracks in the soundpost area.

They are a bit more centered to the cello than where I would place a soundpost.

I can see two dents where someone had tried to force a too long soundpost in this area.

One crack is maybe 2 " long and the othe 3/4". They are visable from the outside but not inside.

Do I try to get glue into them somehow? If so how? Should I bother with cleats (studs)?

I was thinking of a soundpost patch , but I don't feel it really warrents one nor do I have any experience in doing that repair.

Besides it's not really at the spot I intend to fit the soundpost.

If I did make a patch I would probably invent some tooling to get the patch to exactly match the hollowed out wood.

Since I can't really see the cracks from the inside I'm not sure how to approach this dilemma.

I guess I can just leave them alone.

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What about fitting a post fairly tight so it would tend to open the cracks on the top, quickly tap in some fairly thin hot glue, then immediately knock the post over. With a proper fit post in the proper area you may never have another problem.

hr

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I'd do exactly that, but with super glue, let it dry for a couple of days so the solvent can all leave, and the glue shrink, and then scrape it down and polish it up. You didn't hear it from me.

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quote:


Originally posted by:
Michael Darnton

I'd do exactly that, but with super glue, let it dry for a couple of days so the solvent can all leave, and the glue shrink, and then scrape it down and polish it up. You didn't hear it from me.

Superglue (methyl-2 cyanoacrylate) does not contain a solvent. Hardening ('drying') takes place from the moisture (water) of the surrounding air forming methanal polymers. Best results obtained at RH between 45 and 65%. At a RH of 80% and higher a too fast reaction takes place with the risk of tensions and reduction of strength. Not any shrinkage is observed neither is a 'drying time' of days needed. Within an hour the joint can be charged.

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Why not hide glue? The superglue you promote is irreversible (unless you use high temperature or other agressive solvents). You may say there is no need to redo, but what if it's done incorrectly? Some repairers charge double if they have to redo a crack glued with such stuff (CA).

Some hot strong hide glue can simply be pressed with the finger into the 'open' crack from teh outside. And then put back the soundpost and remove the glue with a damp cloth. That's all.

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LOTS of luthiers use various formulations of super glue, particularly for crack repair. The stuff is quite thin and therefore prenetrates even thin cracks well. Thinning hyde glue to an equal viscosity would significantly reduce its holding power. It's not the right glop for assembling a violin, but it does have applications in repair where it excels. Also, if there's no evaporative solvent involved in curing, what's that potent smell all about, and what is it that people thin it with? -- sure does tickle the nose like something solvent based, at least partly. I'm willing to bet that a good many more crack repairs are done using super glue that anyone is willing to admit (at least in the violin world). I think if some hard-nosed repair person tried to charge me double for a re-repair of a crack done with super glue, I'd take a walk. Michael Darnton's advice is reflecting professional practice based on experience.

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Michael i assume you mean the industrial type of superglue(such as the non blooming type) and not the cheapo stuff.Also are you recomending it for post crack areas or just like in the case mentioned in the post where its away from the normal post position?

Also would it ever be used on more expensive instruments?

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Being that Michael is one of the biggest proponents of hide glue and correct repair methods, I personally made the assumption that this specific repair has everything to do with the quality of this specific instrument ( perhaps plywood as someone made reference to ). I don't believe he is at all advocating super-glue as the standard repair method, just in this example.

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I think one might find that the use of cyanoacrylate instant adhesives (super glop) in violin repair is a "don't ask, don't tell" kind of thing. Rumor has it that it beats out hide (hyde) glue for such repairs, but the very use of the term "super glue" in the same sentence with "violin" or any instrument in the violin family is a certain way to attract a lot of negative attention. I'm certainly not qualified to pass final judgement on this, and I suspect that the folks who are will stay mostly silent.

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Yes Fiddlecollector, the new format is lacking the "in reply to <person's username>" indicator of the previous format. I wish they could find a way to implement that, it was very helpful in understanding who was replying to whom.

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To Jacob, I currently have the back off this cello and I have had to put a patch in the back; not a soundpost patch, just patching a wide split in the wood.

I repaired the top's edges and a rib crack.

This is definately a solid carved cello. I wouldn't be messing with it if it were laminated.

To Michael. I guess your technique that you didn't tell me about, will require that I get the back glued back.

Once it's together I can put the soundpost in place to get the cracks to open a bit.

I see the reason for using the super glue.

It is so thin that it will wick in with a capillary like action similar to soldering.

It sounds like the pefect approach for my situation. I use the stuff all the time with bow repairs.

I know it'll be a good system for this.

I think hyde glue would be too viscus to get into these tight hairline cracks.

Thanks for the tip!

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quote:


Originally posted by:
robedney

LOTS of luthiers use various formulations of super glue, particularly for crack repair. The stuff is quite thin and therefore prenetrates even thin cracks well. Thinning hyde glue to an equal viscosity would significantly reduce its holding power. It's not the right glop for assembling a violin, but it does have applications in repair where it excels.
Also, if there's no evaporative solvent involved in curing, what's that potent smell all about
, and what is it that people thin it with? -- sure does tickle the nose like something solvent based, at least partly. I'm willing to bet that a good many more crack repairs are done using super glue that anyone is willing to admit (at least in the violin world). I think if some hard-nosed repair person tried to charge me double for a re-repair of a crack done with super glue, I'd take a walk. Michael Darnton's advice is reflecting professional practice based on experience.

If you smell cheese, do you smell the solvent? What solvent? Just a couple of thousends (could be easily more) of molecules reaching your sensors in the nose, telling you hey this might be cheese. The same for the superglue: the smell tells you that it's characteristic for CA. Just 'some' molecules of the monomer being a component of this glue.

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Hello Michael;

I can not believe my eyes, that you are suggesting super-glue to be used on a string instrument. Did you clear this with Jeffery? I can see by your last post that you are sticking your head into the sand, it should stay there till you start using Titebond Glue.

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As long as we're staying away from glue types...

Gregg's a pretty standard approach... although size and shape of the patch and the index cleating varies by the luthier. I often use two pointed (arrow shaped) cleats that index a notch in the patch stock rather than multiple cleats as the view is less cluttered.

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Since cracks and soundpost patches devalue the average instrument drastically, I'm curious what a 1734 Del Gesu that has as many cleats and patches as the one pictured in Gregg Alf's photos is worth compared to one that has no, or fewer, cracks.

Put another way, if a DG or Strad or even a lesser Italian is still priceless with damage, why is a good quality modern German or French instrument devalued by 50% by a crack or a patch? Is it simply the rarity of the DG?

It reminds me of the woman who told me once, when I was a cabinetmaker, "I only buy antiques". I replied, "I am making antiques, they just aren't old yet".

Also, on topic, I've experimented with CA glue in spruce cracks. It seems to work very well. When I dropped a jar of varnish on a nearly complete top I had made, and it cracked full length in 3 places, I glued it together with CA. I'm not going to use that top, but it seemed to work very well and is invisible where the cracks went together well.

Is it reversible? Well, there is solvent available, but I've never wanted to reverse a repair like that yet, so I don't know.

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quote:


Originally posted by:
jackc

Put another way, if a DG or Strad or even a lesser Italian is still priceless with damage, why is a good quality modern German or French instrument devalued by 50% by a crack or a patch? Is it simply the rarity of the DG?


Again... I will steer clear of the glue issue. I've said what I had to say about this several threads ago.

As far as depreciation, 45 to 60% (50% you mentioned) is reserved for a soundpost crack in the back. The crack being repaired in the del Gesu was in the top. Different thing...

Yes, a pure one (undamaged), of the same period and quality, would be worth more.

Yes, depreciation does tend to be age sensitive, within reason. It is not the "norm" for a new instrument to have a soundpost crack in the top, while it is the norm for an 18th century instrument. This tends to affect the market appeal for a new, yet damaged, instrument more than for an antique.

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