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Tostra

Clean crack to reglue?

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Hi people :-) 
I'm repairing a fairly old violin that I found in a local antique store. It's not very special, but it seems well built and I expect it to have a nice tone. Besides, I'm still learning. I've repaired a couple of violins before, but I don't want to work on anything too good yet.
The top had two cracks. I glued the first one and it went quite well. The other one, however was more difficult. The wood had moved over time, so the crack was wide open and required quite  bit of clamping to stay together in the right position. I set it to cure overnight, but one of the clamps must have gotten loose, because the crack is now open in the middle and perfectly closed in the sides.

My question is: how do I remove the now hard hide glue in the crack that's preventing it from closing rather than holding it together? Will it be sufficient to heat up the area with a heat gun and reclamp it? would that daamage the wwood or the finish?
I've tried scraping carefully with a knife, but it's not very effective, and I can't reach the "corners" where the crack goes from open to closed.
I was also considering a damp brush, but I don't know if softening/removing the glue would take so much water I'd ruin the wood...

Is there any good way to do this? And yes, I will be more careful next time with my clamping :-/

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If you used HHG, carefully applied water will do the trick for you. I can't recall which member has posted pictures of his "Glass of water/String Wick" procedure but that is one way. Or you can use a small brush and water and a fair amount of careful time.

If you used anything other than HHG..... all bets are off.

 

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1 hour ago, Michael Jennings said:

If you used HHG, carefully applied water will do the trick for you. I can't recall which member has posted pictures of his "Glass of water/String Wick" procedure but that is one way.

I think that was Jacob Saunders.

Some other tips: To help prevent water from getting where you don't want it, you can apply masking tape on each side of the crack. Be sure to use a tape with a weak enough adhesive that it won't pull off varnish (on the outside) or wood (on the inside) when it is removed.

You can delay the moistened string or thread from drying out quickly by putting plastic cling film over the area.

 

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3 hours ago, Tostra said:

Hi people :-) 
I'm repairing a fairly old violin that I found in a local antique store. It's not very special, but it seems well built and I expect it to have a nice tone. Besides, I'm still learning. I've repaired a couple of violins before, but I don't want to work on anything too good yet.
The top had two cracks. I glued the first one and it went quite well. The other one, however was more difficult. The wood had moved over time, so the crack was wide open and required quite  bit of clamping to stay together in the right position. I set it to cure overnight, but one of the clamps must have gotten loose, because the crack is now open in the middle and perfectly closed in the sides.

My question is: how do I remove the now hard hide glue in the crack that's preventing it from closing rather than holding it together? Will it be sufficient to heat up the area with a heat gun and reclamp it? would that daamage the wwood or the finish?
I've tried scraping carefully with a knife, but it's not very effective, and I can't reach the "corners" where the crack goes from open to closed.
I was also considering a damp brush, but I don't know if softening/removing the glue would take so much water I'd ruin the wood...

Is there any good way to do this? And yes, I will be more careful next time with my clamping :-/

HHG means hot hide glue.  I would warn the OP that the thread linked by Michael is a collection of aggressive organic-solvent-based approaches for removing other glues than hide.  Ignore it for the moment, but study it later, it's useful.

What Jacob linked should start you down the path of the straight-and-narrow (pun intended).

Removing the glue with soaked strings will do you another favor.  It's quite possible that one of the problems that made it reopen is shrinkage along the crack.  Rehydrating the glue to remove it may make the wood swell enough to straighten out for regluing.  If it doesn't look straighter after cleaning, soak it overnight with a thicker string, and try again. :)

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5 minutes ago, Violadamore said:

HHG means hot hide glue.  I would warn the OP that the thread linked by Michael is a collection of aggressive organic-solvent-based approaches for removing other glues than hide.  Ignore it for the moment, but study it later, it's useful.

Agreed. Most of my comments in that thread were aimed at weakening non-traditional adhesives. Any solvent which is likely to "remove" epoxy or cianoacrylate is likely to do high violence to varnish.

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OOOPS>>>>>>>>>>>>>>>>>>>> APOLOGIES to Michael!!!! :wub:

That thread was linked by George.  Mea culpa, mea maxima culpa.......

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