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Open seam while varnishing

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Hey guys,

Most of the coats done on my varnish and when checking to see how dry the varnish was last night I noticed a bizarre new rattle noise while messing with the instrument (violin). I had a look through the endpin hole and can see some light either side of the neck joint between the ribs and the top. I can squeeze them closed with finger pressure no problems. 

I'm running through the things that could have caused this and corresponding actions.

1. I did a bad job of gluing the top on in the first place/bad glue batch

2. The violin's been in the sun to dry the varnish, maybe it got too hot

3. Perhaps some of the solvent in the varnish (gum turpentine) dissolved the hide glue?

For numbers 1 and/or 2 the solution is easy - just re-glue. Will need to wait a few weeks for the varnish to harden right up so I don't risk marking it with clamps. That or keep varnishing until it's completely finished and then fix it.

For number 3, I'm not sure what to do.

This happened to anyone else? Another possibilities is i didn't shave my top block quite enough or it swelled or something. Really not sure hahaha.

Thanks in advance.

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Why the seam opened is anyone's guess.  I doubt it was solvent from the varnish.  I would not continue to varnish without glueing the seam closed.  Do you use spool type clamps to glue the plates on?  You should be able to get away with clamping the seam without damaging the varnish.  Maybe use some parchment paper between the clamps and the varnish.  Good luck!

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I'd say a combination of 1) and 2).  The heat alone probably wouldn't cause the glue to fail, but it would drive out the moisture of the top and make it shrink.  I don't think varnish has much effect on glue, otherwise you'd have a ton of centerjoint failures.

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If I reading you right, my take is that yes heat can be very contributory, not from melting the glue, but causing rapid distortion in the material that will "boing! spring" things open...

again, simple fix....either get the glue pot out and heat some up, or just do a small microwave batch....use a thin "something" {I use strips of thin stiff plastic packaging, cut into "knife shape"} to work some glue into the area, making sure to get the contact parts wet....IF YOU ARE 100% sure that you made a sufficiently strong enough batch the first time around, you can just use boiling water instead of the glue will reactivate with the piping hot water, just work quick as possible and get the areas re-clamped and allow to dry....the challenge is to incorporate protective nonstick cauls or pads into the clamping so as to protect the fresh varnish ....I use quality wax paper folded up into little pads when I have something like this too deal with....'

A violin in the sun out side has to be "the right" kind of can very quickly get too hot, because it is a little box, it is like a little oven where the internal corpus temps can be very hot compared to outer surface temps

this is why uv lamps are best for control over such things, they put out the uv, but not tons of heat, particularly the newer led ones

just be glad you caught it now and not after you had the entire thing set up , you'd be wondering where that horrible buzz was coming from after playing the first note, which trust me, is much worse way to find it.

edit, if it was not obvious, if you do use glue and not water, make sure you wipe off any excess before you clamp with a dry damp cloth

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