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Nov 13, 2023 - 2:19:35 PM
4 posts since 11/9/2023

After creating arches and hollowing the plates I find they warped and are no longer flat around the edge. Is this going to be a problem?

Nov 13, 2023 - 5:13:53 PM
like this

1398 posts since 3/1/2020

quote:
Originally posted by rosnekcaj

After creating arches and hollowing the plates I find they warped and are no longer flat around the edge. Is this going to be a problem?


It is a bit of a red flag. How long did your wood dry before use? Is there a chance it was not dry enough yet? Did the plates come into contact with moisture? Did the humidity change in your workshop significantly? Has the arching become distorted?

If the problem is in the wood itself, the plates may be doomed to warp substantially after assembly. That's something you definitely don't want. 
 

If, however, the plates have warped due to something else, there's a better chance of success. I would clamp them into a frame to gradually bring them back to flatness. Give it at least a few weeks to acclimate before removing from the frames and allowing them to sit for a while so you can check if they are staying flat. It's generally recommended to get the plates attached to the rib structure as soon as you can after doing the plate thicknessing--the longer they sit, the more that can go wrong. Ideally there won't be any deformation, but the world does not allow for ideal conditions very often. Carefully controlling the climate in your workshop and using wood that you can be sure has dried are a good place to start if you haven't already taken those steps.

Green wood is a major problem in factory instruments as it renders it impossible to rely on any stability. At a shop where I worked previously,  the owner bought a container full of Chinese violins but stored them for 20 years before touching them to allow them to actually dry before correcting problems and then varnishing them. The dealers who sell factory violins always swear that the factories are using European tonewood that's been aged naturally for 10+ years, but then you see sap droplets leeching out of the tops....

Edited by - The Violin Beautiful on 11/13/2023 17:15:24

Nov 19, 2023 - 6:21:09 AM

102 posts since 4/11/2022

quote:
Originally posted by rosnekcaj

After creating arches and hollowing the plates I find they warped and are no longer flat around the edge. Is this going to be a problem?


It happens to me every time. I'm not as fast as these other guys are (I am sure) but even if I was, and I got the back and top on the rib assembly before it had time to warp, I believe the plates are "trying" to warp after assembly just like they are before assembly. In other words you're going to have the stresses in the assembly either way. The plates are thin and have a lot of newly opened pores, so I think distortion is inevitable. 
        I haven't tried clamping a fiddle plate down to try and flatten it. I have tried to clamp down pieces of wood and let them dry and it didn't work very well. It may have helped some, but where it couldn't move enough it cracked. However, something like a fiddle plate that was flat at one time (and mostly dry already) might just flatten out. Other people on here say it works but I don't know if they have tried it and know for sure. 
       Are y'all talking from experience here? Do you know for sure that clamping a top or back down to a flat surface restores its flatness?

Nov 19, 2023 - 10:15 AM

1398 posts since 3/1/2020

quote:
Originally posted by fiddler135


       Are y'all talking from experience here? Do you know for sure that clamping a top or back down to a flat surface restores its flatness?


Yes. Depending on the amount of distortion, it may take months to get the plate to settle, but it does eventually.

Although it's a bit different, correcting arching distortion requires a lot of time and vigilance as well. I recently finished a cello restoration that took a year. Most of the time was spent correcting a spot where the arching had collapsed in the treble side due to an old soundpost crack that had come open and a previous repair that had failed. Because plates are so sensitive, it's necessary to be very gentle and move just a bit at a time until the plate shape matches the corrected arch of the plaster cast, and it's not enough for it to match; the plate must be able to hold shape for some time before it's safe to continue.

Compared to arching correction, re-establishing plate edge flatness is relatively easy. Many restorers believe that one should not fit a new bassbar without first establishing flatness at the edges. It's also pretty common to clamp a top to a frame as soon as it comes off and to keep the frame in place while fitting a bar (if needed). It's also common to lightly glue a "temporary  plate" to a rib structure to keep it from moving while the top is off. 

Edited by - The Violin Beautiful on 11/19/2023 10:16:59

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