Thursday, 13 February 2014

Cello Repair 11/2013

This cello belongs to a friend who played it in his school's Chinese Orchestra when he was younger. It had survived what I believe was a relatively major fall that saw the fingerboard take the brunt of the impact.

Fortunately, most of the force of the fall was used to break the glue holding the fingerboard to the neck, resulting in the fingerboard breaking off and taking a small chunk of the neck it it. For those who don't know, violins are held together by hide/animal glue, which is designed to give way in some situations before the wood cracks.

Other than having a small chunk of its neck torn off, the instrument suffered no other forms of structural damage Gluing the fingerboard back on is (and was) a messy and frustrating business as it tends to slip and slide, smearing glue all over the place (in any case, dried hide glue is easily washed off with hot water).

One other complaint my friend gave me was that he did not like the sound of his instrument (before the fall)! Besides new strings (which the instrument was in dire need of), I noticed that his bridge was also thicker than normal. Violin shops sometimes leave the bridge (and the entire violin for that matter) a bit thicker than recommended on student instruments to negate the lower quality of the wood used as well as to allow the instrument to better survive repeated abuse.

However, a thick bridge muffles the sound of an instrument as it cannot efficiently transfer string vibrations to the body of the instrument. On the flip side of the coin, an overly thin bridge also does detriment to the tone of the instrument and will also warp with time (due to pressure from the strings).

Thinning the bridge (I used a belt sander) tested my patience as bridge thickness is measured to an accuracy of 0.1mm (using digital calipers) and it is very easy to over-thin the bridge. Overall, I had to thin the thickest parts of the bridge by around 1.2mm and the thinner parts by as little as 0.3mm. The results were quite satisfactory as constant checking ensured that I did not shave off too much (a lesson learnt from carving a violin bridge for the first time).

Putting everything back together, the cello spoke again after many years in storage. A final verdict on the tone (normal student grade tone, rounded, slightly bright, a little thin) however, will have to wait for new strings!

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