One of the more complex repairs that can befall a string instrument is a crack in the top and or bottom plates right where the sound post is. This sound post crack can rapidly propagate from here to the full length of the violin or cello if not attended to in a timely manner. The sound post carries the rocking of the bridge down to the bottom of the instrument and is critical to an instruments sound. A tight sound post, either through incorrect fitting, climatic change can sometimes lead to this injury. Though more often than not a sound post crack arises from misadventure where the weight of the instrument falls on the bridge causing the top plate to flex right on the sound post.
Repair for a sound post varies from glue it up and pray, cleat the area most near the sound post (and pray) or fit a sound post patch. Sometimes i take these approaches depending on the injury severity, value of instrument and the wishes of the owner/wallet. If it doesn’t last more expensive opts can still be undertaken later As one of the more high pressure areas of the instrument and under a lot of mechanical vibration (music) it also has forces acting outwards rather than inwards, so the natural arching structure of the instrument can’t really help it. A sound post patch covers the area of high pressure and surrounding area.
On a student level instrument an externally applied patch (but on the inside) is often the most cost effective repair ( though abhorred by purist luthiers). Its attractive because it can be applied through the f- hole so the top doesn’t need to come of the instrument (which takes time, and time is money), and being a patch on top of the existing plate (but on the inside) relatively quick to apply. Whilst it’s on the inside its invisible to the naked eye, but it adds thickness to the instrument and so effects the sound to a fair degree. This kind of patch is most often seen on a student cello, where on a bigger body it has less influence on the sound. I sometimes do this repair as the traditional repair cost can exceed the value of the instrument.
The traditional sound patch repair requires the top to come off the instrument, and the inside of the top of bottom plate is relief carved down, inside this shallow “hole” is where a new patch is fitted. As you can imagine the new piece needs to fit the hole as close as possible to ensure that there is no void that will influence both strength of the patch – but also critically the sound and so can take quite some time to fit. Given the thickness in this area of a violin is ~5mm there is not a lot of wriggle room for error and also one of the key challenges is to preserve the shape of the existing arching of the instrument. Often a plaster cast or a shaped support structure is used during the fitting process.
Other repair services
- Cello Bridge Replacement
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- Edge repair on violins and cellos
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- Violin fingerboard repairs
- Violin Pegs and peg box repair
- Violin Repair cost
- Violin Service
- Violin Sound Post replacement
- Violin Warranty
Blogs about Repairs
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