Repairing a cello button

A restoration method for creating a new button on the back plate

Makers reveal their special techniques

The cello is one of the most delicate instruments in the violin family. Acquiring a cello is a journey that involves extensive research, numerous questions and instrument testing. Given their substantial size and the significant investment required, cellos are often cherished for many years. This extended use, however, leads to various specific issues that demand regular maintenance and care.

One of the most common problems encountered during prolonged cello use is the breakage of the button. This is a highly delicate part of the instrument, and as a restorer I have frequently encountered this issue. Several factors can contribute to heel breakage, such as a poorly built neck, excessive hollowing of the purfling channel, and impact on the neck. I am currently working on an old cello with a broken button, whose owner has asked me to try to give a new life to his instrument.

The top of the back plate shows signs of wear

1 A poorly constructed neck joint at the top-block caused all the tension to be absorbed by the heel. Over time, this has led to the breakage of the heel. The dark patch at the top of the back plate shows a significant amount of glue that remained between the neck and the button on the back plate.

The excessively deep purfling channel

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2 The purfling channel has been excessively hollowed, leading to the weakening of the annual growth rings on the instrument top. This has finally resulted in the heel breaking. On one hand, the purfling channel is too deep, while on the other, the purfling itself has not fit snugly into the channel.

The outline and replacement maple

3 I start by drawing the outline on the back where I will graft a piece of maple to replace the broken heel. The new piece consists of a single piece of maple, to ensure greater strength.

4a Marking out the outline

4b Carving the outline

4 Next I carve the outline on the back plate, using a knife and a straight chisel. In this process I aim to carve out a wedge shape; the thicker part is next to the purfling and the thinner part at the end of the top-block. I then fill it in by gluing in a new piece of wood. When viewed from above, the infill has the shape of a trapezoid. In most cases, when the heel is broken, the purfling is also damaged and needs to be restored.

5a Planing the replacement maple

5b

5 To fit the piece of maple to the back, I prefer to use a plane. With it, I achieve perfectly straight and smooth walls, which I find impossible with a file. I thin the piece of wood sideways to attain the necessary dimensions, and to make it adhere tightly to the back.

6a Fitting the piece to the back

6b The replacement wood is clamped

6 After fitting the piece to the back (6a), I proceed to glue it using hide glue. I use a wooden support, which I place between the clamps and the back, preventing damage to the back during tightening. The clamps apply pressure at just one point (6b), and the wooden support helps to distribute the pressure across the surface evenly. It also aids in the actual process of bonding the two parts together.

Shaping the surface

7 I wait about 24 hours for the glue to dry completely. Then I begin to shape the surface where the top-block will be attached. For this purpose, I use my favourite plane and a straightedge to check the surface for any irregularities.

Re-adding the purfling

8 Finally I replace the missing piece of the purfling and attach the back to the sides. The heel is now restored and, after a few more operations, the cello will be assembled and ready to play.

The cello, as an instrument, demands care and attention, especially when it comes to a repair such as heel restoration. With a serious approach and a passion for craftsmanship, even the most delicate parts of the cello can be restored to their former glory. Working on the heel is not just a repair: it’s a revival of the instrument’s musical spirit and its owner’s connection to it. The art of cello repair is an opportunity to keep instruments alive and pass them on to the next generation of musicians with soulful value and beauty.