This cello had been in the shop for quite some time with a number of problems affecting the top and lower ribs. Since the instrument required a considerable amount of work and the customer was not in a hurry to have it back, the repair was postponed while I dealt with more immediate jobs. Eventually the customer needed the cello again, so it was time to tackle the accumulated damage. Several open cracks needed to be cleaned, glued, and reinforced where possible, one rib had separated from most of the top, and a substantial section of spruce was completely missing from the lower edge - enough that you could see directly into the cello. After repairing the cracks and loose ribs, I rebuilt the missing portions of the top and edge using molds and shop-made techniques to restore the original shape and overhang. The repaired areas were then finished and varnished. When the customer later asked if the missing section of purfling could also be recreated, I developed a method of laying out and scribing simulated purfling into the already finished repair. Because of the number of different problems involved, the following photographs and repair steps are divided into three sections.
- Clean the Cracks: Carefully clean the open cracks in preparation for gluing. I generally repair one crack at a time so each can be properly aligned and clamped.
- Glue and Align the Cracks: Work hot hide glue thoroughly into each crack, then clamp it while carefully adjusting the two sides so the surface remains as level as possible.
- Reinforce the Cracks: Normally I would install several cleats along these repaired cracks, but previous cleats were already occupying much of the available space, so only a couple of additional cleats could be fitted where they were needed.
- Reglue the Loose Rib: One section of rib had separated from approximately three-quarters of the end pin block. Work glue onto the rib and use the clamping setup shown to bring the rib and block securely back together.
- Align the Rib Crack: A small crack in the rib did not return completely flat when it was clamped, so I used a separate clamping arrangement to bring the two sides of the crack back into proper alignment.
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- Assess the Missing Edge: A substantial section of spruce was completely missing from the lower treble-side edge of the top, leaving an opening large enough to see directly inside the cello.
- Support the Top: Slip a thin piece of hard plastic beneath the remaining top and use two clamps to hold the top securely against the plastic.
- Make the Molds: Shape two Styrofoam molds to follow the inner and outer curves of the missing section.
- Protect the Top: Apply painter's tape around the repair area to protect the original varnish and provide a surface for attaching the temporary molds.
- Position the Molds: Glue the shaped molds to the protective tape and plastic guide, creating a channel that follows the original shape of the missing edge.
- Close the Channel: Block off the ends of the channel so the repair material will remain contained while it cures.
- Rebuild the Missing Spruce: Mix my wood-like casting material and pour it into the prepared channel to replace the missing section of the top.
- Remove the Molds: Allow the repair to cure overnight, then carefully remove the temporary mold material.
- Rough Shape the Repair: The newly cast section initially looks quite ragged because some of the repair material adheres to the mold, but the excess can easily be filed and shaped away.
- Clean Up the Rebuilt Edge: Carefully file and shape the newly created section to blend it with the remaining original top edge.
- Reglue the Top: Glue the repaired treble-side section of the top securely back onto the rib.
- Establish the Overhang: Because much of the lower edge was badly damaged and irregular, make a temporary form to establish the proper outline and maintain a consistent top overhang.
- Form the New Edge: Use a slightly thicker mixture of the wood-like casting material to build up and recreate the damaged portions of the lower edge.
- Shape the Edge: After the material has cured, remove the plastic guides and cellophane, then carefully clean, shape, and round the reconstructed edge.
- Align the Bass-Side Rib: Bring the bass-side rib back into its proper position and glue the back securely to the rib.
- Rebuild the Bass-Side Edge: Use the same general shaping process to reconstruct the damaged bass-side edge of the top.
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- Plan the Purfling: Normally I would recreate the missing purfling before varnishing the repaired edge, but since the area had already been varnished, I needed to develop a different method.
- Trace the Curve: Clamp a piece of plastic against the back of the cello and trace the curve of the edge onto the plastic with a pencil.
- Locate the Purfling: Use dividers to mark a series of reference points at the proper distance inward from the traced edge.
- Make the Outer Guide: Cut the plastic along the reference points and carefully smooth the resulting curve to create a clean guide for the outer purfling line.
- Scribe the Outer Line: Clamp the plastic guide onto the repaired top, align it with the existing purfling, and use a sharp knife to scribe the outer purfling line.
- Establish the Purfling Width: Smooth the opposite side of the plastic cut, then use a compass set to the width of the original purfling to draw a second parallel curve.
- Make the Inner Guide: Cut and smooth the plastic along the second curve to create a guide for the inner purfling line.
- Scribe the Inner Line: Clamp and tape the new guide into position, align it with the existing purfling, and use a sharp knife to scribe the inner line.
- Darken the Purfling: Carefully darken the two scribed lines to visually continue the original purfling across the reconstructed section of the top.
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