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Re-building single-piece flat backs

   Much simpler than dome backs, the splitting of true flat backs is usually the result of shrinkage. Because the edges are firmly glued, the shrinkage often opens the back down the centre. If the break is clean it can be re-glued, but then the sides tend not to meet the edges. There are two or three options;

  • It is sometimes necessary to re-glue, cut the back in two, and then add another, often decorative piece down the centre.

  • Another possibility is to re-glue the back, glue back in place, then rout the edges to add edging, thus covering the lack of width.

  • Finally, if the shrinkage is not too severe, it is possible to re-glue, then round-off the sides to hide the lack of width.

   If the split is due to stress of over-stringing, it is often evident from damage around the tail, and the sides pulled out of shape. It is then usually possible to re-glue and refit the back, provided you re-glue loose side pieces, and clamp them to keep them in the correct place.

   Here is a flatback with a split right down the centre caused by lateral shrinkage. The edges are held in place by the glue, so the back gives along the grain somewhere else.

  A view from the inside showing that the struts are largely still in place. Fortunately the opening was not large or damaged, and possible to reglue.   Once reglued, the back was not short by much at either side, and the shortfall was taken up by rounding off the edges somewhat. Where this is not possible, other solutions must be found.    Here is the finished varnished back on the restored instrument.
In this waldzither, the back has shrunk but not split, it has just lost contact with the sides, and about 3-4mm short of material. It was relatively easy to cut down the centre and insert some decorative purfling to widen the back enough to be re-fitted. A crack clamp can be seen at the bottom, designed to pull the two sides together. Here it is whole again, big enough to fit, and being glued back in place.
   In this mandriola, the split in the back was untidy, and a previous attempt to re-glue it made it impossible to re-match the 2 sides easily. I decided to cut out the damaged section, and insert a decorative panel, with stringing.    First the ebony stringing was glued to each side. Once dry, the panel was glued to first one side and then the other. Care was taken to keep the outsides of the slightly different thicknesses level.    Here the back is whole again, with original struts re-fitted, and now wide enough to reach to both sides.    Fitted back on the instrument, I will keep it a different colour, rather than try to blend it in, as it will always be noticeable.