EXAMPLE OF RESTORATION:
The instrument is a violin by Charles-François Gand, also called “Gand Père”. It was damaged in an accident a long time ago. One can see numerous fractures on the belly where the sound-post had gone through in the past. The instrument was restored then, but now the cracks are very visible and some have widened. It is worth restoring this violin again to prevent its condition from getting worse.
I will now describe one way to restore the sound-post area of the belly. After takingthe belly off the ribs, I make a plaster cast and rectify the little arching imperfections.
THE SOUND-POST WENT THROUGH THE BELLY
Then, I remove the old sound-post patch. I wash the area with hot water. The old cracks open and some little pieces of wood loosen. After the area dries, I readjust the cracks, glue them and do the same with the little spruce pieces that I can still use (the original ones for sure). A hole remains due to lack of wood.
Because the belly is very thin (a few tenths of a mm) in this area after the removal of the sound-post patch, I adjust and glue on a thin patch (1 mm) from below to strengthen the area and be able to work on it.
To compensate for the lack of wood, I take a chip of wood with a gouge from the inside of the belly just above the area to be restored and glue it on a piece of spruce to strengthen it. The chip has exactly the same characteristics (width of growth rings, colour) as the missing wood. It will match the surrounding wood seamlessly. I adjust and glue another spruce chip of the same quality in the place of the chip I just took off.
Now, to be able to fit the chip I have just taken to the site of the missing wood, I cut through the patch I added earlier, cutting vertically along the veins of the wood on two sides and in a dovetail perpendicularly to the veins (along the end-grain) on the other two sides. Then, I adjust and glue the chip from the underside of the belly, and finish the surface with a wood scraper. To complete the repair, I add a new sound-post patch beneath.
After restoring the rest of the instrument (other cracks, edges, among other things), I re-glue the belly on the ribs and touch up the varnish.
This does the trick!