. . . is straightening out a badly distorted back. Once a flat sheet of wood, the back now resembles an undercooked potato chip. After removing the back from the rim and braces from the back, the resembence is even more profound.
This morning Shin, Cary and I kicked around several ideas to address the problem. I went back into our storeroom and found the 200" radius concave jig on which the back braces were originally glued. We made up a few radiused dummy braces and pressed the back into the jig using spring loaded go-bars and a go-bar deck.
Shin spent a good part of the morning heating the inside face of the back with a paint stripper (the red thing in his left hand: think hair dryer on steriods), and occassionally wetting the surface with a spray bottle.
I don't know how hot the back got, but my recommendation to Shin was to heat it as close to the temperature required to bend sides as possible, but to stay below the temperature required to strip paint, (ie. the finish on the other side.) We decided to leave the back under tension overnight and check results in the morning. This operation may require several re-applications.
Tomorrow we will separate the purfling lines that border the back strip. Glue, debris and whatnot have gotten into the gaps that opened up when the guitar received a soaking. After purflings are feed, we hope the two halves of the back can be re-mated with minimal pressure.
Several strategies for applying presure were discussed, but that decision will have to wait until tomorrow.
The afternoon was spent watching paint dry, or the inverse of that experience. The Banjo Killer was originally assembled with aliphatic resin (yellow) glue. Shin was amazed to learn that this glue can be dissolved with ordinary paint stripper. He spent several hours cleaning old glue from rims, blocks, braces, etc. The sides were masked to prevent accidental stripping of original finish.
We also used a little household bleach to clean some of the darker areas of mold on the back and sides. We plan to use bleach more liberally on the top and the braces, as spruce is supposed to be white, anyway.
Check out the "high tide" marker on the lower bout of the treble side of the top. Corresponding marks occur on the sides and back. This part of the guitar was probably totally submerged.