Whoever did Fishandfowlers repair on his L.C. Smith knew that the most important part of an invisible repair job is the fitting. If they had done a bit better at color match, he might have never noticed the repair. At first, I thought it might be a natural division between sapwood and darker wood.
The most invisible glue joints I've managed in walnut were with Titebond II wood glue, Titebond Polyurethane glue, thin boat builders type 4:1 epoxy, Acraglas epoxy, and regular clear Duco syringe type 60 min. epoxy, in that order. The differences in visibility were small, and close fitting of the joint, and color and grain match of the walnut are more important. The epoxies and polyurethane seems to be stronger if there is any trace of oil left in the wood. Glue-up soon after solvent de-oiling is important because any oil deep in the wood will continue to leach toward the surface. The polyurethane is hardest to work with because of the sticky foam-out at the joint while clamping. Also, this foam-out is the hardest to clean up afterward as it will stain the surrounding wood more than other glues affecting penetration of stains or stock finishes. Perhaps a clean up right after clamping with urethane thinner would help as Bill Schodlatz notes about cleaning epoxy squeeze out with alcohol.
