Down through the various blog posts there is one on nerve glue! Yes nerve glue, glue made from nerves! It is very like hide glue but made from the nerves of the animal rather than the hide or bones. I bought it after a friend of mine, Lucie Tuquoi visited the late great maestro Daniel Friedrich and it was explained to her that when he glued the braces to the soundboard of the guitar he used nerve glue. It was then further explained that the reason he did this was to minimise the top deformation caused by the braces over time. We see this in the best guitars, after a few years we can see undulations in the top where the braces are or rather in-between the braces; according to Friedrich the nerve glue was more elastic and guarded against this happening, I had to try it!
Once I had managed to acquire this rare form of animal glue I used it to glue some small test pieces of spruce but found it very weak, the joints came easily apart and so I put it back on the shelf for another day. More recently I have been researching the subject and came across information that explained how it must be mixed with bone glue before it can be of any use, this explains a lot, so I made up a batch of bone and nerve glue and began using it when gluing the braces to the next tops and backs. I certainly notice a difference and will monitor the results. Here are some photos so far.
Bone and nerve glue, the bone glue is in pearl form and the nerve is powder.
The glue being heated in the bain marie with a willow stick to stir it, the willow stick is used because it contains salicylic acid which inhibits the growth of mould.