Opinions run strong among musical instrument builder regarding glue. It is a really hot topic. So much relies on the ability of glue to hold things together (and to come apart easily for repairs). At Bear Meadow, we have joined the march back into time, to adopt the oldest known adhesive, hide glue.
I have recently entered the fray of this argument by adopting Liquid Fish Glue. Made from the skin of cold-water fish, LFG has none of the liabilites of hide glue, all of its virtues and these virtues unique to it:
I now use LFG for all major assembly. It seems to be just as strong as hide glue, and had the added advantage that it's open time is about 30 minutes. That is plenty of time to get the primary assembly of back, sides, tailblock and peghead. I've found that joints are much more reliable since I switched to fish glue.
I still use hide glue, especially where it is handy to have the hot liquid re-opening an adjacent joint, such as in laying in inlay purfling.
There is some concern in the lutherie community that fish glue may deteriorate. Hot hide glue joints exist from antiquity, and are still quite sound. The major supplier of Liquid Fish Glue, Richard Norland, of Norland Products, states, "We've run lon-term stability tests on Dried Fish Gelatin and even after 10 years, there were no changes in pH, bacteria or viscosity when re-dissolved. Our customers have been very satisfied with the durability of our Fish Glue".
Hot hide glue still has its uses, along with aliphatic resins, epoxies and cyano-acrylic glues. Even Gorilla glue, sometimes!
Hide glue is made from the flesh of animals, and is a complex mixture of proteins. It is very strong, and quite versatile. If you want to know about hide glue, visit the Hide Glue FAQ.
We use hide glue for all major glue jobs. Here and there, epoxy, aliphatic resin ("yellow glue") and cyanoacryllic ("crazy glue") is also used for special purposes. There is no one glue for all purposes, but if there were, hide glue would be it.
For instance, we attach the top of the dulcimer with a specially weakened formulation of hide glue. If a sharp jar hits the instrument, we want the top to pop off (undamaged) rather than cling mightily to the body of the dulcimer and get smashed. Using a weak preparation also makes it easier to get the top off for repairs inside. Only Bear Meadow instruments are repairable in this manner. Other makers follow guitar practice and permanently glue on the top (without furnishing a soundhole big enough to get a hand and tools through).
The set-up we use for using hide glue is very simple: