Hide Glue

Hide glue is probably one of the best glues available.  It was "replaced" years ago by modern glues because of their ease of use and ability to withstand water.  Hide glue has several distinct advantages to it.  It is extremely strong, it is very hard when dry (it transmits sound vibrations without dampening them), it can be released with heat and water (you can make repairs easily) and joints secured with it have little "creep" to them (they don't move while gluing up).    Here is how I mix up a pot of glue.

This is what the glue crystals look like when dry.

 I mix one part dry glue with two parts water.

 After about an hour the crystals have absorbed the water and they look like "fish eggs."

 Next the glue slurry goes into the "glue pot" where it is heated between 140 and 150 degrees.

 After about an hour in the pot it looks like this, a clear amber liquid.

Leave sit over night and it will be a clear solid, ready for reheating and use for several weeks.  The glue sets very quickly so you have to either work fast or heat the pieces to be glued to increase the glue's open time.  Great stuff!