John Ruth wrote: "And, contrary to advertising claims, Old Brown Glue is
not hot hide glue" 

Correct, John.  Both Franklin and Old Brown Glue are buhl work glues,
designed to hold disparate materials to wood.  Buhl work glues retain
enough plasticity to keep stone, metal, bone and shell from popping out
from the expansion and contraction of wood.  These two add urea (that's
urine) to hide glue, in the English tradition.  The French added garlic
oil.  Think twice about licking your fingers...  But they will, as
designed, hold metal to wood. 

I grew up with hot hide glue.  My grandfather built custom picture
frames and hot glue is what we used.  Initially, my job was to go into
the shop and prepare the glue, heating it, adding a bit of water and/or
glue beads to the electric glue pot.  Get it ready for him to use. 
Maybe that's why I don't find it inconvenient.  Some add a bit of salt
to the mixture, though I never have.  Now I have a couple of double
boiler glue pots, one copper, the other an old cast iron pot. 

Both forms are reversible.  Both adhere to previous hide glues as well,
which is a real advantage in repairs to old furniture. 

Mike in Woodland