George writes:

> So far all I've been able to do with these "late-model" (1926)
> Gulbransen Unit-Pnematics is DESTROY THEM!  The fixed board is very
> thin, maybe 3/16", and the old hide glue is incredible.
>  Should I cook them longer? steam them? (Reblitz doesn't like
> moisture.)

A previous post suggested freezing the entire assembly as cold as you
can find, preferably below zero.  The hide glue become quite brittle,
(along with everything else except the wood) and shatters quite
nicely.  Removing a pin block from an old upright taught me about the
effects of hot vinegar and water on glue joints.   I also added alcohol
just before pouring the mixture on the glue joints but I got a feeling
the alcohol simply vaporized with the heat and so did nothing to induce
penetration.  The hotter the mix the better it penetrates and being
that it has vinegar, it should get hotter than 212 deg F (100 C) and
really do a good job on softening the old glue.  If you apply the mix
from a squeeze bottle or eye dropper, or I believe it's called a
pipette, the amount shouldn't amount to so much that damage occurs.
I've been steaming pneumatics in a covered kettle for years now, and
the minor warpage that occurs eventually flattens back out again by the
time I reglue the pneumatics back on.  The tier that the assembly is
glued to will get some moisture on it as well, but once again should
only be minor and being that it is much heftier in size and mass, it
shouldn't warp at all.  Allow everything to dry completely and recoat
with shellac a few times to reseal the wood.  Then recover and reglue.
I've been regluing with PVC-E glue for the last couple of years, but
some people like to stick with original materials as much as possible
so they use hide glue.

There was quite a thread on Gulbransen's a while back.  They can be
quite a charming bit of work to rebuild.  I hope it works well for you
when you're finished.  Good luck.

Lar