Dick Merchant wondered if cold liquid hide glue is just as good as hot
hide glue.

I don't use liquid hide glue at all, but there are a few simple
principles that you or anyone can apply to answer your questions about
any glue and how you might expect it to act.

First of all, I ask myself, what physical principle causes the glue to
set, initially?  If it is a combination of things, like both water
content and temperature, or a new space age chemical reaction within
itself or with the wood, then you can be sure that the applied "pool"
of liquid glue you began with is going to gel or set that way too, and
from there on, it is going to start the shrinking process, getting very
tight immediately.

But if this glue dries only by losing moisture, like PVAs, then the
only advantage of using liquid hide glue is going to be that you can
take things apart again, which is good, but you have lost your main
advantage for player pianos, that being an airtight joint that holds
a good vacuum.

You might be able to tell more from the label regarding its setting
time, and the clamping or weighting required.  Basically you can make
liquid hide glue by adding acetic acid (ideally odorless, from photo-
graphic supply houses), and that it works well when replacing an old
joint that you have broken apart, when making a house call or some-
thing. I can't answer for the ready-made stuff by Titebond with all
the other chemicals in it. I don't know what they are for.

So there is one sure way to find out, isn't there?  Cut some softwood
lathe into 5" long pieces and glue about 10 of them over supply holes
in an airtight board with a supply nipple in its end. When fully dry,
put the system on a bubble jar with regulated vacuum supply and just
compare the activity in the jar with the supply board when you had tape
over the same holes. If you see any difference at all, the glue leaks.
With hot hide glue, you will see no difference at all.

Craig Brougher