Larry Toto was quoting some fellow who called hot hide glue "garbage." 
In some cases, I will have to agree in a limited way.  I have certainly
run into some of that.

Hobbyists who want to restore their own player pianos should definitely
use hot hide glue, of course, but more than one has ordered a pound of
Schaff's hide glue crystals, and frankly, I don't see how anyone can use
it. (Buy it from Player Piano Co.)

Schaff may have, by now, a different grade, I can't say. I buy the glue
by 100 lb. lots, as does any serious woodworker or professional restorer
who appreciates the difference between hot hide glue and, say, Titebond.
Between the two, or Weldwood, or anything else for that matter, hot hide 
glue is stronger, easier to use, far and away more versatile, and
everything else you want in a glue all wrapped up in one simple product. 
It can be even made waterproof! [see  Orchestrion Builder's Manual and
Pneumatics Handbook for more details]. But as you go up in gram strength,
the characteristics of your glue changes drastically, until it does not
work anymore under normal shop conditions and temperatures. The stronger 
the glue, the less and less latitude it offers you. It sets almost
instantly, will not wet its surfaces, and will not brush on anything or
flow out evenly. It congeals almost as soon as it touches a brush. That
means, it must be used in a totally different manner than from a common
glue pot to room temperature work.

When I received some of this grade of glue from an MMD subscriber
recently, I hadn't realized before why some people had such trouble
using it. Now, I realize that most just quietly wonder how anybody
could use such a product, and quietly stick with Titebond. Well, the
problem isn't with you! It's with merchants who don't know enough about
it to place an order with the manufacturer, and, a manufacturer who
isn't conscientious enough to tell them what they should be buying
instead, letting them make a mistake that will turn everybody off of
hide glue.

If you happen to have some of this stuff and don't want to just throw
it away, you can add some potassium chloride (salt substitute) or
so-called potash, which is the common industry term for potassium salts,
either a carbonate, a hydroxide, a sulfate, a chloride, or whatever
combination that may find itself in their bag and gets labeled potash.
It's very cheap, but you don't want a 50 lb bag of it, so try some salt
substitute from the grocery store, or even some urea fertilizer will
work in smaller amounts.  Add about 3 tbl/qt of the KCl and try that
first before throwing out the entire bag of glue. Or, after you buy some
workable grade of hide glue, preferably in the 150 gram strength
category, you can add the other to it, in a ration of, say, 4 to one,
and gradually get rid of it that way.  Remember, if it isn't fun and
rewarding to use, something's wrong, and it may not be you.

One last comment might also be in order, here. There are innumerable
qualities and properties of hot hide crystals. Generally, the weaker
the glue, the wider latitude of compatibility to materials it will have.
The less gellatinous it becomes when cold-soaked in water overnight,
and sets much slower, too. 130-160 gram strength (taken strictly from
viscosity measurements) will be found to be optimum in our work, but
should never be heated over 150 degrees farenheit, or it breaks down
quickly in the pot.  140-145 is about right. Once your pot has been
adjusted for this temperature with an air jacket, it is best to just
leave it on and keep the container covered. Use a glass Vlassic pickle
jar and plastic lids, like you find covering little plastic single-
serving yogurt cups. When in use, dump in some smooth Styrofoam
packaging pellets to prevent evaporation and to support your brush from
dropping into the jar. And of course, potassium salts also help this
glue, and extend its ability to flow, slow its setting time, and
strengthen its final bond a little by elasticizing the glue just a bit.

Craig Brougher