Yes, cold hide glue begins as hot hide glue, and then you make it dry
slower.  We cannot speak for Franklin "Titebond" or other patented glue
manufacturers, but when we have a special need for slow drying hot glue
we make our own.

When we install or reinstall a soundboard, which requires massive
amounts of glue to be spread and then a preponderance of clamps
applied, we mix up a special bottle of hide glue with the addition of
thio urea to it.  I don't have any recipe, I just add enough, dissolved
in water, to slow hardening as much as I want.

The old guys also said if you couldn't find any such chemical additive,
then just piss into it.  I'm not kidding -- urine will cause the same
effect.

Isn't it just amazing what knowledge gets lost through the ages?

D. L. Bullock    Piano World    St. Louis