Re: Hardening gelatin

While thinking about my experiment in hardening gum, I got to wondering
how people who harden gelatin for sizing actually know that hardening
has taken place.

What I'm hardening is watercolor paint with gum added to it, the same
gum/pigment mix that I use for gum printing. Dried unhardened gum is
very soluble in water; that's one of the basic principles that underly
the gum process, after all, and the added color makes it very easy to
tell whether the gum has been hardened: just drop a drop of water onto
the dried gum/paint and blot. If I get a round white spot where the drop
of water dissolved the gum back to white paper, I can be sure that
hardening didn't take place.

But when you're hardening gelatin, how do you know? Since, like Judy,
I've long questioned the wisdom of assuming that the chemistry of gum
and the chemistry of gelatin are interchangeable, it occurred to me that
this might be one place where I could compare the two in some kind of
quasi-systematic way, since I have these hardening agents that are
usually used for gelatin, that I'm using to harden gum with. If gelatin
and gum behave similarly in this case, then I would have to consider
softening my resistance to the idea that gum chemistry = gelatin
chemistry.

 But right away I'm up against this question: if I do this comparison,
how will I know that the gelatin is hardened? In my experience dried
gelatin isn't as hypersoluble in water as gum is; I doubt that dropping
a drop of cold water onto unhardened dried gelatin would dissolve it
instantly in the same way that a drop of water dissolves unhardened
dried gum; it would have to be hot water for that to happen, yes? If the
hardening can't even be judged under the same conditions, how could it
be argued that the two things are functionally the same?
kt
Received on Thu Mar 18 12:50:38 2004