Re: Hardening gelatin

Hi Kate,
Just want to make sure I understand you; are you saying here that before
you started using hardened gelatin for sizing for gum printing, you used
unhardened gum for sizing? Or did you mean to say unhardened gelatin?
Thanks,
Katharine

Kate Mahoney wrote:
 When using hardener for gelatine sizing for
> gum, I don't need to recoat between layers nearly as much, as I did when
> using unhardened gum. I found that if I didn't recoat between layers before,
> I would always end up with staining sooner or later.
>
> Kate
> ----- Original Message -----
> From: "Katharine Thayer" <kthayer@pacifier.com>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Thursday, March 18, 2004 11:16 PM
> Subject: 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 Sun Mar 28 19:53:30 2004