Re: Hardening gelatin

sorry - unhardened gelatine :)
Kate
----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Monday, March 29, 2004 5:57 AM
Subject: 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 21:15:42 2004