Re: Tanning theory of dichromated colloids (was gelatin

"I wonder what the difference is. At any rate, this makes me even less
confident that the holography literature is a useful place for me to look
for answers about gum printing."

I cannot judge about the utility of that literature for gum printing but
assume that the
basic principles of light-induced crosslinking remain the same in both
cases. Beside different exposure levels (generally at different wavelengths)
the main difference may be in the particular substrate for the colloid:
making stick a layer of gelatin, PVA, gum etc. on a transparent glass or
plastic substrate can be a challenge.

Martin

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, May 18, 2004 7:13 PM
Subject: Re: Tanning theory of dichromated colloids (was gelatin

> MARTINM wrote:
> >
> > "I was thinking of adding monomers to the colloid. I expect this to
enhance
> > both speed and rigidity of the colloid. E.g. it actually might "replace"
the
> > pre-hardening step - hence the handling of formaldehyde and the like."
> >
> > Sorry, I thought your former "encounter" with glutaraldehyde was related
to
> > gum printing.
>
> No, the reason I ordered the glutaraldehyde was because I wanted to
> paint (make paintings) using the gum-pigment mixes that I use for gum
> printing. Since dried unhardened gum is totally soluble, I needed a way
> to harden the gum. Now I'm afraid of the stuff and will never use it for
> that purpose, but glyoxal works quite well. People do use these gelatin
> hardeners to harden the size when they use gelatin to size paper for gum
> printing, but the size is an optional step in paper preparation, not
> part of the process per se. I can see how it would be confusing.
>
>
> >
> > "You just put dichromate with gum and go, that's all there is to it."
> >
> > I see. So you are likely to be dealing with much higher levels of
> > crosslinking.
> > For holography dichromated gum, PVA etc. absolutely requires some sort
of
> > pre-hardening.
> >
>
> Hmm. I wonder what the difference is. At any rate, this makes me even
> less confident that the holography literature is a useful place for me
> to look for answers about gum printing.
>
> Katharine
Received on Wed May 19 05:52:12 2004