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 Tue May 18 18:09:43 2004