Martin and Ryuji,
Hmmm....food for thought.
Martin, so our silver developers that contain hydroquinone harden the
cornea? Bummer...is there no safe hardening agent out there? How about
chrome alum?
Ryuji, re: fog, if it completely hardens the gum layer applied then it would
be useless, but if it just hardens a bit of the layer that is in contact
with the paper, then that could just be developed out. That's one thing gum
has going for it--it is not a one shot deal. There are always variables
along the way. The only way I'll be able to find out is when my
hydroquinone order arrives from B and S. But your point about glut
hardening slowly and not instantly is an important one.
Chris
----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
> Although I agree that hydroquinone should be supplied after
> dichromated gelatin is coated to go around rapid reaction between
> them, I don't think immersion is a good idea. Immersed paper would
> contain excess hydroquinone, and unless you remove this, it can cause
> elevated fog with dichromated gum process (and it can completely fog
> silver gelatin process). You could reverse this and coat hydroquinone
> and bathe in dichromate, but that would produce a lot of waste
> chemical containing chromium (bad for environment).
> If you take this approach, my preferred strategy would be to find a
> compatible reducing agent for dichromate, but one that reacts only
> very slowly. This way, you can mix gelatin, water, dichromate and
> reducing agent in one coating solution and coat. Sized paper will be
> hardened by the time it is fully dried.
> My conclusion: glutaraldehyde.
Received on Thu Jul 14 08:41:58 2005
This archive was generated by hypermail 2.1.8 : 08/25/05-05:31:51 PM Z CST