Re: APIS, hydroquinone hardening

From: Christina Z. Anderson ^lt;[email protected]>
Date: 07/14/05-08:41:38 AM Z
Message-id: <001001c58882$26bb43e0$676992d8@oemcomputer>

Martin and Ryuji, for thought.

Martin, so our silver developers that contain hydroquinone harden the
cornea? 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.

----- Original Message -----
From: "Ryuji Suzuki" <>
> 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

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