Re: APIS, hydroquinone hardening

----- Original Message -----
From: "Christina Z. Anderson" <zphoto@montana.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, July 14, 2005 4:41 PM
Subject: Re: APIS, hydroquinone hardening

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

I understand that risk occurs when relatively large amounts of Quinol are
involved...

Martin

> 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 10:59:05 2005