June 2005 Alt-Photo-Process-L: Re: GENTLE BLEACH

From: MARTINM ^lt;martinm@SoftHome.net>
Date: 06/03/05-10:42:32 PM Z
Message-id: <004601c568bf$eabaf390$b19f4854@MUMBOSATO>

----- Original Message -----
From: "Liam Lawless" <liam.lawless@blueyonder.co.uk>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, June 03, 2005 1:15 AM
Subject: RE: GENTLE BLEACH

> For reversal, you need a non-halogenising bleach that dissolves metallic
> silver WITHOUT altering silver halide, and I'm not aware of many suitable
> bleaches. Mike Ware suggested a bleach based on cerium nitrate, but I
found
> it extrememly slow. It's also a great deal more expensive than
permanganate
> and dichromate.

> Liam

It might be possible to form a reversal bleach based on ferric nitrate (or
ferric sulfate) + potassium persulfate. At least for ultra-fine silver
grains it works nicely:

Ferric nitrate (or ferric sulfate).....100g
potassium persulfate.....................20g
water.............................................1L

Martin
Received on Fri Jun 3 22:41:04 2005