[Frameworks] B+W Handprocessing Reversal Bleach?

edwin m ed___209 at hotmail.com
Tue Oct 4 14:36:20 CDT 2011



i don't think there's an off-the-shelf solution without potassium dichromate or permanganate. foma kits use dichromate and ilford uses permanganate. out of those two, permanganate is considered the safer. 

it's also worth saying that potassium ferricyanide might not be any less toxic (its use is linked to cyanide poisoning). if you do use it, apparently 10g in 500ml water will do for the bleach, and then 100g sodium sulphite in 500ml water for the clearing bath. don't let acid anywhere near, or it'll give off a lot of cyanide gas

hope some of that's useful

edwin



> Date: Tue, 4 Oct 2011 14:47:26 -0300
> From: marcia.l.connolly at gmail.com
> To: frameworks at jonasmekasfilms.com
> Subject: [Frameworks] B+W Handprocessing Reversal Bleach?
> 
> Hello all I'm teaching Experimental Film at NSCAD and we are
> hand-processing in a communal darkroom and there is a concern about
> our bleach. Does anyone know what the least toxic recipe for a 3374
> Hicon B+W  reversal bleach is? One that does not use P. Dichromate or
> Permanganate?
> 
> Has anyone tried a Potassium Ferricynide based bleach?
> 
> Any help would be appreciated.
> 
> Marcia Connolly
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