Re: Less hazardous silver bleaches


Kevin O'Brien (kob@paradise.net.nz)
Sun, 14 Feb 1999 21:02:06 +1300


From: Sandy King <sanking@hubcap.clemson.edu>
>What is the primary use of these formulas, 1) contrast control via
>bleaching and redevlopment, or 2) bleaching for reversal processing?

Sandy,
Those bleaches are for (2) removing silver for reversal processing. Once the
sulphuric has converted the silver it gets washed out.

For re-developing or toning (1) the silver needs to remain in a useable
form. The bleaches with hydrochloric acid do that as do others containing
(plain) salt.
This is one from Ilford, given for stain removal, but appears generally
useful as well as safe:
    Pot permanganate 6g
    Common salt 13g
    Acetic acid, glacial 50ml
    Water to 1l

This can be thought of as:
    Strong white vinegar 1 litrel
    Salt 1tb
    Pot permanganate (Condys crystals) 1tp

Negs or prints left in soln with continuous rocking for abt twice as long as
required to bleach image. Wash until water no longer pink. Soak in 5%
metabusulphite soln until no brown permanganate stain remains. The image can
then be re-developed in a low sulphite developer or otherwise toned.

I have not tried it. I appeals because it can be made up very safely, if the
glacial acetic acid is avoided by using the pre-diluted supermarket vinegar.
It should be handy for sulphur toning processes.

I would be pleased to hear how it works from anyone who may care to try it.
It would be useful to build up a collection of modern, safe, formulations.

Kevin O'Brien



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