Digital BW, The Print

On 21/09/2010 Clayton Price wrote:
> I believe you are mistaken about sodium sulfate being the ingredient
> that removed some of the silver, since it's found in both the 
> developers
> and fixers

Silver sulphite (not sulphate, unused in B&W AFAICR) is a silver solvent 
especially used in fine-grain developers to restrain grain clumping. 
Potassium bromide is a restrainer, used to restrain fog arising through 
dev of unexposed silver.

Used together in the correct balance they have a complementary action, 
with bromide allowing development to proceed further (realising better 
speed/sensitivity from the material) without undue fog, and sulphite 
restraining graininess by dissolving some of the image silver as it is 
formed by dev. Add local exhaustion of diluted dev in developed areas and 
you got compensation (progessive compression of highlights, in negs) and 
also adjacency effects that enhanced apparent sharpness.

I quite often added both to HC110 to soften its rather gritty grain.

Sulphite + KBr in print devs was a good part of the reason for the nasty 
olive green tinge and mediocre DMax that many papers produced after 
environmental concerns and the Bunker Hunt swindle reduced silver content.

Sulphite will attack image silver with a bleaching action, if given long 
enough. You're correct its presence in fixer was to maintain acidity, but 
it also meant fixing had to be as brief as was necessary to clear 
undeveloped halide, before it started munching away at print highlights.

Now back to the dratted SATA problems I'm having, which are not so much fun...
-- 
Regards

Tony Sleep
http://tonysleep.co.uk