From: Andre Fuhrmann (andre.fuhrmann@uni-konstanz.de)
Date: 01/27/02-12:17:03 PM Z
>... my first throught is that if the fixer doesn't
>bleach how do we know the toner tones? But more to the point, this is the
>first I ever heard of just selenium bleaching -- in fact it's an
>intensifier (after fixing, with KRS). I used the T-55 & T-56 quite a
>bit... never noticed any bleaching. Did you see that happen? Are you
>sure it was the selenium?
I think you are right, Judy, just selenium cannot bleach the image.
(Sorry for wrongly raising this as a possibility in my earlier
posting.) But can pure selenium tone? All selenium toners known to
me are basically this: Sodiumselenosulfite (don't know whether this
is the correct English term, the formula is Na2SSeO3). Toning
proceeds by binding the silver electrons of the image to the selenium
so dissolved, thus producing Ag2S in the image and releasing Na2SO3,
i.e. sodium sulfite. The latter is known from developers as the
stuff that prevents oxidisation but also has a moderate capacity to
dissolve silver -- not as strongly as hypo but it does have that
effect. As the toning process progresses, the concentration of
sodium sulfite in the solution increases. I find it hard to believe
that this is a dirty trick that Kodak and others play to make ALT
processes harder. Question to our resident chemists: is there a
practicable way of producing solutions of selenium fit for toning
such that the solving agent would not also dissolve silver to some
degree?
André
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