[pure-silver] Re: Selenium toning question, was stopbath kills fixer
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 26 Jan 2005 21:01:20 -0800
----- Original Message -----
From: <anclancy@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, January 26, 2005 8:39 PM
Subject: [pure-silver] Re: Selenium toning question, was
stopbath kills fixer
> there is no need to just tone 4 11x14 and toss. it is not
> good for the environment, and the selenium is still good.
> as it begins to slow down, just add some selenium to the
> mixture and continue to use.
>
> I haven't read the directions in a long time, so i can't
> comment of the number of prints per ounce, but as many
> others, i continue to use the toner, adding as needed. The
> last time i topped off a 1:10 ratio was last year some
> time, and i tone frequently. Don't remember the last time
> the other ratios have had to had additional selenium
> added.
>
> The directions also, indicate that one can mix the
> selenium with HCA, which is no longer considered a wise
> and necessary directions.
>
>
> regards,
> ann
The capacity of KRST depends on the material being toned
and on the nature of the images. Low key images take up more
selenium from the toner so the capacity is less than for
high key. The capicity is pretty much judged by the length
of time it takes the toner to work. If it gets too slow add
more concentrate as you recommend.
The use of Kodak Hypo Clearing Agent as a diluent was
suggested by Kodak only when the toner was highly diluted,
say 1:20, as was previously recommended for image
protection. The reason is that the bath then acted as a
combination of toner and wash aid. KRST at 1:20 seems no
longer to be a good protectant although the slight
intensifying action may be desirable for its own sake. At
this dilution the capacity of both toner and wash aid is
similar. For stronger dilutions its recommended that the
tone be diluted in plain water and the wash aid used
separately first. The reason is to avoid the possibility of
staining due to precipitation of elemental Selenium on the
print due to its being acid. I doubt if this is a serious
problem for prints or film that has been washed. Since KRST
contains a fairly large amount of Ammonium thiosulfate
prints can be toned directly from the toner, the hypo does
not affect the toner. Its possible that the acid might
result in staining from the above reason but I am uncertain
if this happens.
Note that Kodak at one time recommended KRST diluted 1:9
as a test for residual silver halide in place of the older
Sodium sulfide test. This test works on well washed material
but fails if there is an excess of hypo. I have never seen
an explanation of the chemistry behind this. As a test for
completeness of fixing KRST has the advantage over Sulfide
of being odor free and being more stable in storage.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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