January 30, 2006, from Lloyd Erlick,

I've wrestled with this problem for some
time. I use my KRST diluted only 1+5, so it's
quite costly. I also tend to mix up three
liters at a time -- (well, I don't actually
mix it up any more, I simply continuously top
up my stock, but that's another story...) --
so that makes it even more expensive.

Some time ago I went on an anti-smell rampage
in my darkroom practice. I just had had
enough of any smell I didn't like, and I
looked for ways to eliminate them. I found
the number one culprit in the darkroom is
acid. Acid stop bath, acid in fixer, the lot.
I removed all forms of acid from my darkroom
and found the place was far more pleasant. I
also found my materials behaved better.

For complete details about smell abatement in
the darkroom, see my article under the
'technical' button in the table of contents
of my website, heylloyd.com.

Regarding selenium toner (KRST), I found that
the dark murkiness it inevitably developed
over time and use failed to appear once there
was no acid in my chemistry. The faint traces
of the dark precipitate that did appear were
easy to remove by regular filtering through
coffee filters. My KRST performed perfectly
well for years while remaining close to
water-clear. It depletes through solution
carry-out on the sheets of FB paper I tone.
Carry-out depletes the solution far more
quickly than chemical exhaustion because of
toning action. I continuously to up my
solution with fresh KRST as needed to retain
the solution level I desire.

I've never heard any report of how to keep
selenium toner from becoming dark and murky.
I can't explain how the absence of acid
contributes, or perhaps more properly, how
acid causes the dark murk. But I do know it
works.

(Please note that changing stop bath to
citric acid is fine for smell abatement, but
it still murks up the selenium toner. If an
acid stop is used but the fixer is non-acid,
it is still not possible to adequately wash
the acid from the FB material; the KRST will
still murk up, although it will take longer.
Water-stop and non-acid fixer contribute to
clear KRST long-term.)

Also, I think it's necessary to make KRST
with distilled water.

My web site also has an article about my use
of KRST.

regards,
--le