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feb2605 from Lloyd Erlick,

I've got an article on my website about selenium toner.
Look under the 'technical' heading in the table of
contents. I keep meaning to add to this article, in
light of what I've observed regarding the length of
time I can keep my --and yours too, I see -- jug of
KRST working soilution.

In my opinion, a diluted working solution of selenium
toner (I use KRST) can be stored for years. I'm tempted
to say indefinitely. I'm not so sure this applies to
greater dilutions, like 1+20 or 1+43. I work with KRST
diluted 1+5, and my working solution is several years
old, with a couple of lengthy periods of idleness
included. I think an actively used solution should last
indefinitely because it will be depleted much more
rapidly by solution carry-out on the sheets than by any
other factor. I continually replenish mine by topping
up to my usual volume with fresh KRST diluted 1+5.

The black material seems to be quite inherent to KRST.
I've seen tiny piles of wee crystals of it in the
bottom of unopened one gallon jugs of KRST concentrate.
I think it's something that will come out of solution
over time. I am presuming it is the same stuff as you
see in your container. And I am also presuming (not a
chemist!) that it is the dark material that
precipitates in my working solution, eventually murking
it up so much I hate to use it. It also adheres
tenaciously to the walls of my storage jug.

I've found a nearly complete solution to the black
precipitate in KRST. It's an unexpected (by me, anyway)
side bonus to eliminating acids from my darkroom in
order to abate smell production.

When no acid is carried into my KRST working solution,
I notice vastly less black precipitate. I can keep my
working solution almost water-clear by using paper
coffee filters to remove what little black stuff forms.

At first I reduced darkroom smell by changing from
acetic to citric acid stop baths. Soon my fixer
experiments led me to the path of least resistance:
Plain Fixer, as Ansel Adams calls it. (It's not
'plain'; it has sodium sulfite as well as sodium
thiosulfate.) Once the fixer had no acid, so the only
acid present was from the rinsed (there is no perfect
rinse!) print coming from the stop, I noticed a decline
in the black stuff in the KRST. After I replaced the
acid stop with plain water rinses (four; I know, it's
extreme. Extremely easy and cheap) the black stuff
nearly stopped. I filter my solution through a paper
coffee filter about once per darkroom session.
Sometimes I filter it both before and after I use it.
Stored in a container that permits examination of the
contents, it's easy to judge when to filter.

I love glass containers, and I'm sure it's the best for
storage of selenium toner. But sooner or later it gets
dropped ... I'd say if one uses glass, it should live
in the sink and never go out of the sink. Personally, I
use plastic.

regards,
--le

Everything I have read (and experienced) with this toner is that its life is
dependent upon the number of times the solution is used to tone not how long
it is sitting in  the bottle.  The tip off that it is losing its strength is
when the toning times get intolerably long.  I keep my diluted solution in a
heavy plastic bottle I salvaged from some other product.  When I get that
ocasional black stuff and it gets too bothersome I either slowly pour off
the solution from the bottle into the tray and rinse out the small amt left
in the bottle or pour the entire solution through a piece of coffee filter
paper.

Sam
.