February 4, 2006
Some observations of the behaviour of Kodak
Rapid Selenium Toner (KRST) over a long time
including periods of use and periods of
disuse.

Recently I made some prints for the first
time in too long. I've been keeping records
on my present jug of selenium toner (KRST),
which I first mixed in 2001.

It's diluted 1+5 in distilled water. I
normally keep around 3000 ml in the jug, but
the level was quite low. I had not used it
since early 2003, and apparently I did not
top it up before I put it in storage.

Examination of the contents of the jug of
KRST showed it was quite clear, no trace of
the characteristic murkiness that often
darkens KRST. Also, a large amount of white
fungus was living in it -- sort of like a
miniature aurora borealis hanging in space
within the solution. It seemed to hold
together like a jelly fish. I poured it
through a coffee filter, scrubbed out the
jug, and filtered it through a fresh coffee
filter back into the jug. It smelled fairly
prominently of ammonia. I expect future
regular and frequent filtering will keep the
fungus from proliferating again.

The first print I made was toned in the KRST
before I added a liter of fresh mix to top it
up. It toned as it had always done. I
couldn't see any change in the action of the
solution.

The second print was made after I added 200
ml KRST concentrate plus 1000 ml distilled
water to top up the jug. The toning action
was as usual. The smell of ammonia was quite
strong.

So it seems to me a solution of KRST can last
pretty much as long as one wants. As long as
I'm active in the darkroom I don't see why I
can't have this very jug or its descendents
at work. Really, as a darkroom effluent, KRST
need only dribble out in drainings from each
sheet toned, not as a dumped container of
solution.

The solution now has  toned the equivalent of
1098 8x10 sheets of FB material.

I attribute the lack of precipitate in the
used KRST to the absence of acid in my
darkroom.

regards,
--le