At 04:15 PM 7/29/2010 , you wrote:
...
...
Selenium toner can cause staining from preciptated
elemental
selenium if the emulsion is sufficiently acid a bath in a
mildly akaline or neutral bath should suffice to prepare
it
for toning. If a sulfite wash aid is used that should do
it
even when an acid stop bath and fixer have been used.
...
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
===================
July 30, 2010, from Lloyd Erlick,
I'm very familiar with the yellow staining you're
referring to. To my color
perception it is extremely hard to see against a white or
near white
background, but much clearer if it lands on black areas.
Some people see it
as orange, I'm told.
Part of my reason for all the poking around I had to do
with selenium toner
was that occasionally I would fail to see a yellow stain.
I need a way to
be sure they do not form at all.
The precipitation I'm talking about is the black or dark
brown stuff that
gets thrown in the selenium toner storage container, or in
the toner tray
if it's there long enough.
Since I use an expensively high concentration of selenium
toner, I want to
keep my working solution in good condition. Until I gave
up acid I never
could beat that problem. When I started playing around
trying to stop the
odors I did not like in my darkroom, I found that reducing
the acid in my
line had an unexpected (by me, at least) positive effect
on my selenium
toner. But compared to not using acid at all, just
attempting to rinse away
whatever acid I did use was of only partial utility. I
suppose eventually
all acid can be washed out of a sheet of paper, but I
doubt it will occur
during my lifetime.
My processing sequence does not require any step between
fixer and selenium
toner. There is no acid to carry over, hence none to
neutralize or rinse
away. Carry over from my plain fixer includes only sodium
thiosulfate and
sodium sulfite (the only ingredients in plain fixer),
neither of which is
deleterious to selenium toner (which the manufacturer
packages with quite a
bit of ammonium thiosulfate to start with).
For a certain period I did use a processing step between
(acid) fixer and
selenium toner. I soaked it in KHCA (hypo clearing agent),
as Richard
suggests, and it did work as far as stains on the print
were concerned.
I've found that sulfur dioxide can rear its ugly scent
unexpectedly if
there is any acid at all in my process. Same for hydrogen
sulfide. Maybe
not in great quantity - it's probably fair to say bad
smells are a thing of
mine... (but I doubt I'm the only one...)
For a normal, plain vanilla darkroom for black and white
materials, I think
it is possible to say that noxious gases and smells such
as sulfur dioxide
and hydrogen sulfide can be absolutely eliminated, by
which I mean reduced
to zero. Chemical exposure of our bodies in our darkrooms
can be reduced to zero if we wear gloves or otherwise work
out a method of
getting nothing on our skin (which as we all know is far
from difficult).
Nothing on our skin, nothing to breathe, that leaves
drinking and eating
our chemicals, yum!
regards,
--le
