"R.W. Behan" wrote in message
news
Greetings, B&W Dinosaurs;

Last night, developing some Ilford HP5 rolls, I mixed some
new working solution of Hypo Clearing Agent. The stock
solution--stored in a cool, dark darkroom--had been mixed
about a year ago, and smelled VERY strongly of ammonia.
How come? Any ideas on the recommended shelf life of this
stuff?

Yes, I mixed a fresh batch, but can anyone explain the
strong odor? What are the decomposition products of
clearing agent? Rich Knoppow?

BTW, it is GREAT to see so many diehards still fussing
with black and white. SILVER HALIDES FOREVER!!

Dick Behan
Lopez Island, WA
Kodak give the shelf life in a filled, sealed, bottle
as three months. Its not long lived because the sulfite,
which is the key ingredient, oxidizes to sulfate with
exposure to the air. Sulfate does not harm but is far less
effective as a wash aid than sulfite.
I am puzzled by the ammonia odor. My guess is that this
is not Kodak Hypo Clearing Agent but something else. There
is no ammonia in the Kodak or Ilford products but there may
be other products based on the old Kodak Hypo Eliminator.
This is a mixture of hydrogen peroxide and ammonia. It
should be avoided for various reasons because the sulfite
wash aids work better. If this is what you have it may have
a very short shelf life. Kodak gives the life of their
mix-it-yourself formula in hours.
I recommend the Kodak product because it has the right
ratio of sulfite to bisulfite and has two sequestering
agents to deal with residue from hardener, where its used,
and with minerals in the water. Ilford's wash aid is a
sulfite wash aid but I have only the information in the MSDS
and can't be sure its buffered. According to the Kodak
research paper and patents the buffering is important.
Another thought, is is possible this was rapid fixer
and not wash aid? That would certainly account for the
ammonia odor. If you mixed Kodak Rapid Selenium Toner in the
wash aid it could also account for the odor. The toner is
mostly ammonium thiosulfate but there wouldn't be much in
the wash aid.


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Richard Knoppow
Los Angeles, CA, USA