From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 06/12/00-09:16:03 AM Z
Nick Makris wrote:
> ... I found a post that suggests that this test
> doesn't work with the B&S FO. ...
Yea, I commented on that faulty post too.
The Potassium Ferricyanide test does work with B&S powdered FO. I have
been using B&S FO for 14 years and it has always been able to pass the
test. Only one time did I get a failed batch. It was sent on a hot
day, delivered by an UPS truck with no air conditioning in Phoenix.
Since then I shipped by FedEx (air conditioned) during cooler times of
the year and never had a problem. I have some FO powder from a batch
more than ten yesrs old kept as a powder in the freezer, and it still
works perfectly.
> ...In any case, I performed the test and the FO failed. This is very fresh
> stuff from powder that I recently purchased. Two things come to mind here;
> 1) I haven't been totally faithful about not exposing the FO to room light,
> it may have happened once or twice for a short time, and 2) it clears the
> paper unlike a previous batch of B&S FO that had gotten old, (more than 6
> months).
> Has anyone used Potassium Ferricyanide to test B&S FO and what are the
> nuances associated with exposing FO to room light?...
As I have suggested many times, the powdered FO and the mixed solutions
should be stored in the dark, and only opened under a safe light. All
weighing, mixing, coating and processing should be carried out with the
safe light. I use a sodium vapor lamp made for use with g. silver paper
and blue sensitive photographic materials. (For the do-it-yourselfers
and previous posters: This is NOT the type of lamp used in parking
lots.)
I have used incandescent lamps and yellow bug lamps; both of these can
fog a Pt/Pd sensitizer or coating. Before a claim is made by someone
not useing a safe light, they best better do a fogging test including
the pre-exposure threshold. And yes, one may be able to get by with a
little exposure without detectable fogging. Exposure of your sensitizer
is the likely culprit. If not that look into the temperature of storage
or shipping.
And yes, you may even be able to salvage the failed FO powder as I
expect Eric Nielsen may inform us.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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