[pure-silver] Re: Paraformaldehyde/Acetone in lith developers
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Tue, 2 Mar 2010 12:16:16 -0800
----- Original Message -----
From: "Robert Hall" <robert.g.hall@xxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Tuesday, March 02, 2010 11:49 AM
Subject: [pure-silver] Re: Paraformaldehyde/Acetone in lith
developers
I'll be your Huckleberry...
"Note that he states that metaborate is inferior to borax
as a buffer."
Why would I want to know this?
R
At one time Kodak was pushing Kodalk formulas because of
the buffering ability of Kodalk. Evidently it was never
true. This included a Kodalk version of D-76. In fact, its
possible the packaged version of D-76 may have been the
Kodalk version for a time (a long time ago). D-76 needs a
buffer because of a slow interaction between hydroquinone
and sulfite which produces sodium hydroxide. There is enough
hydroxide generated to increase the activity of D-76 slowly
with time. The solution to this worked out at Kodak in 1929
was to use a buffer mixture of borax and boric acid in place
of the borax alone. Current packaged D-76 is evidently (from
the MSDS) this version. Apparently someone at Kodak thought
that switching from borax to Kodalk would have the same
buffering effect; it didn't.
I also have some question about the use of borates in
pyro developers. Some older literature states that they are
not compatible although I've forgotten the reason given.
I've also read why Kodalk is OK in PMK although I again
can't remember the reason or the source.
I wonder how many have tried the old ABC pyro developer
or Kodak's variation on it D-7 a pyro and metol developer.
The metol acts as a preservative for the pyro extending its
life. Both of these developers generate a stain image.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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