Richard J. Kettle (RJKettle@dmaxphoto.com)
Fri, 01 Jan 1999 13:12:07 +0000
I am very interested in any insight into this additive.
I have been mixing large quantities of PMK for use in a Jobo ATL by
a custom B&W lab. They had been getting the PMK from a proprietary
source that was often out of stock, and to alleiviate this problem
asked me to prepare it for them from bulk.
I have been using PMK for sheet film and roll film since 1995 and do
it by hand in trays or stainless drums. The PMK book first edition
suggested a lot of problems with using a JOBO and gave lots of
suggestions for adding inert gases to the drum etc.
When I ran out of my Pyro Gallol I ordered more from another
supplier, due to the fact that my Toronto supplier increased the
price 3x.
This other supplier sent me some EDTA di-sodium to try as an additive
for use with the JOBO. He informed me that some users had told him
that they were getting better results in their JOBO's with the EDTA
and I might consider doing a comparison.
The base formula has been working fine for the B&W Lab so I have been
very hesitant to fix what is not broken.
My research has turned up that EDTA is primarily used as a
sequestering agent for sulphite. In the initial mix there is no need
for a sequestering agent if mixed with distilled water. The working
solution is such a highly diluted mix, it seems inconceivable that it
is needed for the dilution with tap water.
I would be interested in anyones input.
As a side note, I have discovered that there may be a reason for
the disparity in Pyro Gallol pricing. The expensive version is
Reageant grade. The cheaper versions are probably technical grade.
The Reageant grade mixes crystal clear and is very soluble. The
lower grade seems to have some insoluble byproducts in it. I have
mixed a small batch of each that I am going to test side by side and
see if I can determine any difference in the two. The Lab has
suggested to me that they thought the Reageant grade was cleaner and
a little faster. In the near future we hope to try the EDTA as a
test and see if we can discern any difference.
If anyone is interested, I will post results if any.
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