[pure-silver] Re: 'Ripening' procedure for developer?
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sat, 5 May 2007 12:02:06 -0700
----- Original Message -----
From: "mail1" <mail1@xxxxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, May 05, 2007 10:45 AM
Subject: [pure-silver] Re: 'Ripening' procedure for
developer?
Do you mean 24 grams to 4 liters of H2O for an 8%
solution?
A 2% solution will also work.
Also you might consider leaving out the Hydroquinone and
increasing the
Metol to 5 to 7.5 Grams. In Metol Hydroquinone developers
of low alkalinity
most of the silver reduction is accomplished by Metol, as
the Hydroquinone
is a weakly ionized and almost inactive under these
conditions, the increase
of Metol makes up for the Hydroquinone. Aeration of Metol
Hydroquinone
developers, pH 8.4 to 8.8 causes an increase in activity,
but low alkalinity
Metol developers show almost no change in activity. You
also can reduce
Sodium Sulfite from 100 grams/liter to 75 or 50 grams to
improve acutance.
Jonathan Ayers [mail1@xxxxxxxxxxxxxxxxx]
In the 1929 paper describing buffered D-76 the authors
show the results of about 30 variations of the D-76 formula.
They found that leaving out the Hydroquinone made almost no
difference in the gamma or density. It appears that
Hydroquinone is almost inactive as a reducing agent at the
low pH of D-76 but does act to regenerate the Metol
resulting in longer developer life.
It appears that in a formula using Sulfite and Borax the
amount of Metol should be around 5 grams but it will develop
well at 2 grams if relatively low capacity is acceptable. Of
course, without the Hydroquinone the slow rise in pH does
not occur and the buffer system is not necessary.
Because Metol will develop even in weakly acid
conditions a Sulfite solution is sufficient to ionize it and
make it active. The early investigators missed this or they
would have developed D-23 about fifteen years earlier than
they did.
Also note that about 80 grams per liter of Sulfite is
optimum as pointed out by Ryuji Suzuki. This is the amount
used by Agfa in their version of D-76.
D-76 was the one of the first developers to be designed
with any understanding of how developers work. It was
originally formulated by John Capstaff, of Kodak, as a fine
grain developer for a new duplicating film for motion
picture negatives but was adopted as the standard negative
developer rather quickly due to its fine grain and
reliability in comparison to the other developers in general
use at the time. Capstaff, BTW, was responsible for
developing home movies, in particular the use of 16mm (and
later 8mm) film and the reversal process. He also did
considerable work on the old lenticular color film sold by
Kodak under the Kodacolor name in the early 1930's but
having no relation to the later film of the same name.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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