[pure-silver] Re: Buyer found for AGFA Photo
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 27 Nov 2005 19:47:03 -0800
----- Original Message -----
From: "DarkroomMagic" <info@xxxxxxxxxxxxxxxx>
To: "PureSilverNew" <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, November 27, 2005 6:42 PM
Subject: [pure-silver] Re: Buyer found for AGFA Photo
Charlie
If mixing your own chemicals is not your thing, don¹t worry.
Try ID-11 at the same dilution and for the same time as D76.
They are
practically identical. As Richard said D76 is buffered and
ID-11 is not.
Both developers gain strength with age if subjected to air
(oxidize and pH
increase), and the buffer is there to compensate for that.
Nevertheless, I
typically mix ID-11 as a stock solution of 1 or 2.5l, and
then immediately
fill 150ml olive glasses with it all the way to the rim. I
make sure that
there is only a tiny bubble of air and that the cap is
tightly sealed.
Stored that way at room temperature, I have used ID-11 after
6 months
without any ill effect. Once I missed a glass at the back of
the shelve and
found it 18 months later. It also worked just fine.
Sometimes, there is some
brown debris at the bottom of the glass or tiny white
crystals, but after
shaking the glass a bit, they go back into solution quickly.
Good luck.
Regards
Ralph W. Lambrecht
http://www.darkroomagic.com
I am not sure the rise in pH of standard D-76 requires
oxidation. It happens as a slow reaction between the sulfite
and hydroquinone and, if my understanding is right, the
reaction goes on in unused stored developer. The buffering
is able to counteract the pH change. This problem and
solution were described in a 1929 paper by Carlton and
Crabtree of Kodak labs. They also showed the results of
about 30 variations of the D-76 formula. According to Ryuji
Suzuki, the optimum amount of sulfite for developers of this
sort is around 80 grams per liter. I am not sure this makes
a very big difference but it must make some. He reports that
Agfa 17 is closer to optimum than D-76. I think he has a
more optmized formula on his web site.
In their paper Carlton and Crabtree show the results of
development in D-76 of various ages for constant density.
After about 3 months the time needed to reach a the density
is nearly halved.
ID-11 may attack this problem in another way, I don't
know. In any case, the buffered version is easy to make up
and even the standard version will not cause problems if its
used within a reasonably short time of mixing.
There is a great deal in the literature on D-76 type
developers because they became the standard for the motion
picture industry rather quickly and remained so until color
displaced B&W for most movies. Even the current Kodak
developer for machine processing of motion picture film,
D-97, is a variation of D-76. Next year will mark the 80th
anniversary of this developer.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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