[pure-silver] Re: D-76 and variations
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Mon, 28 Nov 2005 14:41:31 -0800
----- Original Message -----
From: "John Black" <jblack@xxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Monday, November 28, 2005 9:50 AM
Subject: [pure-silver] Re: D-76 and variations
The original D-76 formula and Ilford's published
formula
for ID-11 are:
Water (at 125F or 52C) 750.0 ml
Metol 2.0 grams
Sodium Sulfite, dessicated 100.0 grams
Hydroquinone 5.0 grams
Borax, granulated 2.0 grams
Water to make 1.0 liter
Seems like I remember the OLD original prewar formula for
D76 was
accelerated with Na Carbonate and had a problem with
increasing activity
with aging in solution that was traced to a rise in pH
mediated by the
carbonate. All of which was remedied by switching to
borate
accelerators/buffers. Am I dreaming or was that the case
many years ago?
JB
There was never any version of D-76 with Sodium carbonate
in it. The activity rise, as I mentioned, is evidently the
generation of some sodium hydroxide by a slow reaction
between the sulfite and hydroquinone. At the time the
buffered version was devised (1929) the actual mechanism was
not known but the rise in pH was.
When Kodak began touting Kodalk (sodium metaborate) they
published a D-76 version using it. Its the same as regular
D-76 but has 2 grams per liter of Kodalk in place of the
Borax. This was supposed to be better buffered than the
borax version but was not. AFAIK, it has no virtue over the
standard formula.
Practically every film manufacturer had some variation of
D-76 in its list of formulas. One of the few that seems to
have been the results of some research is Agfa/Ansco 17,
given below. I believe Ryuji Suzuki treats on this on his
silvergrain site.
Agfa 17
Water (125F or 52C) 750.0 ml
Metol 1.5 grams
Sodium sulfite, dessicated 80.0 grams
Hydroquinone 3.0 grams
Borax, granular 3.0 grams
Potassium Bromide 0.5 grams
Water to make 1.0 liter
The amount of sulfite is closer to the optimum for
minimum grain and maximum speed. The small amount of bromide
probably increases effective film speed slightly for unused
developer by suppressing the slight fog characteristic of
D-76 type developers. The same thing was described in the
Carlton and Crabtree paper but they thought the difference
was too small to include the bromide in their formula. When
developer is re-used, replenished or not, there is an
accumulation of bromide in it.
There are a number of old type "fine grain" formulas
containing carbonate. Examples are Agfa 12 and 15
Agfa 12 Fine Grain Tank Developer
Water (at 125F or 52C) 750.0 ml
Metol 8.0 grams
Sodium sulfite, dessicated 125.0 grams
Sodium carbonate, monohydrated 5.75 grams
Potassium bromide 2.5 grams
Water to make 1.0 liter
Agfa 15 is the tray version differing from the above only in
containing
Sodium carbonate, monohydrated 8.0 grams per liter
and
Potassium bromide, 14.0 grams per liter.
I don't think this type of developer has any particular
virtue for modern film. The modern equivalent is Kodak D-23.
There have been two bath developers devised using a
second bath containing carbonate. These really are not
related to D-76 at all. The important property of D-76 is
its use of Borax as the accelerator and the use of
Hydroquinone as a preservative and regenerator of the Metol
rather than as an active developing agent. At the low pH of
D-76 the Hydroquinone, and its reaction products, are
virtually inactive. D-76 will develop fine without the
Hydroquinone but its capacity is more limited.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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