From: Richard Knoppow (dickburk@ix.netcom.com)
Date: 07/19/02-12:32:47 AM Z
At 07:45 PM 07/18/2002 -0600, you wrote:
>
>D-19 should still be available. We use it here to process electron
>microscope negatives.
>
>D-76 and D-19 have very similar constituents. D-19 has uses sodium
>Carbonate to raise the pH of the developer. D-76 uses Borax - which has a
>lower pH than Sodium Carbonate. D-19 also has Pottasium Bromide which
>acts as an antifoggant.
>
>If you wanted to experiment you could add some washing soda (washing soda
>is usually made of sodium carbonate) to D-76 - this
>would raise its pH something similar to d-19 - although it will likely
>fog, without any pottasium bromide.
>
>You could get an idea of whether or not D-19 would work in your situation
>
>If the trouble you have with d-76 is a metol skin sensitivity, you might
>want to try Ilford's ID-11. I believe its very similar to d-76 except
>that is uses phenidone instead of metol -people are usually not sensitive
>to phenidone.
>
>Gord
>
>On Thu, 18 Jul 2002, Shannon Stoney wrote:
Gordon, ID-11 is virtually identical to D-76, its also a
Metol-Hydroquinone developer. Ilford Microphen is a Phenidone-Hydroquinone
developer. It has similar characteristics to D-76 but may be tolerable to
those with Metol sensitivity. The best thing is to keep any developer off
your hands.
D-19 has about twice the amount of Hydroquinone as D-76 and a lot of
carbonate to actuate it. The Hyroquinone in D-76, ID-11, and Microphen is
virtually inactive because the pH is too low. Its acts as a preservative
and regenerator for the Metol in the first two and similarly for the
Phenidone in Microphen.
There are other high contrast developers suitable for continuous tone
photography. Dektol 1:1 is an active film developer (or Ilford Bromophen
for a Phenidone equivalent). Its development time is too short for most
modern film, but if grain is not an issue it works fine where somewhat high
contrast negatives are desired.
For reference of those interested in the chemistry of developers here are
the formulas for D-76 and D-19
D-76
Water (at 125F) 750.0 ml
Metol 2.0 grams
Sodium Sulfite, dessicated 100.0 grams
Hydroquinone 5.0 grams
Borax 2.0 grams
Water to make 1.0 liter
The buffered variety has 8.0 grams of Borax and 8.0 grams of Boric Acid
(crystaline).
Up to 20 grams/liter of Borax can be used.
D-19
Water (at 125F) 500.0 ml
Metol 2.2 grams
Sodium sulfite, dessicated 96.0 grams
Hydroquinone 8.8 grams
Sodium Carbonate, monohydrated 56.0 grams
Potassium Bromide 5.0 grams
Water to make 1.0 grams
The high contrast comes from the large amount of Hydroquinone, the large
ratio of Hydroquinone to Metol, and the large amount of carbonate. The
Hydroquinone is quite active in this formula.
The large amount of bromide also contributes the the high contrast
tending to suppress the toe of the image as well as fog.
Compared to D-72/Dektol D-19 has about twice the sulfite and bromide and
about half the carbonate.
For M-H developers the ratio of the two reducing agents is important in
determining the contrast, as well as is the pH. Generally, the more
Hydroquinone predominates the contrastier the developer will be and,
generally, the higher the pH the more contrast there will be until one gets
to very high contrast "process" developers for line work which have
Hydroquinone as the exclusive reducing agent and use Hydroxide as the
alkali (Kodak D-8 for example). Very high contrast developers also usually
employ large amounts of bromide (D-8 has 30 grams/liter) both to suppress
fog and to suppress the development of silver halide particals which have
received low exposure.
---- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com
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