Dk-76.

I saw a formula for a developer called DK-76 which is the basic D-76/ID-11 formula, except that the Borax is replaced with an equal weight of Sodium Metaborate. Is this an official `Kodak` formula?

http://www.digitaltruth.com/techdata/dk76.php

Keith Tapscott. wrote:
I saw a formula for a developer called DK-76 which is the basic
D-76/ID-11 formula, except that the Borax is replaced with an equal
weight of Sodium Metaborate. Is this an official `Kodak` formula?

http://www.digitaltruth.com/techdata/dk76.php

Yes. At one time it was believed to give better shadow detail. I do not know
if that was true or not.

D-76d is yet another similar formula, but its buffering is better. Its main
advantage is that it does not gain strength with exposure to air (as in a
partly filled bottle). It is the same as D-76, but instead of 2 gm/l of
borax, it uses 8 gm/l of borax and 8 gm/l of boric acid. Many believe that
is what you get if you buy commercial D-76.

--
.~. Jean-David Beyer Registered Linux User 85642.
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"Keith Tapscott."
wrote in message
...

I saw a formula for a developer called DK-76 which is the
basic
D-76/ID-11 formula, except that the Borax is replaced with
an equal
weight of Sodium Metaborate. Is this an official `Kodak`
formula?

http://www.digitaltruth.com/techdata/dk76.php




--
Keith Tapscott.

It is although it was first published as Kodalk D-76
without the DK prefix. At the time it was thought that the
metaboate would be able to buffer the pH of the developer
but it was not effective so the buffered version D-76d,
announced in 1929 remains the preferred version. DK-76 was
formulated at the time Kodalk was made available by Kodak
who published several developer and fixer formulas using it
at the time. Kodak did not invent metaborate but did patent
an economical method of producing it.
The buffering is made necessary by a slow increase in pH
in the original D-76 which affects its activity enough to
cause problems in predicting results. This effect is caused
by a slow reaction between the hydroquinone and the sodium
sulfite which results in a small amount of sodium hydroxide.
This effect was discovered shortly after the D-76 formula
was first published (1927) and a research project at Kodak
Labs resulted in the buffered version D-76. The researchers
did not discover the cause of the pH increase, only that it
did increase. The discovery of the hydroquinone/sulfite
reaction was not made until the 1950s. For reference here
are the two formulas:

D-76 (original)
Water (at 125F) 750.0 ml
Metol 2.0 grams
Sodium sulfite, desiccated 100.0 grams
Hydroquinone 5.0 grams
Borax, granulated 2.0 grams
Water to make 1.0 liter

The buffered version is:
D76d
Water (at 125F) 750.0 ml
Metol 2.0 grams
Sodium sulfite, desiccated 100.0 grams
Hydroquinone 5.0 grams
Borax, granulated 8.0 grams
Boric acid, crystaline 8.0 grams
Water to make 1.0 liter

The above has the same activity as the original formula when
its freshly mixed and retains that activity in storage. The
activity can be varied over a wide range by changing the
ratio of borax to boric acid.

The Kodalk version is the same as the original version but
uses 2.0 grams of Kodalk (sodium metaborate, octahydrate) in
place of the borax.

Current packaged D-76 is the buffered version.

Virtually every film maker has published some version of
D-76, they are all pretty similar in practical results.
Kodak seems to have been the only one to recognize the
necessity for buffering.


--
---
Richard Knoppow
Los Angeles, CA, USA

Thanks Jean-David and Richard for replying. I had not seen the DK-76 formula in any of my own Kodak publications and wasn`t sure if it was a genuine Kodak formula, thanks for clarifying.
I suspect that both Ilford as well as Kodak may well have made some subtle modifications to the basic formula over the years, I also suspect that the current Ilford ID-11R replenisher is close to the "modified" replenisher on page 17 of Kodak publication `03`. I have seen some excellent prints from a former commercial photographer who uses replenished ID-11 for processing B&W sheet-films. See page 7 of the ID-11 technical information "Replenishment"..
http://www.ilfordphoto.com/Webfiles/...1159472874.pdf

Originally Posted by Richard Knoppow

It is although it was first published as Kodalk D-76
without the DK prefix. At the time it was thought that the
metaborate would be able to buffer the pH of the developer
but it was not effective so the buffered version D-76d,
announced in 1929 remains the preferred version. DK-76 was
formulated at the time Kodalk was made available by Kodak
who published several developer and fixer formulas using it
at the time. Kodak did not invent metaborate but did patent
an economical method of producing it.

Virtually every film maker has published some version of
D-76, they are all pretty similar in practical results.
Kodak seems to have been the only one to recognize the
necessity for buffering.


--
---
Richard Knoppow
Los Angeles, CA, USA