Diluted D-76 & Imporved D-76 at dilution

"Keith Tapscott."
wrote in message
...

In the British Photographic Almanac 1957, the D-76d
formula (also known
as Ilford ID-166) was the developer used to compare some
of the then,
new PQ fine-grain developers designed by Kendall and
Axford which led
to the introduction of Ilford Microphen.

The MQ buffered-borax developer lost activity and
effective film speed
quickly when KBr was was raised above 0.25 grams per litre
of
stock-solution. Developers such as Ilford ID-68 and
Microphen had good
stability and working capacity with negligible loss of
film speed
compared to the MQ developer with reuse and with minimal
increase in
graininess compared to D-76d.

Unfortunately, Ilford discontinued Microphen replenisher a
long time
ago. Ilford DD designed for Dip & Dunk processors and it`s
amateur
variant DDX are buffered-borax developers which fully
exploit film
speed. Perhaps in the fullness of time, these developers
will remain
while Microphen might be discontinued.
Xtol is an interesting alternative to D-76 and Microphen.
It would be
nice if Kodak designed a liquid concentrate similar to DDX
based on
their Xtol formula.




--
Keith Tapscott.

I have never heard of this before Kendall and Axford are
well recognized photo scientists. Do you have a citation to
this work? In the old D-76 paper it was found that about
0.25 gram of bromide suppressed the slight fog typical of
_fresh_ D-76 resulting in a slight increase in film speed.
As far as reliability and activity is concerned remember
that buffered D-76 used with replenishment was a standard
developer for motion picture negative development for many
years. It would not have been if not reliable.
Adding bromide does lose film speed but does not affect
devloper activity, they are different functions.
Microphen is essentially buffered D-76 with Phenidone
substituted for metol and adjustments made for the required
pH. It requires some bromide due to the propensity of
Phenidone to produce fog. However, benzotriazole is more
effective because the anti-fog property of bromide is not
very effective with Phenidone. Microphen is not quite the
same as the published formula, for one thing it has a
different pH.
D-23 will mostly duplicate the results of D-76 as far as
film speed and grain but is not as long lived and can not be
replenished as long as D-76. The mutually regenerative
effects of metol and hyroquinone in D-76 extend its useful
life considerably.
I don't understand why you found development times with
buffered D-76 so long. It has the same activity and pH as
fresh standard D-76. The comparisons were done long ago by
Crabreee, et.al. in their 1929 paper.


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