"Keith Tapscott."
wrote in message
...

Richard Knoppow;848532 Wrote:


I have never heard of this before, Kendall and Axford are
well recognized photo scientists.
(1) DO YOU HAVE A CITATION TO THIS WORK?
*(2) 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.

(3) 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.
*(4) 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.*

(5)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
(1) Yes, I will look for the book
and post the citations here.

(2) I believe that Kodak call D-76d with 0.25 gram of KBr,
SD-21. D-76d
is said to cause higher base-fog than standard D-76/ID-11.

(3) I don`t think the benzotriazole is required in
Microphen types, due
to their low-moderate pH. BZT is often used in PQ
enlarging-paper
developers, along with KBr.

(4) D-23 is a very effective developer, there is a
photographer over on
APUG who uses D-23 replenished and claims to keep it
working over
several months before discarding the old stuff. I have
also seen some
good enlargements made with D-23 processed negatives.

(5) I don`t understand why the times for D-76d are longer
either, but
they are. The film I used was HP5 Plus in D-76d diluted
1+1 and the
negatives were very flat. I gave the time I normally use
with packaged
D-76.

However, the standard formula gave excellent negatives at
the same
dilution. If Kodak are using a different way of buffering
than just
borax or with borax+boric acid, then they must have found
a way to make
the times the same as the standard formula. That is not to
say D-76d is
a bad formula, as long as a suitable time can be found
through
experiment. I think it might be better to use D-76d only
at
full-strength. Even then, I suspect that the times will be
closer to
the basic formula when that is diluted 1+1.

What ever is going on with Kodak`s packaged D-76, then it
is matching
the basic developer for times. D-76d is behaving very
differently from
my own trial with it. Any idea why?

Richard, do you have any raw chemicals of your own to
experiment with?
I ask because it would be interesting to compare your
findings with
mine. The chemicals I have were bought from Rayco in the
UK, although
Silverprint in London are now the main suppliers now that
Rayco has
ceased trading.

Also, is it OK to contact you by PM or the email you have
with your
signature?

Keith.




--
Keith Tapscott.

The answer to the last question is yes, its OK but you
will get a challenge message from the spam blocker at
Earthlink/Netcom. I will unblock you.
I have a few chemicals but my source for many years,
Tri-S Sciences, closed a couple of years ago and I have not
found a replacement although I could get most of the stuff
from Photographer's Formulary. I do have the necessary
equipment to mix stuff, a couple of good scales and the
glassware.
It would be interesting to know the actual pH of mixed
developers. According to Ryuji Suzuki measuring pH of
photographic developers is not trivial partly because the
solutions tend to destroy some types of pH meters.
Packaged D-76 is not the same as the published formula.
For one thing it is modified so that the metol can be
included in the same package as the sulfite. I don't know
how Kodak does this. It also uses boric anhydride which I
believe becomes boric acid in solution.
Original D-76 also causes a slight fog when fresh. When
re-used enough bromide is leached from the film to suppress
this. The 1929 paper shows that a small amount of bromide,
0.5 gram per liter, suppresses this in the fresh developer.
The smaller amount in the Kodak special developer may be
closer to optimum. AGFA also added the bromide to Agfa-17,
their version of D-76 which also has closer to the optimum
amount of sulfite, 85 grams per liter. For reference here is
the formula:
Agfa-17
Water (at about 125F or 52C) 750.0 ml
Metol 1.5 grams
Sodium sulfite, desiccated 80.0 grams
Hydroquinone 3.0 grams
Borax, granular 3.0 grams
Potsasium bromide 0.5 grams
Water to make 1.0 liter

I also found that AGFA had a metaborate version of this
formula. Its identical to the above but has 2.0 grams per
liter of Sodium Metaborate instead of the 3.0 grams of
Borax. Kodak also published a Kodalk version of D-76 called
DK-76, again identical to the original formula but with 2
grams of Kodalk in place of the borax. At the time the
metaborate was supposed to be a better buffer than borax but
evidently it isn't.

I think you are right about the use of bromide rather
than benzotriazole in Microphen. Anti-fog chemicals are most
effective at different pH.