Quote:
Originally Posted by Richard Knoppow
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.
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Richard Knoppow
Los Angeles, CA, USA
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(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.