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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 |
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Quote:
(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. Last edited by Keith Tapscott. : December 4th 09 at 03:26 PM. |
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On the subject of buffering with borax or borax+boric acid, this thread may be of interest. There is also a post there by Ian Grant where he provides the formula for the Wellington Borax MQ developer which is actually an older formula than D-76. As Kodalk, wasn`t around back then, think of the formula as being D-50, the forerunner to DK-50.
Ian has worked as a chemical analyst and has an excellent source of photo-formulae.. Borax Project. Last edited by Keith Tapscott. : December 17th 09 at 06:11 PM. |
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Diluted D-76 & Imporved D-76 at dilution
"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. |
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