Some thoughts on seasoning and steady state

Discussion in 'B&W: Film, Paper, Chemistry' started by Photo Engineer, Aug 16, 2009.

  1. Photo Engineer

    Photo Engineer Subscriber

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    I have been reading several threads lately that discuss replenishment and several older threads stick in my mind that covered steady state seasoning and replenishment.

    It seems that there is a great misunderstanding over the situation with both seasoned developers and with the steady state of seasoned developers.

    First off, let me state that I fully understand that by many definitions, steady state excludes startup and shutdown of a given process. Now, understand this. If, in photography, steady state did not include startup and shutdown, a lot of customer’s films would be ruined every time a photo lab charged their machine(s) with new developers. The startup in a photo process must yield the same results as the seasoned one as closely as is possible.

    In the case of D-76, it is achieved by D-76 as startup and D-76R as replenisher. Each of these have different formulations and used separately would yield different results. Used properly, they will give you a constant result from startup to shutdown thus giving the effect of a steady state condition. The tank developer does not resemble either the fresh developer or the replenisher (see below).

    In other words, fresh D-76 and replenished seasoned D-76 should give close to the same results. I know that there are some differences, but this is due to unavoidable leaching of development byproducts and chemistry into the developer by the wide range of films being put through the process and which cannot be perfectly compensated for due to the variety of films one may use.

    In the final analysis, the steady state may yield the same characteristic curve, sharpness, speed and grain as the fresh developer, but it does it by a slightly different chemical composition. So, for example, the final seasoned D-76 in the tank contains Iodide and Bromide and neither the startup developer nor the replenisher did. But, the seasoned developer also has a different blend of HQ, Metol and alkali. This balance is changed to reflect not a steady state in chemical analysis necessarily, but rather, as closely as possible, it represents a steady state in the film’s characteristics when processed in the ever changing developer. In other words, the film’s steady state remains constant from startup through equilibrium and no customer film is lost even though the chemistry in the tank is undergoing a change from startup to steady state or equilibrium.

    Even some excellent engineers and chemists seem to miss this point. Since it is not a generally published topic, nor is the condition easy to analyze for, it is often misinterpreted or overlooked. I thought I might shed some light on it.

    So, steady state can refer to the condition of the developer solution composition, or to the state of the results obtained from the process, or both. In photography it mainly refers to the results obtained. And, in so doing, it must encompass the startup and continuous running or we would be ruining a lot of customer film in photo labs. I think that you can see that what I have described above is obvious.

    A photofinisher cannot run blank film through his process to season a fresh tank of developer. It is not cost effective. The developer must be right at startup. The same goes for us when we mix up new developer. We must not be required to season that developer. It must be at a steady state at startup to yield the proper results.

    I hope I have clarified things for some people.

    PE
     
  2. Ian Grant

    Ian Grant Subscriber

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    But seasoned/used D76 doesn't ever give quite the same results as fresh D76, nor do other developers used in a similar way.

    We aren't disagreeing because the in fact the seasoned/replenished D76 has some characteristics of D76 used fresh FS and others more akin to diluted 1+1/1+3 which are actually beneficial to sharpness, tonality , and finer grain.

    Variations to replenishment have been made for similar commercial developers depending on whether the replenishment is on a bleed system or topping up. (Axford & Kendall's Ilford Commercial PQ variant of D76).

    Ian
     
  3. Photo Engineer

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    Ian;

    I did say it was not exact, but the alternative is a very large difference between fresh and seasoned. There is no huge difference. The actual differences are very tiny or customers would reject their film as being misprocessed. I think you can agree to that.

    PE
     
  4. Ian Grant

    Ian Grant Subscriber

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    I did qualify my comments in paragraph two :D by saying that the differences are actually beneficial, there are improvements in quality.

    That's why I'm a strong advocate for using replenished developers where possible. Over the years (since 1969) I've used Microphen (ID-68), ID-11/D76, Adox borax MQ as well as Xtol replenished, either in deep tanks or 2.5 litre containers. All those developers are superb replenished and negative qualities improve compare to using fresh developer at Full Strength.

    Ian
     
  5. Photo Engineer

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    I think you will find that the average user can usually not spot the difference. Or, that the difference is not important enough to comment on, and that is my point. The developer varies quite a bit as it seasons and is replenished, but the final result varies hardly at all. And, the variation is not important to the average user.

    PE
     
  6. Ian Grant

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    In a commercial situation where 3 photographers were using a 5 litre deep tank system we all found quite a significant increase in negative quality once a fresh batch of developer was seasoned & ripened properly.

    The ID-11 (D76) was worked hard with probably an average of at least 5 or 6 rolls of 120 & a dozen 5x4's being processed every day, no-one particularly liked being the first to use the freshly mixed & seasoned developer, even worse was when a batch was contaminated and we had to use completely fresh developer.

    There's definitely a noticeable difference in using well replenished D76 compared to fresh D76, in terms of negative quality which shows in the final prints.

    But as you say not everyone might spot the differences.

    Ian
     
  7. BetterSense

    BetterSense Member

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    I use replenished D23. I mix up a new batch when I have added 1/2 the original volume of replenisher.

    I think I understand what you are saying here. In other words, developing films changes the chemical composition of the developer, and the replenisher is designed to do whatever it needs to do to compensate for these changes--not necessarily to remove them--so that the final result is (approximately) constant throughout the use.

    What are your thoughts on "seasoning" a new batch of developer with a bit of the old heavily-replenished developer? A help for consistency or just an unnecessary contamination of the fresh batch?

    Perhaps I am an average user, and I can back you up on that. People have told me that there are differences, and that I should use one-shot chemicals for consistency, but I've never noticed any differences between fresh developer and well-replenished developer. I don't see how you could detect small differences anyway if you are shooting roll film.
     
  8. Photo Engineer

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    Well, you can use any method you want, the basic system is designed to work with batch replenishment or by using flow meters. As for the variations between fresh and seasoned, it is there, but in terms of quality, it is minor. After all, fresh and seasoned color processes work just fine except for a tiny shift in color balance in some cases. I think that even this has been worked out in recent years.

    At Cape Canaveral we ran thousands of feet of MP film a month and did not have to "run in" fresh developer before quality was up to release standards. In the lab I worked in in college, we did not run in. And, at Kodak we worked with fresh developer and measured release standards, while the release technicians worked with seasoned developers. Our data were comparable in terms of all release characteristics within tolerances.

    PE
     
  9. fotch

    fotch Member

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    Don't take this the wrong way but if you can see it and others do not, maybe this is like the placebo effect. Because you believe in this replenishment effect, you see what you want to see and others don't?

    Just a thought.
     
  10. Ian Grant

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    It's well known that the quality improves, and has been observed by plenty of other photographers and been well written about. But replenishment is rarely used outside commercial darkrooms, and even less so by amateurs.

    Ian
     
  11. Photo Engineer

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    If there was a significant difference, I think that the manufacurers would be moved by the commercial and professional photographers to publish this fact and the data. As is, they support one "aim" from each developer and do not mention the seasoned state for the most part.

    I think that Fotch has a point that cannot be dismissed. Many of the "well known" sources are years old and many had single tests, that they said were lower in quality. They did no have side-by-side adjusted comparisons.

    PE
     
  12. sanking

    sanking Member

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    I am just curious about this. How many laboratories in the world are still processing B&W film in systems that require replenishment. My assumption was that service was already history virtually everywhere. It certainly does not exist in my home town.

    Sandy King
     
  13. BetterSense

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    Next time I mix up a fresh batch of d23, I should shoot two identical negatives of a contrast ramp (which I don't have, but I could use a 'real' scene or something else) and develop one of them for X minutes at Y temperature in the old, replenished developer. Then after my fresh batch is done, I should develop the other negative in the fresh batch using the same time/temp, and make a straight print using the same time on the enlarger. Anyone want to make any bets as to what differences I observe?
     
  14. MartinP

    MartinP Member

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    Well, the replenished tanks last for ages with floating lids, and the cost is minimal if any volume at all of black-and-white film comes in to be processed. The last lab I worked in used then, and still uses, replenished D76 controlled with test-strips to control the amount of replenisher.

    The rolls and sheets went up to 10"x8" and got dunked using stainless-steel frames and cages. All very standard stuff for decades.
     
  15. Photo Engineer

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    Sandy;

    There is a fairly big operation in NYC that does a lot of custom B&W. It is called SixtyeightDegrees. Another is an APUG sponsor doing custom B&W work. So, this is by no means a vanished type of process.

    PE
     
  16. nworth

    nworth Subscriber

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  17. BetterSense

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    Replenishment is eminently practical even for the hobbyist, because it's cheap, and convenient. 1 liter of d23 can develop 25 rolls of film, and costs only about $2 making for a very cheap per-roll cost of like 5 cents. D76 used one-shot was costing me 25-60 cents per roll, and I had to mix up the powders and so on.

    If you think there is some disadvantage in quality, I can see how you would come to that conclusion. But since I feel there is NO quality penalty to do this it seems rather practical to me even though I only shoot a couple rolls a week. Next on my list to try is replenished Xtol; I hear it works out pretty well too.
     
  18. Photo Engineer

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    This is a very important statement. My reply is rather easy though.

    1. D-76 is old, but in spite of that replenishsment with it still works by giving the same (or virtually the same, depending on POV) observed results with modern films and with old type films in spite of the differences in chemistry. In fact, that caveat in prens above may be due more to the mixes of film in commercial operations than for any other reason. I might add that many other developers do as well or better. XTOL does the job by being its own replenisher, and that is the result of a modern formulations with modern films. So, this addresses one point.

    2. Your comment seems to feel I am suggesting replenishment, but in fact, I was answering some threads and posts here and elsewhere, and also some e-mails and PMs which indicated to me that there were some people who did not understand the way the replenishment process worked. I am not advocating that anyone change. If it works, use it!

    PE