I agree it would be tough to measure, either objectively or subjectively. So far both my usage of and experience with Xtol-R are closer to yours than his.
What I'd consider "the next question" then is how much B does it take to make a visible (not measurable, since some people can -- or claim they can -- measure a gnat's whisker at a hundred paces) difference in the negatives? The B factor reasonably includes some level of exhaustion, oxidized developer products, dyes from films (for those who don't pre-soak), bromide, and various other things -- but at some point, as noted, it stabilizes; the lower your replenishment level, the higher the stable B value. If you process a mix of 35mm and 120, or (as I do) double load your 120 so a liter of developer gets four rolls, it'll stabilize at some value between the all-35mm, stainless tank value, and the all-120, Paterson tank, one roll per reel value -- even mine, since I don't always have an even number of 120 rolls that need the same time, so I wind up with one, or three, thus less film per liter.
BUT! If that end result, some level of B that we might reasonably expect to run (at 70ml/roll recommended replenishment) somewhere between 13 and 17 B/L, produces consistent negatives, who cares? Aside from the fact your developer might not be fully seasoned until sometime after you mix your second 5L of replenisher...
@Bormental and I have gone back and forth about the difference between him having to add a bunch of time on a specific film and still losing speed -- and me not having to do so and getting good shadows at box speed. It might well be partly due to his much higher processing volume; my developer (with only a bit over a liter of replenisher consumed) likely isn't even really seasoned yet (since I have 2L of working solution, and started replenishing from roll 1, expecting to adjust development when and as needed -- and it hasn't been needed yet), and his, on the third bag of mix, is (was, before the filter incident).
Subsequent iterations are done much like your post where you handled my scenarios sequentially - same calculation but from the new R/L staring point and using a basic formula for mixing different concentrations.We cross posted - I corrected two numbers before you posted.
But generally speaking, in order to analyze your model, can you indicate how you dealt with the next step in each of the two parallel models - which I did initially misunderstand to be sequential).
I put together a similar calculation, and ended up with closer numbers. After 28 iterations, 7.23 B/L vs 8.28 B/L.Subsequent iterations are done much like your post where you handled my scenarios sequentially - same calculation but from the new R/L staring point and using a basic formula for mixing different concentrations.
Modelling the chemical behavior is interesting but it does nothing to find out why a minority of people have the weakening problem. I have used replenished XTOL following the instructions exactly for over a decade and like the vast majority I have not had a problem.
Thanks for catching that, I've fixed that in both tables, and the difference is greater as a result. The corrected tables are added here.Matt, looking only at your second table, the one with VT = 1000:
In the row labeled #4, if "B added to dev tank" is .84, which I believe is correct, then shouldn't "post dev B in dev tank" be 2.84, not 2 as you have it? The .84 from past seasoning + 2 from the new rolls? And all the columns to the right of that subsequently adjusted up, for a B/Liter of that row of 1.6128, not 1.26?
If so, that's in line with my sequence, which reaches 10 B/L after 37 passes but doesn't stabilize at 10.5 until between 300 and 400 passes (by which time some, god know what's really in that jug)
I'll admit that earlier tonight I hit a different sort of jug a little harder than is math-friendly, so let me know if I'm still off.
Thanks for catching that, I've fixed that in both tables, and the difference is greater as a result. The corrected tables are added here.
I don't quite get to 10 B/L after 37 passes (9.78) but the differences are real.
I wonder how the numbers compare for the active components in the developer? There may be enough reserve capacity there that the restraining effects of the development byproducts are more than compensated for by the addition of fresh developer.
I have a feeling that Bob Shanebrook could probably add valuable information too.Given that replenishment is an official and recommended Kodak procedure, I think it must balance out OK? May also be non-linear, like Bormental suggests. Chalk up another reason to miss P.E., he could probably have settled this in very short order.
Given that replenishment is an official and recommended Kodak procedure, I think it must balance out OK? May also be non-linear, like Bormental suggests. Chalk up another reason to miss P.E., he could probably have settled this in very short order.
Modelling the chemical behavior is interesting but it does nothing to find out why a minority of people have the weakening problem. I have used replenished XTOL following the instructions exactly for over a decade and like the vast majority I have not had a problem.
Modelling the chemical behavior is interesting but it does nothing to find out why a minority of people have the weakening problem. I have used replenished XTOL following the instructions exactly for over a decade and like the vast majority I have not had a problem.
Certainly; vitamin C developers are quite sensitive to iron impurities. Good call.Could it be that small amounts of certain trace elements (iron for instance) in drinking water affect the aging of the working solution?
Could it be that small amounts of certain trace elements (iron for instance) in drinking water affect the aging of the working solution?
What is your frequency of development/replenishing and the film volume?
What is your frequency of development/replenishing and the film volume?
I think Bormental was asking about how much film you are developing, and how often.70 ml per roll of 120 film, 135-36, or four 4"x5". If I have not developed film for a while, I do a test strip first.
I think Bormental was asking about how much film you are developing, and how often.
IIRC someone suggesting replenishing 70ml every two weeks even if you don't develop any film. I did not have this issue as my volume is pretty high.
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