Replenished Xtol getting weak over time

[PFGS]

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).

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.

 

[PFGS]

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).

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.

 

[Maris]

I mixed my Xtol stock in 2007 and have replenished at the rate of 90ml per standard film ever since. For many years my development time for Tmax 400 @68F has been consistent at 11min 15sec. This is definitely weaker than Kodak's recommendation of 7min 15sec but I suspect replenished Xtol activity settles to higher or lower value depending on replenishment rate.

 

[MattKing]

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.

I put together a similar calculation, and ended up with closer numbers. After 28 iterations, 7.23 B/L vs 8.28 B/L.
Let's see if the table is small enough to upload here:
EDIT: ignore attachment - corrected table added later.

 

[PFGS]

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.

 

[Sirius Glass]

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.

 

[PFGS]

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.

Agreed. It was interesting to me because I found the result surprising, didn't really mean to derail the thread. Xtol in general seems to be a "works for most but not for all" kind of developer. I personally have never had a problem with stock, 1:1 or replenished; I'm new to the last of those but have used at least 30L of the stuff over the years, no sudden death or any other issue. Knock on wood I guess.

 

[MattKing]

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.

 

[PFGS]

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.

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.

 

[MattKing]

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.

I have a feeling that Bob Shanebrook could probably add valuable information too.

 

[Raghu Kuvempunagar]

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.

These papers on the math of replenishment might be useful:
https://ieeexplore.ieee.org/document/7250986
https://ieeexplore.ieee.org/document/7254853

Hopefully, somebody in this forum has institutional access to the full text and can help.

 

[Вormental_old]

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.

What is your frequency of development/replenishing and the film volume?

 

[Huub]

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.

I have started in a XTOL-R system more then 2 years ago and haven't run into the weakening issue either. It could have something to do with the amount of film people are putting through it. More film would mean more fresh solution getting added and less chance of the working solution getting weaker by the aging process that affects most developers. I use about 80 films a year, replenishing with 75 ml of stock everytime and I keep the working solution in a 2.7 L bottle.

An other possible cause of the weakening issue could be the quality of the water that is used to dissolve the XTOL. Could it be that small amounts of certain trace elements (iron for instance) in drinking water affect the aging of the working solution? That would also explain the variety of experiences with the keeping properties of the working solution.

 

[koraks]

Could it be that small amounts of certain trace elements (iron for instance) in drinking water affect the aging of the working solution?

Certainly; vitamin C developers are quite sensitive to iron impurities. Good call.

 

[Raghu Kuvempunagar]

For any replenished developer, before one starts using a fresh batch of replenisher, it's a good idea to develop a strip of film in the replenisher (with the same developing time as the stock) and check the results. Typically, a replenisher is designed to be at least as strong as the stock and should give a little more density than the stock. If the test results turn out to be noticeably different then the replenisher is suspect and must be discarded. It's a pity if the well-seasoned stock got spoilt because of an untested replenisher.

 

[Raghu Kuvempunagar]

Could it be that small amounts of certain trace elements (iron for instance) in drinking water affect the aging of the working solution?

This is mostly an unsubstantiated hypothesis as there's no reason to believe that Kodak didn't fix the problem by using an appropriate chelating agent years ago. It should be easy to test the hypothesis yourself by using water that actually contains traces of iron and see what happens.

 

[Sirius Glass]

What is your frequency of development/replenishing and the film volume?

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.

 

[MattKing]

What is your frequency of development/replenishing and the film volume?

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.

 

[Sirius Glass]

I think Bormental was asking about how much film you are developing, and how often.

Since Covid very little. Before 10 to 15 rolls a year.

 

[pentaxuser]

If the replenishment rate is a certain amount per roll then I am unclear why the volume of films will be relevant? What might the link be?

Thanks

pentaxuser

 

[Вormental_old]

@pentaxuser some people reported the need to replenish even if you don't develop, as the developer becomes less active over time. 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.

 

[Donald Qualls]

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.

The theory behind this is that oxidation in storage is a problem. If your storage bottles are good, it's not. Of they're not, replenishing every couple weeks probably won't fix it.

The canonical (i.e. very conservative) shelf life of working solution in a partially full, opened and resealed bottle is two months. Within that length of time, Kodak is confident you'll get the same results you would with fresh developer, and they recommend discarding the solution if you go past that. How replenishing eight times in that period will accomplish anything other than wasting half a liter or so of developer is a mystery. Truly, though, if someone doesn't develop any film at all for two weeks on a regular basis, they probably ought not to try replenishment anyway; instead, take steps to exclude air (to get off the "partially full" time table and onto the "full bottle" time, which is six months with indistinguishable results), one-shot the developer, and don't worry about it.

 

[pentaxuser]

Thanks Bormental for the reason between volume and time and thanks Donald for covering when volume if very low might account for deterioration in what then can become over time a non replenishment situation but in the latter case your post would seem to cover that as well. If all containers including the stock used for replenishment are kept topped up then a long time would seem to need to elapse before any likelihood of deterioration.

pentaxuser

 

[Donald Qualls]

Just to clarify one thing -- I should have typed "stock solution" instead of "working solution" above. For replenishment systems, replenisher is effectively stock solution in terms of storage life, and the replenished stock solution ought to keep fresh indefinitely, but working solution can also refer to diluted stock for one-shot use. Diluted working solution, per Kodak, should not be stored nor replenished -- it should be used shortly after dilution and discarded after use.

I'd propose as a rule of thumb, that if you won't replace the volume of your working solution with replenishment within the two-month time frame, you may not be processing enough for replenishment to be reliable -- so at 70 ml per film, and 1L working solution, that would be about 16 rolls in two months, or on average a couple rolls a week. This might well be conservative -- @PFGS calculated above that a low volume user (like myself) might not even see full seasoning (to steady state condition of the working solution) within a year -- but also note that Kodak's time tables are generally conservative anyway. We have many reports of developers lasting much longer than recommended storage periods.

 

[Вormental_old]

Donald, I agree with your reasoning. However, everything you said is based on one (big) assumption that developer properties do not change over time in the absence of oxygen. I doubt it as there must be solid reasons behind Kodak's stated lifespan of full-strength Xtol as "six months in full, tightly capped bottles". And that's for fresh/clean solution. Development byproducts only complicate the picture.