Film developer replenishment

I've been using replenished D23 for 15 years in the normal fashion of 22ml of D23R per role of 36. Recently I came into a nice laboratory grade pH meter and started tracking developer pH over time and replenishment. I noticed that D23 pH increased at a rate closely matching the volume of D23R used eventually reaching a similar pH as the D23R. The effect on development is consistent with increasing pH and I learned along time ago to shave development time about 1 minute/500ml of D23R based on film tests. I'm wondering now if pH can be used to vary the volume of D23R per roll in order to maintain consistent D23 pH or is the increasing pH actually necessary (and as designed) to keep the other ingredients active?

It would help to know the formula of your D-23R, since I can't seem to find the formula.

I've heard people are using DK-25 R as replenisher using this formula:

DK-25 R :
Water 750 ml
Metol 10 grams
Sulfite 100 grams
Sodium metaborate 20 grams
water to make 1 liter

as the base D-23 is not buffered, I'd expect any replenisher formula with an alkali will raise the pH, up to the point that it matches the replenishing formula.

I rarely ever used D-23 and never replenished, but it would seem reasonable to me that if you'd want to replenish it, you'd have to add some kind of alkali to counter the bromide build-up.

It's been a while, like 30 years, since I ran a replenished sink line. But back then, Kodak's recommendations were to replace the developer who you'd added enough replenisher to equal the original amount of developer. That was true for both D-76 and HC-110B, and it seems a reasonable rule of thumb. I'm not sure how this directly affects you, but it may aid in your thinking.

Kodak says to use D-25R to replenish D23. D25 is:


Here is a list of film developer formulas:

Saganich said:

I'm wondering now if pH can be used to vary the volume of D23R per roll in order to maintain consistent D23 pH or is the increasing pH actually necessary (and as designed) to keep the other ingredients active?

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To an extent. The effects of the use and keeping around of developer are multiple:
* pH shift due to interaction of the developer with the film itself
* oxidization of the developing agents by exposure to aerial oxygen and through the development action itself
* leaching of halides from the developed film into the developer through the development action

If you start with bare D23 and then proceed towards some kind of replenishment system, it's evident that you can only compensate in part for these factors. After all, halides will build up to a certain level, which supposedly should stabilize with an appropriate rate of replenishment. I don't know what the makeup of the D23R replenisher is; apparently it's a higher pH than D23, which I guess should compensate for the halide buildup: the halides act as a restrainer, while the higher pH will increase activity, so to an extent, these effects could balance out.

I say 'could balance out', because getting this exactly right seems virtually impossible to me. I can see how you might achieve a sort of stable process over time, but I don't think it'll ever be as stable as just using the developer one shot. Given the modest cost of formulas like D23, I always considered that to be their main appeal. If there's some image-wise benefit to replenishment, I'd be inclined to just mix a different developer that employs some restrainer and uses a higher pH right from the get-go, and use that one shot. You'll quickly find yourself re-inventing the wheel, of course.

Here's a hint that your replenishment process might be doing what you think it does:

Saganich said:

I noticed that D23 pH increased at a rate closely matching the volume of D23R used eventually reaching a similar pH as the D23R. The effect on development is consistent with increasing pH and I learned along time ago to shave development time about 1 minute/500ml of D23R based on film tests.

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This suggests that your final developer is something in-between D23 and D23R, but closer to the latter. Maybe that's intentional, but I've never quite understood what the appeal is in working with developer that provides inconsistent result for a significant number of rolls, only to (hopefully) somehow balance out at the end. YMMV.

As to trying to track pH to determine appropriate replenishment rates: by measuring pH, you're only assessing one side of the balance. You'd ideally have to determine the halide/restrainer content as well. I don't know of any feasible way to do this in a home darkroom environment.

PS: pH meters tend to be iffy when used at relatively high pH's. Make sure to take proper care for yours; store the probe in the appropriate solution and regularly calibrate your meter if only to verify that you're still getting consistent readings. A drift of 0.2pH seems minor and can easily occur, but is big enough to make the reading entirely useless (or worse - it'll lead you out into the woods).

Thanks Koraks, you explained the situation well and I feel less naïve regarding the chemistry. The only benefit for replenishment is it saves me time and I can keep up with processing due to limited time and constraints on space. I used to use Hc110, Rodinal, and various other concentrated formulas for efficiency, but came back to D23. Naturally I like to test the limits so between July 2023 and June 2024 I ran 40 roles through 1 liter of D23, which was about 1 liter of D23R. At some point, about 700ml through the D23R midtones started disappearing. Tracking the pH I can see that the rate of increase accelerated after 500ml of D23R, 7.9 to 8.2 for first 500ml, then 8.2 to 9.2 for next 500ml. Anyway, it seems I can't get away with using a full liter of D23R, which was what I was curious about.

See here:


and here:

Saganich said:

The only benefit for replenishment is it saves me time and I can keep up with processing due to limited time and constraints on space.

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Ah, OK, I see; yes, that makes sense. I think in your place, I'd be tempted to revisit the highly concentrated developers again, seeing if there's something in there that might do what you like about D23, but with the added benefits of consistency as well as space savings. Have you tried pyrocat?

I have a litre of D76 that I replenish as I use. I mix up 500ml of D76R and, when that's used, I use the remaining replenished D76 1:1. The current bottle of D76 has been in use for around 6 months - the replenisher is almost gone.

D23 is a different thing to begin with, though. Being only metol and sulphite, it dies very rapidly with use and so the replenisher requires a source of alkalinity to bring it back to life. So, is it even the same developer once replenished? Sort of?

A great advantage of replenished developer is that the bottle is always full. But the replenisher bottle is not. Once 400 of the 500ml in my replenisher bottle is gone, I start to get suspicious about the remaining 100ml.

Don_ih said:

So, is it even the same developer once replenished? Sort of?

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I doubt it. D76 is of course strongly buffered through a borate buffer, contrary to D23.

koraks said:

I doubt it. D76 is of course strongly buffered through a borate buffer, contrary to D23.

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D23R contains sodium metaborate.

Yes, and that underlines the validity of the question you asked and that I quoted. D23 is an unbuffered developer, replenished D23 is a different developer as it's buffered, although it may or may not act sort of similarly to D23, depending (see my earlier post), D76 is a buffered developer to begin with, but it will also likely go through at least subtle changes as it's taken from an initial mix to a replenished state.

In its literature Kodak seemed to treat replenishment of D-23 and D-25 (both using the the D-25 replenisher formula) as more of a compromise than usual, with good reason. In the case of D-23 the instruction was to discard the replenished developer after approximately the equivalent of 26 rolls per litre by which time 600ml of replenisher solution would have been added.

Don_ih said:

I have a litre of D76 that I replenish as I use. I mix up 500ml of D76R and, when that's used, I use the remaining replenished D76 1:1. The current bottle of D76 has been in use for around 6 months - the replenisher is almost gone.

D23 is a different thing to begin with, though. Being only metol and sulphite, it dies very rapidly with use and so the replenisher requires a source of alkalinity to bring it back to life. So, is it even the same developer once replenished? Sort of?

A great advantage of replenished developer is that the bottle is always full. But the replenisher bottle is not. Once 400 of the 500ml in my replenisher bottle is gone, I start to get suspicious about the remaining 100ml.

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Out of curiosity, is your starting 1L solution "official" Kodak D76 or is it made using one of the readily available formulaes?

I have been looking into starting to use D76 replenished(partially because my 70mm tank needs 1.75L of working solution, which even diluted 1:3 is a LOT of developer). I have read-and I don't know how true this is-that the current commercial D76 is not quite the same as the familiar published formula, and in fact I've seen it stated that it may be using a metol variant/derivative and not metol as we would typically use to blend it.

Since Kodak no longer makes D76R, I'm leary of attempting replenishment with commercial D76 and a home-made replenisher. That, along with a gallon bag now being ~$16, means that the bottle of packaged Kodak I have mixed now may be my last Kodak-branded D76...

Ben Hutcherson said:

Out of curiosity, is your starting 1L solution "official" Kodak D76 or is it made using one of the readily available formulaes?

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It's the formula for D76 that's been used by people who mix from scratch for about 90 years. If I was to use an envelope of Kodak or whoever's D76, I would probably just use it one-shot (at 1:1). If I have the stuff to mix up replenisher, I have the stuff to mix up D76 - because it's the same stuff.

koraks said:

replenished D23 is a different developer as it's buffered, although it may or may not act sort of similarly to D23

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I've never replenished D23. A character of D23 unreplenished is that it loses power quickly, which can have an impact on how a sheet of film develops, depending on agitation. Any amount of an alkaline would change that way that works - it wouldn't get spent as quickly in a low-agitation situation. I've read some people carry over old replenished stock into their fresh D23 to "ripen" their new stock so it behaves properly, when they routinely use it replenished. So, it's like two different developers. There's the "raw" D23 people will mix up, use, then discard and the replenished D23 that probably behaves a bit more like a less-aggresive D76.

koraks said:

Ah, OK, I see; yes, that makes sense. I think in your place, I'd be tempted to revisit the highly concentrated developers again, seeing if there's something in there that might do what you like about D23, but with the added benefits of consistency as well as space savings. Have you tried pyrocat?

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Yea, I went down the concentrated developer path awhile back. I hit the HC110 and Rodinal bottles, then started mixing Beutler variants before settling on just D23. Then I got acquainted with the FX school, FX2 being quite nice but a PITA to manage consistency. Next came DiXactol, FA1027, before having a good year with Pyrocat and an Aristo VC head, all of which were fine. Then went back with concocting variations on D23 using small amounts of borax and other 2nd bath components for contrast control. This also included some D76 variants and D96 replenished when I abandoned TriX for Double-X last year. This doesn't include the paper developers. I suppose I have chemistry to make anything in the solvent developer menu and prefer that to purchasing products, a bit of a contradiction I know. Looking back right now I'm curious about Pyrocat and XX, since that's what I'm shooting and I need the full 200 ASA on XX so Pyrocat might be fine but I've been shy about it for two reasons, working with pyrocatechin and originally I had it fail me out of the blue (same happened with D76) my fault because I wasn't paying attention to shelf life, but emotionally it sent me back to D23.

Anyway, this was a nice stroll down memory lane, lol, I mixed up another liter of D23 and a liter of D23R. Just for fun I ran 4 rolls through the completely replenished old D23 and 3 rolls in the fresh D23. When I scanned all the film I didn't track which rolls went into the old or new D23, and any difference attributable to the developer, or in other words any effect of old developer didn't seem to rise above the noise of all the other variables across the frames. But my experience is that the old developer starts to feel like the midtones are being compressed. Yea, the replenished D23 has a sweet spot for sure. I ripen the the fresh mix a bit by topping off the bottle with about 100ml of old developer, which also eliminated the air space in the bottle. Also I won't start replenishing until the 4th roll.

Don_ih said:

. A character of D23 unreplenished is that it loses power quickly, which can have an impact on how a sheet of film develops, depending on agitation.

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Does the above statement indicate that unreplenished stock solution loses its power quickly when left in its container or is this unreplenished stock that has been used, say once, either at 1+1 or 1+3, and then an attempt is made to use the same stock or dilution again at some point thereafter.. If it's the latter then how quickly do you have to use it again to develop a second film?

I had always thought that once used either as stock or in diluted form it had to be discarded anyway but that unused stock solution kept for at least 6 months

Thanks

pentaxuser

Milpool said:

In its literature Kodak seemed to treat replenishment of D-23 and D-25 (both using the the D-25 replenisher formula) as more of a compromise than usual, with good reason. In the case of D-23 the instruction was to discard the replenished developer after approximately the equivalent of 26 rolls per litre by which time 600ml of replenisher solution would have been added.

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I haven't read that but it tracks with my experience, after 600-700 ml something not good starts to happen. I thought maybe it had something to do with pH rate of change increasing at about that point, the hypotheses of too much replenishment. If I had a guide (like pH) to use to tweak volume of replenishment then I could go a full 1000ml replenishment or more, but it's fine mixing new at 500ml.

pentaxuser said:

Does the above statement indicate that unreplenished stock solution loses its power quickly when left in its container or is this unreplenished stock that has been used, say once, either at 1+1 or 1+3, and then an attempt is made to use the same stock or dilution again at some point thereafter.. If it's the latter then how quickly do you have to use it again to develop a second film?

I had always thought that once used either as stock or in diluted form it had to be discarded anyway but that unused stock solution kept for at least 6 months

Thanks

pentaxuser

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Unreplenished D23 can be used for many roles of film with adjustment to developer time, like +10% per roll. For example at 9 minutes I'm good with raw D23 but after 150-200 ml of replenisher that 9 minutes is now a +1. Between 100ml and 500ml replenishment I find it to be very consistent time wise. You can see where roughly the 100ml and 600ml points are in the first graph but the second graph the pH rise was more rapid maybe because I developed much more film in that time. The pH may not be an important measure other than an indicator when you should mix up more.

pentaxuser said:

Does the above statement indicate that unreplenished stock solution loses its power quickly when left in its container or is this unreplenished stock that has been used, say once, either at 1+1 or 1+3, and then an attempt is made to use the same stock or dilution again at some point thereafter.. If it's the latter then how quickly do you have to use it again to develop a second film?

I had always thought that once used either as stock or in diluted form it had to be discarded anyway but that unused stock solution kept for at least 6 months

Thanks

pentaxuser

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According to Kodak, D-23 stock solutions have the same keeping properties as D-76.

Incidentally there's good information on this (including keeping properties) in publication J-1. Regarding replenishment more generally, O-3 is another good reference.

Over Christmas I had been reading about D23 replenished with DK25R.
A nice coincidence that this thread should appear now.

The information I have read said to make 1 litre then after initially developing 3-4 films in the same litre, start replenishing with 22ml of DK25r per roll of film used.

The tank I will be using takes over 1 litre. Pretend it is 1.5 litres. It keeps the sums simple.
I am actually going to be developing sheets of 4x5 but using roll film for the example makes it easier to understand.

If I develop one film in 1.5 litres, is it still just 22 ml of replenisher, or 22 +11 ml of replenisher ? The extra 11 ml for the extra 0.5 litres of used developer.

Just thinking outloud a bit, aside from economy, I was under the impression that one of the benefits, so to speak, of using a replenished system was that after it was appropriately "seasoned" by developing a few rolls of film, that the replenisher would more or less keep the system operating the same at least until complete EOL of the developer. I know some replenishment schemes(XTOL comes to mind) call for replenishing by adding stock solution. Others, like D76 or D23, with a dedicated replinisher, omit some of the ingredients of the stock solution while the amounts and ratios of other components(developing agents, borax, sulfite, etc) is different from stock.

Since D23 is about the cheapest and simplest developer I know of to DIY mix, and if replenishment causes constantly drifting properties, it would be hard for me to make an argument for running it replenished...

Saganich said:

Pyrocat might be fine but I've been shy about it for two reasons, working with pyrocatechin and originally I had it fail me out of the blue (same happened with D76)

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Neither should be much of a problem; it's easy to work safely with pyrocatechol as it doesn't tend to kick up a lot of dust anyways, and if it concerns you, just wear a face mask. For longevity mix the pyrocat in glycol and only mix small batches at a time; that way it virtually cannot die before you use it up.

Ben Hutcherson said:

Just thinking outloud a bit, aside from economy, I was under the impression that one of the benefits, so to speak, of using a replenished system was that after it was appropriately "seasoned" by developing a few rolls of film, that the replenisher would more or less keep the system operating the same at least until complete EOL of the developer. I know some replenishment schemes(XTOL comes to mind) call for replenishing by adding stock solution. Others, like D76 or D23, with a dedicated replinisher, omit some of the ingredients of the stock solution while the amounts and ratios of other components(developing agents, borax, sulfite, etc) is different from stock.

Since D23 is about the cheapest and simplest developer I know of to DIY mix, and if replenishment causes constantly drifting properties, it would be hard for me to make an argument for running it replenished...

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It is nice and consistent over long periods of time with replenishment. It isn't about the cost but the convenience of having it ready to use with confidence even when you don't use it for a few months, or just run 2 rolls per month. I can run 30 rolls through 1 liter of stock over 12 months with no worries. I can let it sit for 6 months and it's fine. What other developer can you say that about except for commercial concentrates like Rodinal or HC110 (I'm sure there are other examples). In other words, the time to mix new D23 is determined not by how old it is, or nasty looking, but by how much replenishment you used.

Replenished developer can easily be used at room temperature, with development time adjusted as needed. I find that really convenient, in my very temperate conditions.