How do you know when to stop reusing a developer?

dcy · May 29, 2025

I am mainly interested in one-shot developers precisely because I want to avoid the complexity of having to figure out when it's OK to reuse a developer, or whether I need to extend the development time or something. Having said that, for my edification, how would one go about deciding when to stop reusing a developer and make a new batch? A couple of concrete examples come to mind:

I plan to use D-76 1+1 one-shot, but I'd love to try D-76 stock to see about that finer grain.
I plan to use D-23 1+1 one-shot, but I'd love to try Barry Thornton's 2-Bath developer just to see what it's like.

I'm wondering if perhaps I can do a "clip test" like the one you use to test the fixer. Like... I could cut a piece of exposed film, put in a beaker, and when it takes longer than X minutes to turn pitch black, it's time to change the developer.

On the topic of Thorton's 2-Bath developer, the published recipe is for making 1L of Part A and 1L of Part B. Would I be right to assume that it's totally fine to make smaller quantities (e.g. 500 mL Part A + 500 mL Part B) as long as I can fully submerge the film?

EDIT: PS --- I know I can't do smaller mixes of D-76 because the powder you get from Kodak is heterogeneous.

Craig · May 29, 2025

For D76, Ilford ID-11 is identical, and the data sheet says 10 rolls per litre, but you must add time compensation per roll.

See the datsheet, pages 7 and 8: https://www.ilfordphoto.com/amfile/file/download/file/1829/product/708/

F4U · May 29, 2025

Your usage rates sound occasional. mix your gallon of D-76 and divide it to 4 bottle, preferably glass bottles filed all the way . The 4th bottle will obviously not be filled totally. Start with that one and use 1:1, one shot.There will be no really big difference in grain or speed that straight for the average photographer. The other 3 bottles may last for years. If you ever smelled D-76 that got so old it turned brown and smells putrid and sickening, you'll know it's bad.

Mr Bill · May 30, 2025

dcy said:
Having said that, for my edification, how would one go about deciding when to stop reusing a developer and make a new batch?

Hi, well, in the amateur world one would generally read the instructions from a reputable manufacturer, then (most likely) do things based on the number of rolls processed. This is not really the ideal way to do things, but in the absence of certain equipment and/or knowledge it mostly suffices. If the manufacturer wants to play it safe (conservative to help protect their customers from failure) they would probably spec a lesser number of rolls per quantity of developer.

The reason "roll count" is not ideal is because developers are actually "exhausted" by the physical quantity of silver developed, not the roll count. But lacking an easy way to check the total amount of silver, assuming an average amount per roll is usually a fairly decent way to go.

In the world of professional processing they use a method somewhat similar to your clip test idea, but more refined. They would periodically process a special test strip known as a "process control strip," then measure the result with an instrument called a densitometer (essentially a light meter for processed film; it reads out the so-called optical density of the film.) Someone would specify acceptable tolerances, then this is used as the guideline for continued use or not. Fwiw this "control strip" usage is generally only used for replenished developer systems where the processing lab would either increase or decrease the replenishment rates in order to keep processing in spec.

If you want to learn more about this sort of thing you could read up on a thing known as the "characteristic curve" of a film. A process control strip would generally use only a couple of exposure points rather than a full curve. These points might be roughly equivalent to photographing both a nominal 18% gray card and a white card. The relative difference between these sorta indicates the "contrast" in the developed film. Stronger development, as a rule, gives higher contrast in this portion of the characteristic curve. And vice versa.

mshchem · May 30, 2025

Buy an old Kodak Darkroom Dataguide. My Dad would mix Microdol-X 1 quart at a time. Store in a 1qt brown glass bottle. He'd affix a gummed paper label to the bottle and make a pencil (#3 hard lead) mark on the label. Time adjustments are given in the dataguide.

Kodak did all the work, you may need to find slightly different times to accommodate new films.

dcy · May 30, 2025

Thanks everyone!

Ok. The clear message is that my best option is to count the number of rolls.

For D-76 / Ilford ID11 @Craig provided a link to an incredibly useful data sheet from Ilford explains exactly what to do.

For Thornton's 2-Bath developer, Pictorial Planet says that 1 L will process 15 rolls, so I'm going to assume that 500 mL will process 7 rolls.

Craig · May 30, 2025

F4U said:
Your usage rates sound occasional. mix your gallon of D-76 and divide it to 4 bottle, preferably glass bottles filed all the way . The 4th bottle will obviously not be filled totally. Start with that one and use 1:1, one shot.There will be no really big difference in grain or speed that straight for the average photographer. The other 3 bottles may last for years.

Wouldn't it be much easier to buy ID-11 in 1 litre packages and mix as needed? Kodak says mixed D76 in full, tightly closed bottles has a life of 6 months, not "years"

Mr Bill · May 30, 2025

dcy said:
I'm wondering if perhaps I can do a "clip test" like the one you use to test the fixer. Like... I could cut a piece of exposed film, put in a beaker, and when it takes longer than X minutes to turn pitch black, it's time to change the developer

For practical use you might be better off to actually shoot off a roll (or just a portion) of a fixed test subject. Same exact scene throughout the roll. Then store the exposed roll somewhere safe. When your developer is fresh clip off an inch or two of this film and develop it. Make sure you cut enough film to have a full negative. Label this developed negative and store it (where you can find it again). Periodically, when you wanna check your developer, clip off another piece of film and develop it. You'll have to visually compare the two on a light table or whatever, and it's strictly on your own judgment.

FWIW if you don't wanna get your processing gear all wet, etc., and you don't mind sitting in the dark for a while, you can hand process just the little strip in a beaker or whatever. Hold it with a film clip, clothespin, disposable forceps, or whatever, and gently swirl it according to your agitation routine.

Takes some time and discipline to do this sort of thing, and probably not worth it to most people. But if you ever get caught in a situation where you seem powerless to figure out what's wrong... well, it might pay off then.

dcy · May 30, 2025

Mr Bill said:
For practical use you might be better off to actually shoot off a roll (or just a portion) of a fixed test subject. Same exact scene throughout the roll. Then store the exposed roll somewhere safe. When your developer is fresh clip off an inch or two of this film and develop it. Make sure you cut enough film to have a full negative. Label this developed negative and store it (where you can find it again). Periodically, when you wanna check your developer, clip off another piece of film and develop it. You'll have to visually compare the two on a light table or whatever, and it's strictly on your own judgment.

FWIW if you don't wanna get your processing gear all wet, etc., and you don't mind sitting in the dark for a while, you can hand process just the little strip in a beaker or whatever. Hold it with a film clip, clothespin, disposable forceps, or whatever, and gently swirl it according to your agitation routine.

Takes some time and discipline to do this sort of thing, and probably not worth it to most people. But if you ever get caught in a situation where you seem powerless to figure out what's wrong... well, it might pay off then.

That's an interesting idea. Thanks.

Mr Bill · May 30, 2025

dcy said:
That's an interesting idea. Thanks.

Sure thing!

One other suggestion... you mentioned using D-76 1:1 and then discard. May I suggest to temporarily pour it into another container after use? Hold on to that used developer until after you have a look at the developed film. If the film looks ok then you can discard the used developer.

Why to do this? Well, every once in a while someone ends up with a completely blank roll of film. And... the used developer is already gone. So no one knows for sure what went wrong. There is always the possibility that you accidentally poured the fixer in first, etc. If you temporarily hold onto the used developer you at least have the option of testing it.

F4U · May 30, 2025

In his book, The Amateur Photographer's Handbook, any edition, Aaron Sussman ,discusses a method of testing developing times based on a clip test and some simple calculation to arrive at a base developing time. I tried it once, years ago. I was surprised it was dead on the money. He also states in another section that if you develop a piece of exposed film that it should never be so opaque as to not be able to see the print on the page of the book if you laid that film on it. The clip test should not be done on a piece of film however that was throroughly exposed in the hot summer sun.. He meant an average zone X exposure of the film. As for putting the stock developer in full glass bottles, kept in a cabinet for years. you'd be surprised.

dcy · May 30, 2025

Mr Bill said:
Sure thing!

One other suggestion... you mentioned using D-76 1:1 and then discard. May I suggest to temporarily pour it into another container after use? Hold on to that used developer until after you have a look at the developed film. If the film looks ok then you can discard the used developer.

Why to do this? Well, every once in a while someone ends up with a completely blank roll of film. And... the used developer is already gone. So no one knows for sure what went wrong. There is always the possibility that you accidentally poured the fixer in first, etc. If you temporarily hold onto the used developer you at least have the option of testing it.

I can do that! Let's hope I never accidentally pour the fixer in first.

Yezishu · May 30, 2025

My method is to use a half-frame camera to shot at different exposure settings (such as 50, 100, 200 ISO). Cut the film into small strips with just 3 to 5 frames. Place the strips into a black film canister, add in 5~10 ml developer in darkness, start agitating. If 5ml sample can effectively develop 3 frames, then I can confidently pour the remaining developer into the developing tank with more frames.

relistan · May 30, 2025

dcy said:
For Thornton's 2-Bath developer, Pictorial Planet says that 1 L will process 15 rolls, so I'm going to assume that 500 mL will process 7 rolls.

Well no, it won’t. The second bath is a pretty good developer after about the third roll, all by itself. That messes with your times and affects the two bath behavior. You will also lose about 20ml of the first bath on each roll you use, for the same reason: carryover. So you should not plan on using the same second bath for all 7 rolls. And by the time you get to 7 in the first bath, be careful that you have enough left to cover your film in your tank.

Raghu Kuvempunagar · May 30, 2025

dcy said:
For Thornton's 2-Bath developer, Pictorial Planet says that 1 L will process 15 rolls, so I'm going to assume that 500 mL will process 7 rolls.

As Karl cautioned, developer carryover can make the second bath in Thornton's a weak developer by itself and complicate things particularly so if the volume is low. If you want to avoid the problem, you can use a one shot second bath based on Ascorbate.

Sirius Glass · May 30, 2025

I always use 35mm test strips before I use a developer. It is a better why to learn that the developer is going or gone than blowing a roll of time to find out.

dcy · May 30, 2025

relistan said:
Well no, it won’t. The second bath is a pretty good developer after about the third roll, all by itself. That messes with your times and affects the two bath behavior. You will also lose about 20ml of the first bath on each roll you use, for the same reason: carryover. So you should not plan on using the same second bath for all 7 rolls. And by the time you get to 7 in the first bath, be careful that you have enough left to cover your film in your tank.

Oh... I'm glad I asked! Thanks.

From what you wrote, here are my options as I see them:

1) 500 mL Parts --- Bad Idea

Theoretically I can make it work. I can make a new Part B every 3 rolls, and I'd have to always develop 1 roll at a time to make sure I cover the film. "Yes", it can work, but it's unnecessary hassle.

2) 1L Parts --- Best Option

Still plan to make a new Part B every 6 rolls, but now there's enough Part A to safely cover 2 rolls of film until the 15th roll. My Patterson tank says that each roll requires 290 mL.

wiltw · May 30, 2025

dcy said:
Thanks everyone!

Ok. The clear message is that my best option is to count the number of rolls.

For D-76 / Ilford ID11 @Craig provided a link to an incredibly useful data sheet from Ilford explains exactly what to do.

For Thornton's 2-Bath developer, Pictorial Planet says that 1 L will process 15 rolls, so I'm going to assume that 500 mL will process 7 rolls.

The concept of use for multiple rolls with single developer is that all the rolls would be processed in a relatively short time...all in one day, maybe within 2-3 days...used developer simply is not intended to be stored like periodic use by an amateur hobbyist! You store 'stock' solution, to be later diluted for use; and you throw out 'working solution' after each use. Some developers can be 'replenished' to do multiple rolls with the same solution in a single darkroom session.
So if you plan on a few rolls one week, then a few more rolls in another week, you are best served with one-shot usage...process a roll (or whatever capacity of rolls per liter of mixed developer at usage strength), and throw out the developer.

Hunter_Compton · May 30, 2025

wiltw said:
The concept of use for multiple rolls with single developer is that all the rolls would be processed in a relatively short time...all in one day, maybe within 2-3 days...used developer simply is not intended to be stored like periodic use by an amateur hobbyist! You store 'stock' solution, to be later diluted for use; and you throw out 'working solution' after each use. Some developers can be 'replenished' to do multiple rolls with the same solution in a single darkroom session.
So if you plan on a few rolls one week, then a few more rolls in another week, you are best served with one-shot usage...process a roll (or whatever capacity of rolls per liter of mixed developer at usage strength), and throw out the developer.

It depends on the developer in question, for example the datasheet for Kodak T-Max developer says that the working strength solution can be kept in tightly capped full bottles for six months.

I've had no issue keeping it in glass bottles and using it over a period of months until it's useful capacity is diminished.

https://business.kodakmoments.com/sites/default/files/files/resources/j86.pdf

Bill Burk · May 30, 2025

dcy said:
My Patterson tank says that each roll requires 290 mL.

Those are English ml

Actually just said that to be funny because my Paterson beaker has scales on two sides, I have to be careful not to look at the English fl.oz. instead of the U.S. Fluid Ounces side.

Point being. Always use more fluid in a Paterson tank than they say, that may help you avoid bubbles that show as swirling edges on your negatives. Rap that tank when agitating to dislodge bubbles.

dcy · May 30, 2025

wiltw said:
The concept of use for multiple rolls with single developer is that all the rolls would be processed in a relatively short time...all in one day, maybe within 2-3 days...used developer simply is not intended to be stored like periodic use by an amateur hobbyist! You store 'stock' solution, to be later diluted for use; and you throw out 'working solution' after each use.

Does the stock solution go bad faster if you've used it to develop film?

wiltw said:
So if you plan on a few rolls one week, then a few more rolls in another week, you are best served with one-shot usage...process a roll (or whatever capacity of rolls per liter of mixed developer at usage strength), and throw out the developer.

Ok. I know how to one-shot D-76 and D-23 (i.e. dilute them 1+1).

But can you one-shot 2 bath developers like Thornton or Divided D-23? ... I mean... They work by soaking up the developer in Part A. It doesn't sound to me like you can just dilute those developers.

EDIT:
Considering that very little development takes place in Part A, would you agree that 2-Bath developers are an exception to the rule, and I can basically just keep using Part A for as long as I have enough of it left to cover the film? Part A is comparable to stock D-23, so I imagine it'll last about as long as stock D-23.

Furthermore, I would guess that you can ignore the age of Part B as well. Part B is just supposed to be alkaline. If the small amount of developer that got into Part B gets exhausted, that'd just make Part B behave better. So if I follow @relistan 's recommendation and replace Part B based on how many rolls have gone through it, then I should be fine.

Right?

john_s · May 30, 2025

dcy said:
Does the stock solution go bad faster if you've used it to develop film?

.......

The instructions for an Agfa standard film developer stated that the working solution could be reused as long as it was with a certain time period (maybe a week or two?) so I would guess that the answer to your question is "yes."

Paul Howell · May 30, 2025

I have been using up my stash of old chemistry, Acufine, DK 50, and Diafine. Once these are gone I will return to HC or Clayton F76+ as I don't shoot enough rolls for economical use of D76. With HC (HC 110) ILford Tech HC, or Clayon F76+ one shot and done. And remember it is not only how many rolls how how long the developer has been mixed.

Raghu Kuvempunagar · May 30, 2025

dcy said:
Considering that very little development takes place in Part A,

This is not true. In Thornton's Two Bath developer, substantial development does take place in the first bath.

wiltw · May 31, 2025

dcy said:
Does the stock solution go bad faster if you've used it to develop film?

Ok. I know how to one-shot D-76 and D-23 (i.e. dilute them 1+1).

But can you one-shot 2 bath developers like Thornton or Divided D-23? ... I mean... They work by soaking up the developer in Part A. It doesn't sound to me like you can just dilute those developers.

EDIT:
Considering that very little development takes place in Part A, would you agree that 2-Bath developers are an exception to the rule, and I can basically just keep using Part A for as long as I have enough of it left to cover the film? Part A is comparable to stock D-23, so I imagine it'll last about as long as stock D-23.

Furthermore, I would guess that you can ignore the age of Part B as well. Part B is just supposed to be alkaline. If the small amount of developer that got into Part B gets exhausted, that'd just make Part B behave better. So if I follow @relistan 's recommendation and replace Part B based on how many rolls have gone through it, then I should be fine.

Right?

The answers to your questions is once again, "It depends" ...upon which developer you are asking about! Storage is generally discussed in the directions for use.

How do you know when to stop reusing a developer?

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