Estimating the expected life time of developer

Raghu Kuvempunagar · Mar 31, 2019

Is it possible to estimate (approximately) the expected life time of a developer concentrate or reusable developer solution (like Adox MQ Borax 1+0) stored in a specific container (say a thick HDPE bottle) at a specific temperature (say 25C) by doing some simple experiments? Say I store the developer (concentrate or 1+0 solution) in a bottle at 25C. I might want to know how long will it be fully active. Without having to wait for another six months, are there some tests that I can do today to get an approximate answer?

One possible line of attack is to leverage the relationship between rate of reaction and temperature. How about keeping the bottle in a water bath maintained at 75C for a day (or a week) and then checking the potency of the solution? Using the formula*** exp(0.081*(t-25))*n where t is the water bath temperature and n is the number of days in the water bath, and substituting t with 75 and n with 1, one gets 57 days. So if the solution survived for a day in the water bath, it is equivalent to surviving approximately two months in normal condition. Would something like this make sense? Or is there a better way?

*** The formula is for HC-110 and borrowed from http://www.covingtoninnovations.com/hc110/. It might not hold for other developers as noted by Alan below.

Rick A · Mar 31, 2019

Why would you want to store developer diluted to working strength? It's meant to be diluted just prior to use then discarded when finished.

Ian C · Mar 31, 2019

I’ve solved the problem of developer life using the following strategy:

I first determine the total film-developing capacity of the volume of developer I need. I WAIT until I have that much exposed film. Only then do I mix fresh developer, use it to capacity, and then discard the exhausted developer. In this way there is no waste. All films are correctly processed in fresh, strong developer, and I got the full developing capacity of the chemicals.

Raghu Kuvempunagar · Mar 31, 2019

Rick A said:
Why would you want to store developer diluted to working strength? It's meant to be diluted just prior to use then discarded when finished.

You're right, but I actually meant stuff like reusable developer solutions like Adox MQ Borax 1+0.

Rick A · Mar 31, 2019

By 1+0 o you mean stock solution. Most, if not all, manufacturers list shelf life of their products in the supplied literature. Reusable developers is purely subjective, variable by open time, actual use, storage container, temps, etc. Is there a way to predict failure? Who knows. I use a replenishable paper developer, Ethol LPD, my room temps range from 65f in winter to around 75f in summer, my current batch is going on three years for stock, ongoing replenishment to working strength. My original batch started some 17 or 18 years ago, and 5 packages of powder since starting. It's been ongoing with no dumping due to expiration.I mix a fresh batch of stock developer when I'm down to my last liter, and keep replenishing.

faberryman · Mar 31, 2019

I solved the problem too. If I have spent money on a roll of film, and spent valuable time taking photographs, if there is any doubt in my mind, I prepare fresh developer. If in doubt, throw it out. Using one shot developer mixed from a concentrate purchased in a quantity reasonable for my anticipated needs makes the procedure easy to implement.

bernard_L · Mar 31, 2019

Raghu Kuvempunagar said:
say a thick HDPE bottle

Not! HDPE will leak atmospheric oxygen into your solution. And AFAIK there is no reliable temperature scaling to validate accelerated ageing. If you use a glass bottle with an air-tight closure or a wine pouch with suitable oxygen barrier, you will not know in advance the lifetime of your developer, but it will definitely last longer. What is most important for you?

Low tech solution, no equipment needed. Expose a series of frames of uniform surface at metered exposure (uniformity and consistency are critical, actual value not so much). Keep the film in a light tight box. Develop one frame (does not matter if you cut across frame) with fresh dev and before each development of important film. Dev exhaustion from that experiment is minimal, so even one-shot can be re-used. Compare visually with "fresh-dev" frame. If you see no difference, all is OK.

MattKing · Mar 31, 2019

bernard_L said:
Low tech solution, no equipment needed. Expose a series of frames of uniform surface at metered exposure (uniformity and consistency are critical, actual value not so much). Keep the film in a light tight box. Develop one frame (does not matter if you cut across frame) with fresh dev and before each development of important film. Dev exhaustion from that experiment is minimal, so even one-shot can be re-used. Compare visually with "fresh-dev" frame. If you see no difference, all is OK.

Make sure you don't use Pan F+ for this.
Latent image retention failure could affect your results.

pentaxuser · Mar 31, 2019

OP such a solution would be great if there is a formula that reliably predicts the expected life. If you find one and evidence of its proven reliability let us know.A fairly reliable solution would be to do nothing until you have reached the manufacturer's storage limits which are very conservative then employ the film leader test. Once you have established from that what your own storage conditions give you for that particular developer then you should be able to rely on that at least until close the limits already established and then use the leader test.

For what it is worth I keep Xtol stock in winebags and on two occasions I have noted that from the first time the concentrate comes out even as a very pale straw colour the film will still develop but not as it should, I.e. in a dire emergency of having to develop a film and not being able to wait for fresh Xtol powder I would be able to use it but I know that the resulting negatives will be second best. So a pale straw colour is my signal for dumping the Xtol

pentaxuser

MattKing · Mar 31, 2019

pentaxuser said:
For what it is worth I keep Xtol stock in winebags and on two occasions I have noted that from the first time the concentrate comes out even as a very pale straw colour the film will still develop but not as it should, I.e. in a dire emergency of having to develop a film and not being able to wait for fresh Xtol powder I would be able to use it but I know that the resulting negatives will be second best. So a pale straw colour is my signal for dumping the Xtol

pentaxuser

Also for what it is worth, I believe that pentaxuser's post is the first and only example I have ever seen of someone who has been able to see a change in the appearance of XTol at the time it goes "bad".
The (now almost) universal opinion is that XTol gives no visual clues when it loses activity.

Alan Johnson · Mar 31, 2019

There is a fundamental flaw in the argument in post 1 - it assumes that the temperature coefficient , commonly referred to as Q10 is the same for all reactions.
To do an accurate test it would be needed to know both the reaction referred to and its Q10.
For a rough estimate guessing Q10 = 2 might do., the rate then doubles for every 10C temperature rise.
http://clay6.com/qa/94538/the-tempe...-reaction-is-2-and-the-rate-of-reaction-at-25

pentaxuser · Mar 31, 2019

MattKing said:
Also for what it is worth, I believe that pentaxuser's post is the first and only example I have ever seen of someone who has been able to see a change in the appearance of XTol at the time it goes "bad".
The (now almost) universal opinion is that XTol gives no visual clues when it loses activity.

Yes, Matt, on both occasions it has been reliable. Users have to look closely at the concentrate stock and compare it to the colour of water, literally, which Xtol replicates while it is fresh in my experience. Once you dilute it to 1+1 it returns closely enough to the colour of water to fool my eye at least. The proof on both occasions has been the leader test which reveals that a leader in fresh Xtol against the light of day compared to a leader developed in pale straw coloured Xtol is different. My normal comparison with the wire in an incandescent bulb is such that the additional dimness of the wire from fresh Xtol can still be difficult to detect. However looking through both leaders against a relatively bright daylight scene does reveal a difference that most users could detect. It may well be that those whose perception of a slight difference in dimness against an incandescent wire in a bulb is better than mine would not the daylight test of looking through both leaders at a bright daylight scene

pentaxuser

MattKing · Mar 31, 2019

pentaxuser said:
Yes, Matt, on both occasions it has been reliable. Users have to look closely at the concentrate stock and compare it to the colour of water, literally, which Xtol replicates while it is fresh in my experience. Once you dilute it to 1+1 it returns closely enough to the colour of water to fool my eye at least. The proof on both occasions has been the leader test which reveals that a leader in fresh Xtol against the light of day compared to a leader developed in pale straw coloured Xtol is different. My normal comparison with the wire in an incandescent bulb is such that the additional dimness of the wire from fresh Xtol can still be difficult to detect. However looking through both leaders against a relatively bright daylight scene does reveal a difference that most users could detect. It may well be that those whose perception of a slight difference in dimness against an incandescent wire in a bulb is better than mine would not the daylight test of looking through both leaders at a bright daylight scene

pentaxuser

I believe we have a false equivalency here
I do not doubt that your spent X-Tol may have a slight colour to it.
The problem being that most examples of spent X-Tol do not display any such colour.
And that there are probably examples out there where straw coloured X-Tol hasn't yet died.

mshchem · Mar 31, 2019

MattKing said:
And that there are probably examples out there where straw coloured X-Tol hasn't yet died.

https://www.photrio.com/forum/threads/xtol-11-year-old-stock-solution-worked.146101/

I think XTOL sudden death is due to bad Karma .

mshchem · Mar 31, 2019

Raghu Kuvempunagar said:
Is it possible to estimate (approximately) the expected life time of a developer concentrate or reusable developer solution (like Adox MQ Borax 1+0) stored in a specific container (say a thick HDPE bottle) at a specific temperature (say 25C) by doing some simple experiments? Say I store the developer (concentrate or 1+0 solution) in a bottle at 25C. I might want to know how long will it be fully active. Without having to wait for another six months, are there some tests that I can do today to get an approximate answer?

How about keeping the bottle in a water bath maintained at 75C for a day (or a week) and checking the potency of the solution? Using the formula exp(0.081*(t-25))*n where t is the water bath temperature and n is the number of days in the water bath, and substituting t with 75 and n with 1, one gets 57 days. So if the solution survived for 7 days in the water bath, it is equivalent to surviving approximately two months in normal condition. Would something like this make sense? Or is there a better way?

Accelerated life testing is done to find weaknesses in design . Running equipment in heat, dirt, corrosive conditions. Not sure if you could get the formula you are after without some extensive testing. Until then follow the instructions from Adox.

Raghu Kuvempunagar · Mar 31, 2019

Alan Johnson said:
There is a fundamental flaw in the argument in post 1 - it assumes that the temperature coefficient , commonly referred to as Q10 is the same for all reactions.
To do an accurate test it would be needed to know both the reaction referred to and its Q10.
For a rough estimate guessing Q10 = 2 might do., the rate then doubles for every 10C temperature rise.
http://clay6.com/qa/94538/the-tempe...-reaction-is-2-and-the-rate-of-reaction-at-25

The formula I used is for HC-110 and borrowed from http://www.covingtoninnovations.com/hc110/. The same web-page says this:
"Though derived from published data about HC-110, these formulae are also approximately correct for most other developers."

Raghu Kuvempunagar · Apr 1, 2019

mshchem said:
Accelerated life testing is done to find weaknesses in design .

This is indeed the line of study I was interested in knowing more about. Accelerated life testing. Found an interesting survey: https://arxiv.org/pdf/0708.0369.pdf. Thanks a lot!

mshchem · Apr 1, 2019

Raghu Kuvempunagar said:
This is indeed the line of study I was interested in knowing more about. Accelerated life testing. Found an interesting survey: https://arxiv.org/pdf/0708.0369.pdf. Thanks a lot!

This looks like a great project. Very interesting information.
Best Regards Mike

Alan Johnson · Apr 1, 2019

Raghu Kuvempunagar said:
The formula I used is for HC-110 and borrowed from http://www.covingtoninnovations.com/hc110/. The same web-page says this:
"Though derived from published data about HC-110, these formulae are also approximately correct for most other developers."

This formula is for the effect of temperature on the development time of films over small temperature changes 19-25 C according to the linked article, not for loss of activity due to hydrolysis or oxidation.over a large temperature range.
The OP does not make clear how much air is allowed in the bottle, If none the question refers to loss of activity due to hydrolysis, if the bottle is regularly opened the oxidation will presumably proceed at an ever increasing rate as the volume of air compared to that of developer increases.The limiting cases are if the bottle is kept fully stoppered and full the whole time or if it is left completely open to the air.An intermediate case would be to guess conservatively the practise of the average user in opening the bottle.
The question is not very clear.

Raghu Kuvempunagar · Apr 1, 2019

Alan Johnson said:
The OP does not make clear how much air is allowed in the bottle, If none the question refers to loss of activity due to hydrolysis, if the bottle is regularly opened the oxidation will presumably proceed at an ever increasing rate as the volume of air compared to that of developer increases.The limiting cases are if the bottle is kept fully stoppered and full the whole time or if it is left completely open to the air.An intermediate case would be to guess conservatively the practise of the average user in opening the bottle.
The question is not very clear.

Alan, approximate solutions for any of the scenarios described by you are interesting to me. When researchers and practitioners develop new developer formula, they would want to know the expected lifetime of the developer in a small number of representative scenarios without having to rely on father time to tell the answer. Similarly when hobbyists brew a developer at home using a formula found on this site, there's no manufacturer datasheet to help them on expected lifetime. Some way of accelerated testing is desirable.

pentaxuser · Apr 1, 2019

MattKing said:
I believe we have a false equivalency here
I do not doubt that your spent X-Tol may have a slight colour to it.
The problem being that most examples of spent X-Tol do not display any such colour.
And that there are probably examples out there where straw coloured X-Tol hasn't yet died.

Matt, I cannot deny anything you say as my data only includes two tests so statistically it is way off being even close to statistically significant . I have little doubt that my straw coloured Xtol would have produced usable negs, as I said, but in my case I am pretty sure not the best negs. The next leader in fresh( newly mixed) Xtol was darker. My fear and this may not be others' fear is if I were to use the straw-coloured Xtol then I will not be able to detect when straw-coloured Xtol does become useless. It may go darker as a sign or may stay the same or change very marginally and still be exhausted.

At that stage and in the case of my Xtol on both occasions, it was over 2 years old. In fact 3 years one month in the latest case so I regard the straw coloured signal combined with age as a reliable sign or reliable enough on the "why risk it" basis.

pentaxuser

trendland · Apr 1, 2019

Raghu Kuvempunagar said:
Is it possible to estimate (approximately) the expected life time of a developer concentrate or reusable developer solution (like Adox MQ Borax 1+0) stored in a specific container (say a thick HDPE bottle) at a specific temperature (say 25C) by doing some simple experiments? Say I store the developer (concentrate or 1+0 solution) in a bottle at 25C. I might want to know how long will it be fully active. Without having to wait for another six months, are there some tests that I can do today to get an approximate answer?

One possible line of attack is to leverage the relationship between rate of reaction and temperature. How about keeping the bottle in a water bath maintained at 75C for a day (or a week) and then checking the potency of the solution? Using the formula*** exp(0.081*(t-25))*n where t is the water bath temperature and n is the number of days in the water bath, and substituting t with 75 and n with 1, one gets 57 days. So if the solution survived for a day in the water bath, it is equivalent to surviving approximately two months in normal condition. Would something like this make sense? Or is there a better way?

*** The formula is for HC-110 and borrowed from http://www.covingtoninnovations.com/hc110/. It might not hold for other developers as noted by Alan below.

That all you stated would be good and interisting to find out via experiment!
But you can not estimate interactions of different chems from a model what is based on a paradigma of linear functions! 1) you have allways a log. function 2) interaction of chems
can have a more chaotic pattern!
They interact from strong rules of course - but changing all kind of parameter will give no math prove of livetime wich is nearly exact! It seams to be it is possible to show from a couple of additional experimental datas weithin a Matrix ! But this Matrix if it should be most precise would contain all kind of datas wich are proved experimental.
Two things you are well knowing : 1) the weather forecast isn't little precise one week in advance!
2) at -273 Celsius you may store your developer concentrate more than 100.000 years and it should be quite OK after defreezing it!

with regards

PS : What about to store the raws?

trendland · Apr 1, 2019

[QUOTE="Raghu Kuve
Using the formula*** exp(0.081*(t-25))*n [/QUOTE]

Is this your formula?

with regards

Alan Johnson · Apr 2, 2019

Raghu Kuvempunagar said:
Alan, approximate solutions for any of the scenarios described by you are interesting to me. When researchers and practitioners develop new developer formula, they would want to know the expected lifetime of the developer in a small number of representative scenarios without having to rely on father time to tell the answer. Similarly when hobbyists brew a developer at home using a formula found on this site, there's no manufacturer datasheet to help them on expected lifetime. Some way of accelerated testing is desirable.

Raghu,
I think this could work for the cases of full sealed bottle and bottle open to the air.
For the intermediate case, simulating actual use with regular opening of the bottle and removing some of its developer content each time, it would also be needed to decide on some standard protocol for this.
For 75C an oil bath seems preferable to a water bath. The formula given in post 11 link could be used.
It looks to me that this would be a procedure for a manufacturer rather than a hobbyist, but they might prefer just to make an educated guess.

Estimating the expected life time of developer

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