Would I be missing anything if I use D-23 instead of D-76?

Yezishu said:

Assuming a 135 film contains 0.3g of silver, with 25% being developed, this would consume 0.12g of Metol (sulfate).
Using 250ml D-23 developer, which contains 1.875g of Metol, the consumption rate is 6.4%.
If using 250ml D-23 diluted 1:1, containing 0.9375g of Metol, the consumption rate rises to 12.8%.

If someone wants the fluctuation in Metol concentration within 7.5% (a very subjective assumption) , more 1:1 developer solution should be used.
There are similar calculations regarding bromide as well.

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So on your calculations shown above, how many 35mm films can the 7.5 g of metol in 1L of D23 develop if used at 1:1 and how does the need for 100g of sulfite change things?

Did you mean sulfite when you mention bromide

Thanks

pentaxuser

pentaxuser said:

Thanks for sharing what you do but I was only speculating as to why John Finch did not mention in his video the option of scaling down his 1L

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I didn't mean to hijack your train of thought. I was just chatting.

pentaxuser said:

What I found useful in darkroommike's reply was that D23 has the added attraction of being scaled down. I am no photographic chemist but I suspect that not all developers lend themselves to straightforward "scaling down as some may need a minimum amount of certain ingredients to be effective

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Yeah. For example, I could imagine that a very dilute developer might behave very differently if it's scaled down. Maybe 6 mL of Rodinal in 300 mL water is not the same as 12 mL of Rodinal in 600 mL of water.

pentaxuser said:

darkroommike, nice to know that this can be done even down to an amount for 1x35mm film in a Jobo tank of only 250mm John Finch briefly mentions scaling down to 500ml in response to a question from a viewer of the video but I suspect that he doesn't mention any further scaling down as you lose the simplicity of the "teaspoon" method and D23's keeping qualities means that the usual 1L can still be used within the likely time you'd develop 4 x 35mm films of 2x120 films

pentaxuser

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I usually don't use the teaspoon method but when I do I have one set of dedicated spoons that I use exclusively in the darkroom. 3grams of Metol is 1 teaspoon, that's 2.5 teaspoons for a liter. And 100 grams of anhydrous sodium sulfite is 12 2/3 teaspoons, or 4 Tablespoons and 2/3 teaspoon. It's hardly any more work to just get a small digital scale.

As far as the capacity of a liter of working solution MQ developers, D23 or D76 for example, Kodak ran the numbers and that their recommended capacities per liter are good (and probably very conservative, but capable of delivering pretty consistent results). My old Darkroom Dataguide (1974, Brown Cover) lists the capacity of D-76 as 16 8x10/rolls per gallon, or about 4 rolls (80 sq. in.) per liter. If you diluted you stock 1+1 you could process each of those rolls in fresh developer discarding after one use. A tank of replenished developer can process twice as many films using 1 unit of developer with an equal volume of replenisher. TANSTAAFL. You can and I did when I was a young, broke, college lad run twice as much film in that much developer with a tiny tradeoff in quality. I often ran two rolls of 135-36 in a 500mL tank with D-76 1:1 rather than just one roll.

pentaxuser said:

So on your calculations shown above, how many 35mm films can the 7.5 g of metol in 1L of D23 develop if used at 1:1 and how does the need for 100g of sulfite change things?

Did you mean sulfite when you mention bromide

Thanks

pentaxuser

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Please allow me to make a rough calculation.

with 7.5g Metol, we can prepare 2L D23 at a 1:1 dilution. Assume that each roll of film consumes 0.12g of Metol.

(1) If we divide the 2L solution into four portions of 500ml and each containing 1.875g of Metol, and use each portion for a single roll:
Then, the Metol concentration for each roll would decrease from 100% to 93.6% (a 6.4% reduction).

(2) Or, if we use a single 2L tank to develop four rolls consecutively, the concentration would decrease by 1.6% with each roll:
First roll: 100% → 98.4%
Second roll: 98.4% → 96.8%
Third roll: 96.8% → 95.2%
Fourth roll: 95.2% → 93.6%
Although the concentration change per roll is small, the cumulative effect might be significant. Some instructions recommend increasing development time after a certain number of rolls to compensate.

The real question is: If the Metol concentration drops from 100% to 93.6% over the 10 minutes of developing a single roll, or from 95.2% to 93.6%, which approach yields better photo, or more acceptable? Actual density curve measurements maybe needed for comparison.

(3) If we consider replenishment, we can use 3.75g of Metol to prepare 1L of D23 at 1:1 dilution.
The first roll consumes 0.12g, reducing the concentration from 100% to 96.8%. Afterward, adding 0.12g of Metol restores the concentration to 100%.
With the remaining 3.75g Metol, you can develop approximately 31 rolls in total, and for each roll, the concentration only drops from 100% to 96.8%—a relatively small change than in (1) & (2).
Replenishment method is popular (and much more economical) in industrial settings.

----------The above only considers changes in Metol concentration.

Regarding bromides: assuming the film mainly contains silver bromide, development not only produces silver but also generates hydrobromic acid. Bromide ions inhibit development, while the hydrogen ions are typically neutralized by the buffer, for example, reacting with sulfite to form bisulfite.

This leads to issues similar to Metol depletion:
1. The concentration of bromide ions increases with development, slowing down the development rate.
2. The pH of the solution drops during development, also slowing down the process.
Additionally, due to handling, the solution inevitably comes into contact with air, so we must also consider:
3. Sodium sulfite in the solution is oxidized and consumed by air in long time operation, causing other issues.

Often, these changes are minor enough to be ignored, but if you need to develop 31 rolls continuously within 1L solution, all these factors should be considered. Typically, some solution (along with the reduced product of Metol, bromides and bisulfite) is discarded or carried away with the film, and replenisher is added with water, Metol, and sodium sulfite to maintain solution stability. Like this...

Donald Qualls said:

but not CD-4, says the bottle I had that turned green in the sealed bottle

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That's odd. CD4 is very stable when stored dry. When it degrades, it goes very deep purple, virtually black - not green.

koraks said:

When it degrades, it goes very deep purple, virtually black - not green.

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It's been a few years since I dug it up from my shed. It had spent at least a couple winters and summers there (well below freezing on winter nights, above 100F in the shed on summer days). It may have been only partly degraded, but the solution was definitely green, not the straw color it should have been, when I tried to mix the C-41 two-bath developer I'd used in the past.

Hm, odd, never seen that happen!

koraks said:

That's odd. CD4 is very stable when stored dry. When it degrades, it goes very deep purple, virtually black - not green.

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A off-topic question: Have you ever seen CD4 display a nice pink color in solution? Do its degrade products in solution tend to show this change(like, pink->dark pink->purple)? I observed pink color in acidic solutions(not developer) containing CD4, but I’m not sure whether CD4 is actually involved in the reaction or not, I remember that used C41 developer solution maybe brown?

Yezishu said:

Have you ever seen CD4 display a nice pink color in solution?

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Yes, CD4 is magenta in solution as soon as it oxidizes. The brown coloration of used C41 developer is due to a mix of oxidation products and various dyes that wash out of the film during processing. But if you take some water and only dissolve a little CD4 in it, this will go a very pretty shade of pink.

koraks said:

Yes, CD4 is magenta in solution as soon as it oxidizes. The brown coloration of used C41 developer is due to a mix of oxidation products and various dyes that wash out of the film during processing. But if you take some water and only dissolve a little CD4 in it, this will go a very pretty shade of pink.

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Thank you for your answer and experience!

Yezishu said:

Assuming a 135 film contains 0.3g of silver, with 25% being developed, this would consume 0.12g of Metol (sulfate).

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Based on this assumption which was also used in another thread about re-using developer where the 0.12g was not challenged and if my maths are correct the 7.5 g of Metol will develop about 62 films - an amazing figure

So if for the sake of getting the maximum out of the chemical Metol you were to try developing one film at a time with 0.12g of Metol, what might be the correct quantity of Sulfite for each film? Is that simply a question of dividing 100g of sulfite as well or is the sulfite figure different In other words what be the limit of scaling down each chemical in order to develop one film only?

Yes I appreciate this may not be worthwhile in terms of time and effort etc but sticking to what the logic states of 0.12g of Metol per film seems to say and my education in terms of chemistry in photography I'd appreciate a "what if" sort of discussion

Thanks

pentaxuser

pentaxuser said:

So if for the sake of getting the maximum out of the chemical Metol you were to try developing one film at a time with 0.12g of Metol, what might be the correct quantity of Sulfite for each film? Is that simply a question of dividing 100g of sulfite as well or is the sulfite figure different In other words what be the limit of scaling down each chemical in order to develop one film only?

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It's an unanswerable question, because in practice, it's not possible to develop a film with 120mg of Metol, because there's no way to get that exact amount of Metol exactly where it needs to be, when it needs to be there. Since the amount of sulfite depends on factors that relate to the actual dynamics of development, and these dynamics we cannot know (because they basically cannot exist), the question is moot.

pentaxuser said:

I'd appreciate a "what if" sort of discussion

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Lacking an 'if', there cannot be a 'what'.

pentaxuser said:

Based on this assumption which was also used in another thread about re-using developer where the 0.12g was not challenged and if my maths are correct the 7.5 g of Metol will develop about 62 films - an amazing figure

So if for the sake of getting the maximum out of the chemical Metol you were to try developing one film at a time with 0.12g of Metol, what might be the correct quantity of Sulfite for each film? Is that simply a question of dividing 100g of sulfite as well or is the sulfite figure different In other words what be the limit of scaling down each chemical in order to develop one film only?

Yes I appreciate this may not be worthwhile in terms of time and effort etc but sticking to what the logic states of 0.12g of Metol per film seems to say and my education in terms of chemistry in photography I'd appreciate a "what if" sort of discussion

Thanks

pentaxuser

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The industrial method involves preparing a tank of solution as a buffer. After each roll is developed, a small amount of replenisher with a little Metol is added.
Those who use the Xtol replenishment method report similar results: by adding 70 ml of replenisher each time, 4 L replenisher can process about 57 rolls. Considering that some unused developer will lost with film (about 20 ml) and discarded solution (about 50 ml) after each roll, the utilization is far from 100%, but it is still substantial.
But if you mean only 0.12g of Metol, not added 0.12g each time, I don't know how to do it, or even if it is possible.......

I think about it again.
If you consider "using the minimum amount of developer," I would guess this refers to some highly dilutable developers, such as 6ml Rodinal for a roll (1:100).
Or if you mean "the least amount of specialized chemicals," then Phenidone would be the winner—a few milligrams of Phenidone combined with vitamin C and sodium carbonate are enough to develop a roll of film.

In short, I did some calculations. The 1L Rodinal uses about 10–20g of p-Aminophenol Hydrochloride; let’s assume 15g. To reduce 25% of the 0.3g of silver in a roll, we need 0.038g of p-Aminophenol Hydrochloride, equivalent to 2.53ml of Rodinal.

The usual recommendation is at least 6ml of concentrate (diluted 1:50 to make 300ml) per roll, which uses about 0.09g of p-Aminophenol Hydrochloride—close to the calculated requirement. Similar ideas may meet @pentaxuser 's need to use minimum amount of chemicals.

The key may be to use a strong alkali to raise the pH above 11, even when highly diluted, so the developer remains active. Sufficient time and agitation are also important to ensure fully reaction. However, it must be highly different from D-23.......

Thanks for all the answers, Yezishu and koraks. It was simply the statement made by Yezishu that seemed to indicate that one film could be developed fully and properly by 0.12g of Metol. The logical extension of this is that 62 films can be developed by 7.5 grams

In terms of practicality I thought there were now relatively cheap digital scales that measure down to three figures of decimals which led me on to wonder what might be issues with the second chemical of sulfite. Could that be scaled down in a similar fashion. Hence the "what if"

Call asking "what if " questions a sign of troublesome schoolboy naivety but such questions may lead to the experts who are more knowledgeable by definition, deciding to try giving an explanation to the less knowledgeable pupil aimed at the latter's level of knowledge

Turning now to the specifics of the answers from yourself, koraks

"It's an unanswerable question, because in practice, it's not possible to develop a film with 120mg of Metol, because there's no way to get that exact amount of Metol exactly where it needs to be, when it needs to be there".

Why is it not possible to get that amount of Metol (0.12g) exactly where it needs to be? It has been distributed in the water which in turn will cover the whole film and in the course of several minutes agitation surely makes contact with the whole area of the film ? So what am I missing ?

"Since the amount of sulfite depends on factors that relate to the actual dynamics of development, and these dynamics we cannot know (because they basically cannot exist), the question is moot.

I am completely puzzled by this answer. What is it about the dynamics of development that we cannot know because they cannot exist. What does the word "exist" refer to? Surely the dynamics of development exist: so do they change in a random fashion each time we develop a film such that even if we were able to analyse the dynamics on any particular development those dynamics would not exist in that form the next time?

Maybe the simple answer is that scaling down each ingredient works down to a certain amount but nobody know what the limit is? We know we can cut the ingredients by 50% when using 500ml of D23 so can we safely cut the ingredients by another 50% if we only need to develop one 35mm film needing only 250ml?

Where can we go with scaling down the ingredients? If 140ml of water is the irreducible minimum of water with a 35mm film do we know what changes occur or do not occur if we cut the ingredients proportionately to 140 over 250ml?

All I am trying to do is ask open questions from first principles to see where it leads to gain a greater understanding


Thanks

pentaxuser

pentaxuser said:

In terms of practicality I thought there were now relatively cheap digital scales that measure down to three figures of decimals

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There are. You have described my cheap there-decimal-figure scale exactly. My scale currently retails on Amazon for $17 and it has 0.001g accuracy and two 20g weights to both test its calibration and improve its accuracy (scales are most accurate near the middle of their weight range).

pentaxuser said:

Maybe the simple answer is that scaling down each ingredient works down to a certain amount but nobody know what the limit is? We know we can cut the ingredients by 50% when using 500ml of D23 so can we safely cut the ingredients by another 50% if we only need to develop one 35mm film needing only 250ml?

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Since the issue at hand is how to get the Metol to the silver halide grains that need it, I imagine that you can push the limit further with more agitation and by maximizing the fraction of the solution that is in contact with the film. To do the latter, you'd want to decrease the water volume and spread the solution thinly on top of the film ---- i.e. either develop on a tray like sheet film, or in a rotary processor.

pentaxuser said:

All I am trying to do is ask open questions from first principles to see where it leads to gain a greater understanding

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My take is that you don't need to justify anything. It's a hobby. These questions don't need to be a means to an end. "I'm curious" is a good enough reason.

pentaxuser said:

It has been distributed in the water which in turn will cover the whole film and in the course of several minutes agitation surely makes contact with the whole area of the film ?

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Tell me how much water that would be and how long it'll take to get the 120mg of metol to every exposed silver grain, without contributing to fog. Once you've worked out that answer, you'll understand that the time is infinite and the result is that some of the metol will be wasted on producing non-image fog, so the experiment fails.

That's also what the 'cannot exist' refers to. The thought experiment you've designed is just that; it doesn't stand the test of practical feasibility. Sulfite is there at least in part to protect the metol against oxidation, which depends on agitation, duration of development etc. Under normal conditions, these factors will not be very significant, but since our development time here is effectively infinite, we have to take into account that all the sulfite will oxidize and turn into sulfate, which coincidentally renders the developer less active (D76) or completely inactive (D23). Which again contributes to problem of a long development time, which we have established to be infinite to begin with.

Koraks pointed out several obvious issues.

First, how to accurately deliver Metol into the emulsion? Without sufficient volume, proper mixing and even diffusion are impossible. Even with rotary processing, a minimum amount of liquid is still required. As mentioned before, the film and reel alone can absorb around 20ml, so the developer volume must be higher, with adequate concentrations of sodium sulfite and/or pH adjusters. People replicating Polaroid films or using monobath might have better advice on minimum volumes per roll, but as far as I know, they use much higher developer concentrations.

Second, in dynamics, is the Metol concentration too low for development to start effectively? Even if it can, as Metol is quickly depleted, the reaction will slow dramatically. For low concentration of Metol to react fully, the solution needs to be highly alkaline and highly reactive, which could cause unwanted oxidation—either by air or by unexposed silver halide which leading to fog. This is likely the reason why Rodinal not use Metol. Very small amounts of strong alkali sodium sulfite solution are also unstable due to O₂/CO₂ absorption. Taking these into account, I think it’s always need more than the calculated minimum amount. These issues would not occur with a higher concentration of Metol.

And after those changes, this formula maybe nothing like D23—apart from Metol. Maybe you can consider try diluting 3ml of Rodinal to 150ml to develop a roll, then try 1 ml to 50 ml, and observe what happens at such a small amount.

I've been pondering the question posed in the title of this thread (Would I be missing anything if I use D-23 instead of D-76?). It almost boils down to 'What did hydroquinone ever do for us?'

My experience of metol-only development is chiefly with Thornton's 2-bath formula. For the vast majority of scenes, I get negatives that print straight or with minimal manipulation on grade 2 or 2 1/2 (Ilford Multigrade Classic). If they don't, it's usually because I have cocked-up the exposure. So why would I need more contrast? If I was routinely having to use grade 3 or higher, I might understand, but that's not the case.

snusmumriken said:

I've been pondering the question posed in the title of this thread (Would I be missing anything if I use D-23 instead of D-76?). It almost boils down to 'What did hydroquinone ever do for us?'

My experience of metol-only development is chiefly with Thornton's 2-bath formula. For the vast majority of scenes, I get negatives that print straight or with minimal manipulation on grade 2 or 2 1/2 (Ilford Multigrade Classic). If they don't, it's usually because I have cocked-up the exposure. So why would I need more contrast? If I was routinely having to use grade 3 or higher, I might understand, but that's not the case.

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That's a big oversimplification. Superadditivity is not necessarily about contrast, although it is in some cases. It's about other aspects of sensitometry, image structure characteristics, capacity/stability etc.

The D-23 / D-76 comparison should really be considered a special case in that they are metol-based solvent developers, and that D-23 was formulated to perform very similarly to D-76. Generalizing too far beyond that is problematic.

On the other hand from a broader practical perspective the differences among developers are often greatly exaggerated, so one could reasonably ask would I be missing anything if I use D-23 instead of [insert many alternatives].

snusmumriken said:

I've been pondering the question posed in the title of this thread (Would I be missing anything if I use D-23 instead of D-76?). It almost boils down to 'What did hydroquinone ever do for us?'

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I think I'm gonna put that in my signature.

snusmumriken said:

'What did hydroquinone ever do for us?'

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Crawley ,BJP Dec 16 1960 p684 explained this.
"The presence of metol also assists discrimination in the highlights, which in some PQ developers are liable, the author finds, to 'run away'."
In other words, hydroquinone gives a more contrasty negative.

Alan Johnson said:

Crawley ,BJP Dec 16 1960 p684 explained this.
"The presence of metol also assists discrimination in the highlights, which in some PQ developers are liable, the author finds, to 'run away'."
In other words, hydroquinone gives a more contrasty negative.

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I don't have that paper available, but taking the quote at face value, isn't he comparing metol in MQ developers with phenidone in PQ developers?

Milpool said:

That's a big oversimplification. Superadditivity is not necessarily about contrast, although it is in some cases. It's about other aspects of sensitometry, image structure characteristics, capacity/stability etc.

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Yes, I accept that. So in those respects, what are we missing? I don't mean to sound challenging: this has been a puzzle to me for a long time, and nothing I've read has helped to resolve it.

snusmumriken said:

I don't have that paper available, but taking the quote at face value, isn't he comparing metol in MQ developers with phenidone in PQ developers?


Yes, I accept that. So in those respects, what are we missing? I don't mean to sound challenging: this has been a puzzle to me for a long time, and nothing I've read has helped to resolve it.

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Crawley is really not the best source on these things. One of the shortcomings of the Film Development Cookbook is an overemphasis on Crawley. Long outdated generalizations.

With respect to the other question, really you aren't missing very much. Relative to say D-23 or D-76, you can get a tiny overall (speed-grain-sharpness) advantage with XTOL, or small improvements in speed from some PQ general purpose developers (there are some exceptions). There really isn't much more to it.

At one time differences among developers could be somewhat more pronounced because the films were different. Emulsion technology is the gaping hole in discussions, debates and arguments about developers, and this is also a failing of much of the popular contemporary literature. Discussions about Rodinal, pyrogallol, solvent effects, edge effects, speed gains/losses etc. seem to largely ignore everything that has gone into emulsion engineering since the 1950s. Combine that with the strong tendency for us to see what we want to see in our negatives, and what you end up with are (at best) exaggerated claims.