A question for Chemists... Not a simple one... Setting a two-shot system for D-76.

Juan Valdenebro · May 3, 2021

Another interesting fact -and something I've read about a few times in the past- is stock D-76 gets more out of the shadows than D-76 1+1.
That's why above box speed (as is my case with EI640) or for pushing 1-2 stops, it's D-76 stock what's recommended, and not 1+1.
With stock, films have richer shadow detail when slightly uprated.
Materials are out there for anyone to check this.

Juan Valdenebro · May 3, 2021

Again, Chemists may know:
In the official 1 litre for stock reuse system, adding 10 percent of development time per roll, is it possible that byproducts are as well controlled as to produce 38 identical rolls (grain and tonality) from a gallon of D-76? It seems (to me) an amazing amount of rolls... And an amazing level of chemical control !
If that's true, it would be the best way to use D-76... Why isn't it the most common use of D-76?

Juan Valdenebro · May 3, 2021

michael_r said:
Re-use and replenishment are both compromises for economy.

Hi Michael,
It seems you're implying official reuse doesn't produce stable grain/tone negatives...

Juan Valdenebro · May 3, 2021

michael_r said:
If you follow the manufacturers’ directions for re-use, results will likely be stable enough unless you are attempting to maintain precise process control, using a microdensitometer etc.

That's great... Maybe I should try a litre of stock adding 10 percent time... Perhaps that would be a great way to use stock for MF.

Bill Burk · May 3, 2021

Juan Valdenebro said:
Hi Bill,
Yes: I consider it's possible to use 1+1 even for soft light... Indeed, I wrote (here) I do that for MF... It's small format ISO400 what I prefer with stock.
I guess I'll end up using 360ml of stock for the small rolls, one shot and discard, instead of 250ml for 1+1: no big deal in the end, and a very small price for comfort and image quality.
That's easier, faster, and more relaxing than using stock twice.

I missed where you said why you use more than needed to cover the film? Why not use 250 ml stock in a steel tank for a roll of 35mm film?

Juan Valdenebro · May 3, 2021

Bill Burk said:
I missed where you said why you use more than needed to cover the film? Why not use 250 ml stock in a steel tank for a roll of 35mm film?

I have not said that, Bill...
I'm OK with my tank and with 360ml for a small roll... That I said...
Another thing I said is 600ml for a single MF roll was what made me think of a different way to use stock, and that's why I asked about smaller/thinner tanks for MF...
But it seems adding time can keep the results I love from fresh stock...
I don't know if I will try as much as 10 rolls from one litre, though.

Juan Valdenebro · May 3, 2021

michael_r said:
Disclaimer - I’m not a chemist.

Don't worry, Michael, thank you.
It must work at least more or less, and at least for the first four rolls...

MattKing · May 3, 2021

Here is my suggestion:
Use the 10% increase method to develop ten rolls of film that are exposed normally - different subjects, varying light, etc. The order of development should be randomized - don't develop them in the order they were shot.
Make a point of not looking at the negatives until all ten rolls are developed.
Have someone else label the rolls in some sort of code that indicates what order they were developed in, so that until the code is revealed to you, you won't be able to tell which roll was developed at what point in the ten roll sequence.
Try to guess the order of development.
Then compare your guess with the code, to see how you did with your guesses.
I would be willing to bet that you won't be able to guess at the order of development.

Donald Qualls · May 3, 2021

Juan Valdenebro said:
is it possible that byproducts are as well controlled as to produce 38 identical rolls (grain and tonality)

Thirty-eight rolls!?

I'd be surprised if you had anything on the film by the last roll, processing 38 rolls in a single liter of stock solution -- and you'd be up to 37.4 times (1.138) your original development time to try to get there. You ought to manage 38 rolls in a gallon (which is 3.8 liters) -- that would only be ten rolls per liter, and Kodak rates the extended time method as good for up to 15 rolls in a liter. BUT!! You'd want to divide up the gallon into quarts, else 10% would be too much compensation (10% for each four rolls would be close to the mark if you're using a one gallon batch of stock solution).

Bill Burk · May 4, 2021

237 ml per sheet of 8x10 is the recommended stock. That should give 16 sheets 8x10, 16 rolls of 35mm or 8 rolls of 120 per gallon of stock, right?

I regularly violate the minimum recommended stock per square unit of film.

I most commonly use a steel tank that holds a quart of liquid.

It holds 2 reels of 120, or 4 reels of 35mm

I mix my D-76 in quart bottles. When I develop film, I use half the bottle as I mix up the 1:1.

So for a gallon of stock, I get 32 rolls of 35mm film, or 16 rolls 120.

In trays I put 16 ounces of liquid and process 7 sheets of 4x5 film. (One Grafmatic and a sheet of sensitometry).

So effectively when I do 4x5 I work at a rate of 112 sheets of 4x5 per gallon.

16 sheets 8x10 -> 28 sheets
64 sheets 4x5 -> 112 sheets
16 rolls of 35mm -> 32 rolls
8 rolls of 120 -> 16 rolls

So my developing times may not compare to what people who respect the minimum stock solutions get. But they are consistent.

Rudeofus · May 4, 2021

Juan Valdenebro said:
Hi Michael,
It seems you're implying official reuse doesn't produce stable grain/tone negatives...

That developer most definitely be a different animal after some rolls. Various halides will build up, some of the Hydroquinone and the Sulfite will react to HQMS. These changes are the reason, why Kodak recommends +10% dev time per roll. pH will change in some random way. This is, why @michael_r wrote "unless you are attempting to maintain precise process control".

To make a long story short: if you can reliably detect a difference between D-76 stock and D-76 1+1, then you will also see a difference between D-766 fresh stock and D-76 stock after roll #3.

Lachlan Young · May 4, 2021

Rudeofus said:
That developer most definitely be a different animal after some rolls. Various halides will build up, some of the Hydroquinone and the Sulfite will react to HQMS. These changes are the reason, why Kodak recommends +10% dev time per roll. pH will change in some random way. This is, why @michael_r wrote "unless you are attempting to maintain precise process control".

To make a long story short: if you can reliably detect a difference between D-76 stock and D-76 1+1, then you will also see a difference between D-766 fresh stock and D-76 stock after roll #3.

I know this is risking a trip down the rabbit hole of reformulating a D-76-alike, but I note that Foma's Retro Special developer claims that for up to 0.8m2 of films processed in it (about 15 rolls 135/120/ 8x10 sheets or so?) it needs no processing time alterations. It's pretty highly active compared to D-76 however - from some recollection, I have a vague suspicion that it uses fairly serious buffering (carbonate based?) and quite a lot more M & Q than D-76, though at roughly similar ratios as in D-76 - so it isn't simply something like DK-60a or DK-50.

A question for Chemists... Not a simple one... Setting a two-shot system for D-76.

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