To Chemists: question about D-76 stock

Juan Valdenebro · Apr 16, 2021

Hello.
Please avoid talking about 1+1 or about replenishment: I know about them. And I like and use other developers, but this question is about D-76 stock only. Thank you.
I am enjoying using D-76 stock: I consider it the best developer for 35mm film when I don't want sharp grain but I need a slight push, say EI640-800... When I don't need that speed (tripod or wide aperture) I prefer Perceptol, at EI200. Those 2 f-stops of difference are key for handheld photography and stopping down with good speeds, in my case... I use D-76 stock for soft overcast light / ISO400 35mm film only. I have not tried it for medium format yet, because grain with 1+1 is not an issue in MF.
I'm using 360ml of D-76 stock for a 35mm roll, and then discard it. It's not too expensive, because some time ago I prefer to use at least 250ml per roll anyway... Here's the question:
I wonder why, chemically speaking, Kodak recommended in the past the use of 1 liter of stock D-76 to develop 4 rolls without increasing development time...
I understand the generous 250ml are not there for development only, but for controlling byproducts too... So, is it perhaps that the real amount of developing agents required is very small? If not, how could it be recommended to use several times the same liter that each time has a different composition after the development agents become less and less? Only if a really small amount of developing agents is enough for the task, I imagine...
I develop very few rolls of this type every month, so I don't want to replenish.
In case I decide to go from "360ml/roll and discard", to "4 rolls from a stock liter for reuse", economy would not change very much, although the bigger volume of the liter would allow me to "spend" only 250ml stock for 120 testing, instead of 600ml for discarding if I do MF...

Has someone used the 1 liter system for 4 rolls? Can it be true -chemically- film density doesn't change at all?
If the liter is always kept in an amber glass bottle filled to the brim, for how long should that stock solution work well?

Thanks.

MattKing · Apr 16, 2021

For context only - not as a "you should do this" post.
When you think about D-76, it is important to understand that it really wasn't designed for use in small tanks, for individual films.
It was designed to be used in large tanks, with large volumes of film and replenishment (in most cases).
A developer like that generally doesn't change a lot after a roll is developed in it - not like the developers that are designed to be used up one roll at a time.
It still can be used that way (in large tanks), but its most common use has evolved with the times.

Juan Valdenebro · Apr 16, 2021

And for decades it was recommended for stock use only, not diluted, I've read...
But even if replenishment is a good option for high volume and comercial use, that doesn't mean stock is inferior... Stock is the best option for the cases it's the best option: low volume, small format, high solvency...

Juan Valdenebro · Apr 16, 2021

MattKing said:
A developer like that generally doesn't change a lot after a roll is developed in it

Good to know that, thanks, Matt.

Juan Valdenebro · Apr 16, 2021

Then, maybe, without oxygen, the stock liter can work well for a few months...

Juan Valdenebro · Apr 17, 2021

by takilmaboxer, photrio, a few moths ago:
"The Kodak recommendation is 16 (sixteen) 35mm or 120 rolls per gallon without replenishment. That's 4 rolls per quart. My experience over the last 30 years is that this is a good recommendation.
Be careful with the Tmax films. D-76 activity gets higher with them over time resulting in denser highlights and loss of shadow detail."

Juan Valdenebro · Apr 17, 2021

I don't know if he meant the higher activity of D-76 is more visible on TMax films because they are more easily affected by changes than traditional grain films, or, byproducts from TMax films make the system less reliable...

MattKing · Apr 17, 2021

Old Gregg said:
@Juan Valdenebro yes, I have a Paterson tank which holds two MF reels. I can load four 120 rolls into those two reels, two on each. I use the same development time (and I get same results) for 4 rolls as if I had a single roll in my small tank. This is true for ID-11 (same ad D76) and Xtol.

That tank holds about a litre (~US quart). That is consistent with the manufacturer's capacity recommendation of 4 rolls per quart.
In addition, when you start out with a litre (or a quart) of fresh developer, there are no byproducts there to impede the initial development. If you had more than 4 rolls in the tank, then as the byproducts build up, the final bit of development might be partially restrained, but that wouldn't have the same effect as starting out with non-fresh, byproduct laden developer.

Juan Valdenebro · Apr 17, 2021

Old Gregg said:
TBH I am not sure what exactly is Juan asking... This is all quite straightforward.

Has someone used the 1 liter system for 4 rolls? Can it be true -chemically- film density doesn't change at all?
If the liter is always kept in an amber glass bottle filled to the brim, for how long should that stock solution work well?

I asked if the liter remains equally active (density on film) after one, two and three rolls, when days or weeks pass between those four development sessions. I prefer to develop films separately.

R.Gould · Apr 17, 2021

Juan Valdenebro said:
Has someone used the 1 liter system for 4 rolls? Can it be true -chemically- film density doesn't change at all?
If the liter is always kept in an amber glass bottle filled to the brim, for how long should that stock solution work well?

I asked if the liter remains equally active (density on film) after one, two and three rolls, when days or weeks pass between those four development sessions. I prefer to develop films separately.

Hi Juan, I have used D76, but as it is bacisily the same as ID11, which I use now, but I followed the Ilford method for ID11, and it works as well for D76 as for ID11, and gives you 10 films per litre, first film develop for correct, ( for my film, fomapan 400 8 minutes) then pour back into bottle of stock, then next film ad 10%, the add 20,30,40,50,60,70,80 an9 for the 10th film add 90%, then discard and start next litre, I have followed this method with both D76 and ID11, and the 10th film is as good as the the first film, important that, even if developing say 3 films developer be poured back into the bottle between films. and just to add that I have a i litre bottle that was mixed august last year,developed 5 films, and just tested it with the leader of a 35mm film as I have some films to develop today and it is working perfectly, so keeps at least 8 months
Richard

koraks · Apr 17, 2021

Juan Valdenebro said:
Has someone used the 1 liter system for 4 rolls? Can it be true -chemically- film density doesn't change at all?

Yes, it's perfectly plausible. As you hypothesized earlier, not a whole lot of developer is required to perform its function and the concentration in D76 is ample. Exhaustion is not an issue with 4 rolls/liter, provided the developer is stored properly in-between of consecutive sessions are undertaken.
The main concern is the buildup of development byproducts, particularly halides. However, their role is very limited with only 4 rolls per liter. Yes, there can be a theoretical/academic difference between rolls #1 and #4 if the rolls are developed in consecutive sessions. Perhaps it's even measurable. But the Kodak recommendation suggests it's not at all problematic.

Nicholas Lindan · Apr 17, 2021

If you go with the increasing development time approach that Ilford recommends for serial use of a liter of stock the 10%/20%/30% sequence may need to be adjusted for your film and developing technique. As mentioned, TMax films are much more sensitive to changes in development time. A 10% change in time with TMax will have the same effect as a 20% change with old-school Plus-X (I pulled the numbers out of my...).

My understanding of the Kodak 4 rolls/quart (liter, 1/100 cubic cubit ...) recommendation is either 8 oz/roll and discard or 4 rolls simultaneously and discard. I'm cheap so I use it 1:1 and discard. As they don't make Plus-X anymore, and my stock in the freezer is getting thin, I don't use much D-76 these days.

I would go with a version of the Ilford sequence. I don't know that I would go to the extreme of 9 rolls/qt - I can't see the characteristic curve holding constant with exhausted developer and a doubling of development time.

R.Gould · Apr 17, 2021

Nicholas Lindan said:
If you go with the increasing development time approach that Ilford recommends for serial use of a liter of stock the 10%/20%/30% sequence may need to be adjusted for your film and developing technique. As mentioned, TMax films are much more sensitive to changes in development time. A 10% change in time with TMax will have the same effect as a 20% change with old-school Plus-X (I pulled the numbers out of my...).

My understanding of the Kodak 4 rolls/quart (liter, 1/100 cubic cubit ...) recommendation is either 8 oz/roll and discard or 4 rolls simultaneously and discard. I'm cheap so I use it 1:1 and discard. As they don't make Plus-X anymore, and my stock in the freezer is getting thin, I don't use much D-76 these days.

I would go with a version of the Ilford sequence. I don't know that I would go to the extreme of 9 rolls/qt - I can't see the characteristic curve holding constant with exhausted developer and a doubling of development time.

It does with all Ilford film's, It does with Tmax, films, I have tried it with all Ilford films, and a friend has tried it with Tmax, and it most certainly does with Fomapan 200 and 400, the trick is to use only what you need per film, ( 300mm for each indivual 35mm film) and pour it back into the stock every time after developing, and it is 10 rolls per litre, 1 at normal time, then 10% ,20,30 40 50 60 70 80 and 90 for subsequent films 90% for the 10th film

Juan Valdenebro · Apr 17, 2021

Thank you all!
It's interesting... There are several options... I guess I'll do a few tests.
Maybe MF likes stock D-76 too.

Juan Valdenebro · Apr 17, 2021

R.Gould said:
Hi Juan, I have used D76, but as it is bacisily the same as ID11, which I use now, but I followed the Ilford method for ID11, and it works as well for D76 as for ID11, and gives you 10 films per litre, first film develop for correct, ( for my film, fomapan 400 8 minutes) then pour back into bottle of stock, then next film ad 10%, the add 20,30,40,50,60,70,80 an9 for the 10th film add 90%, then discard and start next litre, I have followed this method with both D76 and ID11, and the 10th film is as good as the the first film, important that, even if developing say 3 films developer be poured back into the bottle between films. and just to add that I have a i litre bottle that was mixed august last year,developed 5 films, and just tested it with the leader of a 35mm film as I have some films to develop today and it is working perfectly, so keeps at least 8 months
Richard

I don't know why I imagined long ago, that system (10%,20%...) might be risky and far from precise: a foolish thought no doubt... I should try that soon. Thank you, Richard.

R.Gould · Apr 17, 2021

I find it works very well indeed, I get 10 films per litre over a long period, as I said, the current litre was 1 of 5 that I has now had 7 films though mixed from a 5 litre packet I mixed last august, this litre has had 7 films though it, teo I developed today, with no loss of contrast or detail, just develop film, pour used developer back into bottle, it mixes with the stock ad ad the 5 and 6 % never had a problem yet, and it certainly keeps at least8 months

NB23 · Apr 17, 2021

So, if I develop 4 films at once in a 1L tank, I have to develop at T+30%, where films 2, 3 and 4 needing +10% each? This would be the logic.

And the next 4 films in a 1L tank would require to be developed T+70%?

And the last 2 films could be developed in a 500ML tank at T+90%?

The above is why I don’t use microphen, a developer I like. This method although economical for D76, and not so economical for microphen and perceptol, is not for me. Just better to develop 1:1 one shot. The film capacity will be similar to the +10% method.

lantau · Apr 17, 2021

I guess it is like the acceptable circle of confusion. Precisely speaking; dividing a litre of D76 into four 250mL portions and developing a roll of film in each will yield equal and perfect results.

Taking the whole litre and developing four rolls, one after each other should theoretically yield slightly thinner negatives each time. But Kodak will have tested and decided that the decrease in activity is small enough to ignore. Like the circle of confusion defining acceptable depth of field. For some the commonly used CoC will give fine results, for others it's not good enough.

I noticed on my 1938 Contax II that the depth of field scale seems much more generous than on modern cameras. Maybe you could even develop eight rolls of film in a litre of D76 back in 1938.

john_s · Apr 17, 2021

It all comes down to a trade-off. One person's adequate consistency might not satisfy another's. My take on this has been to make the investment to start mixing my own standard developers and use fresh each time. I would consider replenishment if I did more films.

NB23 · Apr 17, 2021

lantau said:
I guess it is like the acceptable circle of confusion. Precisely speaking; dividing a litre of D76 into four 250mL portions and developing a roll of film in each will yield equal and perfect results.

Taking the whole litre and developing four rolls, one after each other should theoretically yield slightly thinner negatives each time. But Kodak will have tested and decided that the decrease in activity is small enough to ignore. Like the circle of confusion defining acceptable depth of field. For some the commonly used CoC will give fine results, for others it's not good enough.

I noticed on my 1938 Contax II that the depth of field scale seems much more generous than on modern cameras. Maybe you could even develop eight rolls of film in a litre of D76 back in 1938.

In theory, 4 films developed in 1 liter would need 0% added time. But Ilford advises 30% increase, why I don’t know.

And then, the next 4 films in the same Liter of developer should need a global 10% increase if we go by the logic that the second film per 250ml of developer should be increased by 10%. But this logic, which is proper IMO, leads to a 40 rolls capacity per 1L of developer, not 10 rolls as described by Ilford.

The proper Ilford way is 10% per film, regardless of capacity per milliliter. I could be ok with that but I don’t accept that I should up the development by 30% if I develop 4 films at once in a 1 Liter tank with fresh developer because if one film takes 5 minutes to develop in 250ml, then 4 films should take 5 minutes to develop in 4 times the quantity of developer. There is no logical basis to add 30% development time. And thus, why should I up the next development of 4 simultanous films by 70%? Shouldn’t just 10% be enough?

This is why I’m not messing with Microphen, and that’s why I use my D76 stock, one-shot.

To me, the 10% method just doesn’t sit right. There are two logics working against each other and I just can’t wrap my head around each logic.

MattKing · Apr 17, 2021

Old Gregg said:
They don't. The data sheet says (quoting from memory) "if a series of films are developed in the same 1L, add 10% after each". When all four are developed at the same time, zero adjustment is required, as each roll gets 250ml of fresh developer.

And to emphasize the importance of fresh developer in that sentence, each roll starts out in fully active developer (not partially exhausted) that has no development byproducts in it.

NB23 · Apr 18, 2021

Old Gregg said:
They don't. The data sheet says (quoting from memory) "if a series of films are developed in the same 1L, add 10% after each". When all four are developed at the same time, zero adjustment is required, as each roll gets 250ml of fresh developer.

They say that 1L develops 10 Rolls max.

And they don’t say anything about “a series” nor anything about “the same time”. They just say that film 1= 0% adjustment.
Roll 2 = +10%
Roll 3 = +20%
Roll 10 = +90%
Roll 11 = not recomended.

Bill Burk · Apr 18, 2021

One day I was in a big rush to develop 24 sheets of TMY2 in D-76 1:1 and I did it in three runs for the same 13:30 time.
With a sensitometry strip in each run, I found that my contrast was diminished 15% each run.

My conclusion is that advice for minimum quantity of developer is intended to give amateurs consistent results for the same times. If you should extend the time but don’t, the consequence is reduced contrast.

I also concluded you can err 30% and still get good negatives, because all the negatives I got that day were just fine.

NB23 · Apr 18, 2021

Ok and what does it mean exactly? 1L develops 40 films developed in batches of 4? Or 10 total?

the microphen sheet doesn’t say anything about a “series”...

Old Gregg said:
Ok, I pulled it up. Copy-pasting from the ID-11 datasheet:

"If a series of individual films is being developed in a spiral tank using 1 litre of stock ID-11 or MICROPHEN or PERCEPTOL, compensate for the loss of developer activity after developing the first film by increasing the development time 10% for each successive film"

>>> Source <<<

Yep. Listen to Matt. He's never wrong.

MattKing · Apr 18, 2021

Old Gregg said:
Yep. Listen to Matt. He's never wrong.

I need to get you to speak to my wife.

To Chemists: question about D-76 stock

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