D76 x:1

I have a 2+ litre Jobo tank, made for 2 reels holding 12 4x5 sheets. I use it to develop 6 120 rolls on a Uniroller. I like to develop in D76 1:1. 6 rolls require 1400ml of full-strength developer, leaving about 500ml of added water to keep the film covered through the full circle. So my mix is more like 3:1.

Do I:
1) Use the regular time from the data sheet for 1:1 because it is the same amount of developer as in 1:1, or
2) Some sort of time adjustment because it more concentrated?.

Have you considered using D-76 1:1 and just being short of the recommended stock solution per roll?

Bill, I have done the 1:2 solution with the 10% added time as mentioned in the data sheet and it seemed to work alright. So yes, I could try that. However, my basement is 63F/17C, off the Ilford adjustment chart and in the Kodak "not recommended" territory. I did tmax 400 on Monday at around 15-17 minutes. I'm loading up HP5 right now.

You probably are better off with the higher concentration of stock because it will help you keep the time reasonable at the cooler temperature. 15-17 minutes sounds right for TMY-2

If mixing 1:1, and your stock solution is 63F, add an equal amount of water at 73F to get a final solution at 68F.

gary in nj said:

If mixing 1:1, and your stock solution is 63F, add an equal amount of water at 73F to get a final solution at 68F.

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Good idea.

pbromaghin said:

I have a 2+ litre Jobo tank, made for 2 reels holding 12 4x5 sheets. I use it to develop 6 120 rolls on a Uniroller. I like to develop in D76 1:1. 6 rolls require 1400ml of full-strength developer, leaving about 500ml of added water to keep the film covered through the full circle.

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2 litres of developer for 6 rolls of 120 in a Jobo tank rotation development? Are you sure?
12 4x5 sheets in one tank sounds like a 2563 tank (Multitank 6) which is capable of holding 6 120 films - and that requires min. 850 ml of liquid for rotation development.
Kodak data sheet states a required amount of 16 ounces per 2 films 1+1 diluton, so your calculation of about 1400ml for 6 films is correct. But why do you want to fill it up to 2 litres?

RauschenOderKorn said:

2 litres of developer for 6 rolls of 120 in a Jobo tank rotation development? Are you sure?
12 4x5 sheets in one tank sounds like a 2563 tank (Multitank 6) which is capable of holding 6 120 films - and that requires min. 850 ml of liquid for rotation development.
Kodak data sheet states a required amount of 16 ounces per 2 films 1+1 diluton, so your calculation of about 1400ml for 6 films is correct. But why do you want to fill it up to 2 litres?

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2563? Thank you, I've never found any identifying marking beyond "Jobo".

The most basic answer to why, is because I'm working backward from 1:1, which would be 2800ml. My main concern is the difference in concentration at 2000 vs 2800 - do I need to adjust time because the concentration is closer to working solution, or keep the same time because it is the same volume of working solution?

The tank will take 2100ml to fill when standing on end. I am double-stacking 120 film on 3 reels. There is a couple-centimeter space between the edge of the reels and the tank wall, so 2 litres pretty much assures all film is always covered in liquid while turning. 1400 ml would still fill it above 1/2, so all film would dip down into the developer - but how evenly and would I still use the 1:1 time?

Here's what I think will happen:

The more concentrated the developer, the faster it will act. So you will need to pick a time between 1:1 and stock. But you said it's cold there... so I was thinking the real time might be same as 1:1 at 68-degrees F (once you factor the temperature)...

Less than the recommended amount of developer per square unit of film surface area, the more development by-products will affect the rate of development... leading to less predictable development times. This might be a laboratory-condition difference when you are developing one-shot. I think the recommended amount of developer per unit area is more important when you are developing several rolls in a stock tank. Then after you have done that many rolls, you replace the developer to keep the next roll from having wildly different time due to development by-products. I once ran three batches of 6 or 7 4x5 sheets in 16 ounces of D-76 1:1 and I learned first-hand what they mean when they suggest 15% additional time if you go beyond the recommended capacity. (My first run was fine, but the second run could have used 15% more time... and my third run could have used another 15% more time).

So I would do 1:1 and only use the "right" amount to fill the Jobo tank to the most appropriate liquid level, then I'd add 15% to the 1:1 time to adjust for the fact that I was using less than the recommended amount of developer per square unit area. (Actually I'd be doing sensitometric exposures and densitometer readings and graph the results to come up with film characteristic and time-contrast curves... but I expect the story would be the same).

pbromaghin said:

Thank you, I've never found any identifying marking beyond "Jobo".

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I have one of these tanks myself, no sticker, just a Jobo imprint. I guess they were sold like this after Jobo went Chapter 11 some years ago.
You should try to find out which tank you really have by comparing with pictures from the internet. You can then find a photo of the sticker, which states the appropriate amount of liquid required.

pbromaghin said:

The most basic answer to why, is because I'm working backward from 1:1, which would be 2800ml. My main concern is the difference in concentration at 2000 vs 2800 - do I need to adjust time because the concentration is closer to working solution, or keep the same time because it is the same volume of working solution?

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I am confused. I´d mix a batch of undiluted developer, which will have sufficient keeping properties to be stored a while. Take 700ml and add 700ml of water, and that´s it. Right amount of developer at the right dilution. And the rest of the undiluted developer can be stored.

Have you ever considered getting yourself a Jobo processor? The CPE's aren't that expensive second hand, will allow you to use rotary development and more importantly in your case: temp adjustment in your basement, so you can develop at 20 C.

Then: if i am not mistaken: one 120 roll or one 135 roll or 4 sheets of 4x5 require 100ml of stock solution of D76. So when developing 6 rolls of 120 film, that would be 1200 ml fluid for 1:1. When doing 12 sheets of 4x5 you could suffice with 600 ml fluid. Why are you using such large amounds of fluids for rotary processing? It doesn't matter if you use 1200 ml of 2.5 l of working solution as long as the minimum amount of stock is used.

RauschenOderKorn and Huub,

I found the tank capacity by filling it up with water and dumping it into a graduated cylinder. According to the D76 instructions 700ml of developer concentrate is only good for 3 rolls of 120 film. I am doing 6 and so I need about 1425ml of full strength developer.

Yes, I have considered getting a Jobo, but am getting along well with a Uniroller (and Phototherm circulating bath for C-41). Controlling chemical temperature would require also controlling rinse water temperature, but with buckets for water supply and waste, that would be very inconvenient. Working at room temperature means all liquids are the same.

pbromaghin said:

I am doing 6 and so I need about 1425ml of full strength developer.

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I was referring to the following line from the Kodak Data D76 sheet:

"To extend the useful capacity of Developer D-76 diluted 1:1—when processing two 36-exposure rolls in a 16-ounce tank—increase the recommended time by about 10 percent."

So 1,4 litres 1:1 will be sufficient developing 6 rolls with a small adjustment in the development time.

Ah, got you. I have done this in the past and it seemed to work fine.

Bill Burk said:

You probably are better off with the higher concentration of stock because it will help you keep the time reasonable at the cooler temperature. 15-17 minutes sounds right for TMY-2

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+1