Divided developer pros and cons

[jbenedict]

Cool! I like the idea of letting my film imbibe. I rather like to imbibe myself... The kids had a hard time understanding how to make correct exposure. The use of the Divided D-23 caused many more of the pictures to come out usable.

[Jim Noel]

The effect happens by introducing the accelerator in the Part B. The film absorbs the amount of Part A it needs depending on density and, after it is drained of Part A, the Part B accelerates and causes the action. The areas which have absorbed less Part A are exhausted faster than the ones which absorbed more Part A. See the link I provided above for a full explanation.

I used the Divided D-23 formula with the metol and sulfate in Part A and borax in Part B. It did produce the compensating effect and worked well.

Sulfate or sulfite?

[Ed Bray]

Sulfate or sulfite?

or sulphate or sulphite even

[jbenedict]

Sulfate or sulfite?

sulfite

http://unblinkingeye.com/Articles/DD-23/dd-23.html

[Leigh]

With this method compensation takes place even with rotary development...
When the film is placed in Solution B the highlights develop first and then stop because the developer exhausts in this area...

Sandy,

Please realize that those two statements are diametrically opposed.

There is no way the developer can exhaust in areas of high density unless it exhausts in the entire developer volume, since rotation continuously replaces fluid contacting the film surface with fresh developer.

... a pre-soak does not fundamentally change the nature of development, though it will impact the speed of imbibition.

Given that a pre-soak fills all available space in the emulsion, where does developer part A go?

If you're relying on diffusion, that is a very slow process.

- Leigh

[richardman]

I have been using Sandy's divided Pyrocat for almost 3 years now, on 35mm, 6x7, to 4x5. I don't know how it works, but it works, especially with my scanning-post work flow. Not sure how they will work if I print optically but the negs look good in all types of conditions.

[sanking]

When the film is placed in Solution B, with a developer like Diafine or Pyrocat-HD where there is absolutely no image formation in Solution A, development is virtually instantaneous as it exhausts from the highlights to the shadows in about 1/10 of a second. Development is about 98% finished before the film even has time to make one rotation in a Jobo. If you have ever made a DOP pt/pd print development in two-bath solutions like Diafine and Pyrocat-HD is similar, i.e. the image just appears as if by magic as soon as the film comes in contact with the alkaline solution.

As for the pre-soak, I have tested it extensively with several two-bath developers and many films. The pre-soak changes the imbibition rate of Solution A, depending on the thickness of the gelatin emulsion and the temperature, but it does not do anything to harm the film or development. The factors that determine how much reducer can be absorbed in Solution A are 1) the pre-soak, 2) fillm type, 3) developer concentration 4) agitation, 5) pH, and probably several other unknown factors.

Two-bath D23 and D76 act a bit different than Diafine and Pyrocat-HD in that the sulfite adds enough pH to activate slightly metol. With Diafine and Pyrocat-HD the pH requirements of the primary reducers is very high so nothing takes place in terms of image formation until the film hits Solution B.


Sandy

[earlnash]

Everyone has parts of it right, but not all of it. The exposed portions of the negative do not absorb any more or less of the developer (reducing agent) than do the underexposed portions. The "compensation" occurs when the film leaves the developer. There is a fixed amount of it soaked into every portion of the film. Then, in the second solution, which is an alkali activator, the heavily exposed areas of the negative consume all the original reducing agent that is locally available, and then stop converting silver halide to silver metal. Meanwhile, the underexposed areas have a relative abundance of reducing agent (because there's been less activation of silver halide molecules), and develop further. The reactions go more or less to completion, which is why timing is not so crucial. Compensating, two bath developers work because there is limited substrate for the reaction. In contrast (heh!), regular one bath developers have a huge excess of substrate, so timing and temperature of the reaction is critical to limit the reaction. Agitation should not be a big factor for compensating developers, and more of a factor in single bath developers.

[Leigh]

The "compensation" occurs when the film leaves the developer. There is a fixed amount of it soaked into every portion of the film. Then, in the second solution, which is an alkali activator, the heavily exposed areas of the negative consume all the original reducing agent that is locally available...

This is precisely my point.

How do you define "locally available" in a rotary processor that's constantly refreshing the liquid in contact with the film?

In a rotary processor, the term "original" (as above) is meaningful only when it refers to the entire volume of developer, not to a portion thereof.

- Leigh

[Cor]

As I understand it:

First the film is put in the Jobo for rotary processing and filled with reducer for a certain amount of time, temperature, rotation speed.

Then the tank is completely drained, leaving only the wet, soaked with reducer, film behind (finite amount of reducer) . Obviously no water wash in between.

Last the alkali (B) is added to the tank and rotated, and development takes place almost instantly as I understand from Sandy.

If I did not understood it correctly, I am sure more experienced practitioners will chime in.

Best,

Cor

This is precisely my point.

How do you define "locally available" in a rotary processor that's constantly refreshing the liquid in contact with the film?

In a rotary processor, the term "original" (as above) is meaningful only when it refers to the entire volume of developer, not to a portion thereof.

- Leigh