Photo Engineer
Subscriber
Seeing posts on APUG regarding divided developers for B&W and even for color, I feel moved to make one very important point for you who favor this method.
A divided developer works by imbibing, or soaking up, part A and then carrying it over into part B where development takes place. It relies on imbibing the right amount of developer, and then it relies on exhausing it either by use or diffusion in the two step operation.
Now, here are the problems.
Divided developers are dependant on swell and thickness of the film. If either or both of these vary, then the results will vary regardless of the ability of the film emulsion itself to respond.
If a manufacturer makes a film "X" and then improves its sharpness by coating less gelatin, then the emulsion is thinner and swells less. Regardless of the fact that may be the same emulsion, it will respond to a regular developer as desired, but will respond to a divided developer in a different, and less effective manner.
If a manufacturer were to change from formaldehyde hardening to glutaraldehyde hardening, the coating would be as hard, but would swell slightly more in the latter case, giving more reactivity to a divided developer, but the normal reactivity to a normal developer.
Therefore, you should very carefully examine each film for your divided developer before going ahead with a given project, or you may not get what you expect. Coating formulas change all the time.
If Kodak or Ilford were to change the speed of the coating machine, for example, they would re-formulate the film to give identical results in a given developer. They cannot test all possible developers, so they have a standard release test. If the film works, it is sold, but this change, whatever it was, would impact more heavily on the divided developer.
I suspect that is why modern films seem to work less well in divided developers. Among other things, they are much harder than older films by virtue of using a different hardener than the old formalin hardener. They are thinner, because t-grains are only 'two dimensional' rather than 3 dimensional 'rocks' or klunkers as we called them. Therefore, less gelatin has to be coated. The 3 D grains would stick up out of the gelatin if there was not enough gelatin to cover them. (that is a simplistic picture but you get the idea).
PE
A divided developer works by imbibing, or soaking up, part A and then carrying it over into part B where development takes place. It relies on imbibing the right amount of developer, and then it relies on exhausing it either by use or diffusion in the two step operation.
Now, here are the problems.
Divided developers are dependant on swell and thickness of the film. If either or both of these vary, then the results will vary regardless of the ability of the film emulsion itself to respond.
If a manufacturer makes a film "X" and then improves its sharpness by coating less gelatin, then the emulsion is thinner and swells less. Regardless of the fact that may be the same emulsion, it will respond to a regular developer as desired, but will respond to a divided developer in a different, and less effective manner.
If a manufacturer were to change from formaldehyde hardening to glutaraldehyde hardening, the coating would be as hard, but would swell slightly more in the latter case, giving more reactivity to a divided developer, but the normal reactivity to a normal developer.
Therefore, you should very carefully examine each film for your divided developer before going ahead with a given project, or you may not get what you expect. Coating formulas change all the time.
If Kodak or Ilford were to change the speed of the coating machine, for example, they would re-formulate the film to give identical results in a given developer. They cannot test all possible developers, so they have a standard release test. If the film works, it is sold, but this change, whatever it was, would impact more heavily on the divided developer.
I suspect that is why modern films seem to work less well in divided developers. Among other things, they are much harder than older films by virtue of using a different hardener than the old formalin hardener. They are thinner, because t-grains are only 'two dimensional' rather than 3 dimensional 'rocks' or klunkers as we called them. Therefore, less gelatin has to be coated. The 3 D grains would stick up out of the gelatin if there was not enough gelatin to cover them. (that is a simplistic picture but you get the idea).
PE