Rodinal temperature and agitation

[alan_rockwood]

I have read that I should avoid using Rodinal for high temperature processing

(greater than 68F) or with constant agitation (e.g rotary tube.) What are the

bad effects of each individually and in combination?

 

Related to this, I have also read that Rodinal is less sensitive than most

developers with respect to processing times as a function of temperature, and

one book I have checked out of the library even gives a quantitative comparison

between different developer components. This almost seems to contradict the

advice to avoid Rodinal at high temperatures. Could someone comment on this as well?

 

Thanks.

 

Alan

[chris_waller]

Alan,

 

As a Rodinal user of some twenty-odd years I have always used it at 20 C except on odd occasions during very hot summers when I've worked up to 23 degrees C. I certainly observed no ill effects and Agfa quote times for temperatures up to 24 C. In times past temperatures above 24 C were not advised due to the softness of emulsions and the likely damage. However, chemically, Rodinal should be perfectly stable well above 24 C and, as you have read, is very linear against temperature. I reduce times by 10 percent per degree C above 20 C and increase by 10 percent per degree C below 20 C. Some developing agents drop rapidly in activity below a certain temperature- hydroquinone becomes very inactive below 16 C.

 

As for agitation, Rodinal is an acutance developer and relies on edge-effect for its sharpness. It has been argued that excessive agitation can reduce the sharpness due to a reduction in the edge-effect (also known as the adjacency effect). In my own case I agitate by inverting the tank once every 30 seconds.

[rustys pics]

I've used Rodinal at 75 degrees F. or 24 C. with no ill effects. Just have to reduce time as

noted by the previous post. I don't know about rotary processors though. In my opinion they

over agitiate and blow highlights. Never liked them, too big and messy for black and white

film.

[dakotah_jackson]

Rodinal, especially with the additions of Sodium Ascorbate works well for rotary processing. Nice and clean negatives with the sharpness Rodinal is famous for.

[profhlynnjones]

I've tested it from 65F to 75F with no discernable difference except that in lower dilutions the developing times could be too short.

 

Lynn