View Full Version : How often should rotary agitation reverse?

16-Jun-2016, 15:29
I'm bodging together a rotary agitation setup for processing 4x5 and 120 film. I've got a Jobo tank and a Color by Beseler roller base. Given the diameter of the Jobo tank, the Beseler roller base reverses direction every 1 and 1/8th revolution. So at least it's making a bit more than a full revolution before reversing. This seems a bit fast to me (compared to experience a decade ago with an actual Jobo processor). Will this work or does the tank really need to run in one direction for longer than that?

16-Jun-2016, 15:43
The Beselers rotation is just right. No worries.

David Karp
16-Jun-2016, 16:54
Mine does not make even a full revolution with my Jobo drums. I used to let it go in one direction and just lift the drum and turn it around periodically. I read some posts on the forum that said there was no need to reverse the drum so I tested that and found it to be true. I just let it rotate in the same direction. I don't think that would be true with the Beseler drum.

16-Jun-2016, 17:07
[... please see David's post ...] I don't think that would be true with the Beseler drum.


Kevin J. Kolosky
16-Jun-2016, 17:28
I have often wondered whether a windshield wiper assembly would work in some fashion with its back and forth action.

David Karp
16-Jun-2016, 17:41

My understanding was that the shape of the tubes in the Jobo drums caused the chemicals to have a random and uneven flow, even when the drum rotates in only one direction. The Beseler drum that I owned had straight walls, so reversing direction would be necessary to disrupt the flow of the chemicals while rotating.

Victor Loverro
16-Jun-2016, 19:15
I have used the Beseler but am now using a Unicolor which turns in one direction only. I reverse the drum about every two minutes. I use it for 4x5, 5x7 and 8x10 Jobo drums. I once let the drum turn in one direction only for the entire processing time and could see no difference between negatives processed by reversing the drum. No uneven development or streaking. Densities as expected. I use Pyrocat HD developer.