Uneven development with Jobo. Help!!

[RPippin]

So I'm a bit baffled by this recent occurrence. Did a big shoot a couple of weekends ago, around 10 sheets of 8X10 and 20 sheets of 4X5. I started developing them in my usual manner with PMK Pyro in a Jobo. I have both drums, one for 5 sheets of 8X10 and the one for 10 sheets of 4X5. I've been getting pretty consistent results with them for the past couple of years, but this time, probably because of the importance of the project, most of them are crap. There is evidence of uneven development on some negatives, like no developer got the bottom of the tubes, streaks in some and a couple of 4X5's were blank. I know I could have a couple of things going on, definitely a Zebra in the works, but when I shot some 8X10's today and processed them with BTZS tubes, perfect! I have more 4X5's to develop and will use BTZS tubes for them to confirm my theory. So, how finicky really are these damn Jobo's? Should they be perfectly level? I use a drum roller, a bit worn out, and switch directions at even intervals. I use 500ml of chemistry, which should be more than enough. The only difference I can tell from last time is that I placed the roller on a different base in the sink. Should it have some grade to it? It appears that the chemicals don't get sloshed all the way in and out of the tubes. Nothing that drastic has changed in my method, or at least that's what I think. Thanks in advance for any advice I can get. If I can't resolve this, I'll go back to BTZS and you might find a couple of Jobo's on the For Sale list.

[Peter De Smidt]

The drum needs to be level. Perfectly level, no, but pretty level. For 8x10 film in an expert drum on with a CPP2, I always use 1 liter of developer.

[vinny]

Blank negs sounds like another issue no related to jobo drums.
I use 1L of PMK in expert drums split into two batches, 500ml for the first half of developement, 500ml for the second half because pmk is said exhaust when using rotary development. I get better results with this method.
No problems using a cpp2.
I presoak all films.
My machine is level.

[Vaughn]

The drum roller I use (Unicolor) was set up for alternating the direction of the drum -- but because the 3005 drum has a large diameter, there was barely a full turn (if that) before it reversed. So I disconnected it and flip the drum over about every 30 seconds or so. I also use about a liter of developer at a time in the 3005.

[vinny]

FYI, expert drums do NOT need to rotate in both directions to achieve proper development.

[koh303]

This sounds like insufficient liquid amount in the tank, or exhausted/contaminated developer.

[RPippin]

Thanks guys. Vinny, I use the split developer method as well, with the first 500ml for half the time and the second for the other half. My drum is fairly level. I usually sit the Unicolor on a tray turned upside down in my darkroom sink. It does rotate one direction and then reverse to the other direction, and I too have noticed the drum is to large to give a complete rotation so I switch over every two minutes of development time. The developer is fine, it worked beautifully on the four sheets of 8X10 I did in the BTZS tubes. The damn thing is just too finicky for my taste, so if I have to go back to the BTZS method for all but my 5X7 stuff I will, it's only 4 sheets of 4X5 shy and one sheet of 8X10. If I have to constantly watch the drum so that it tracks and doesn't come off the Unicolor, I don't know what the advantage of the Jobo is. Anymore thoughts? I might try disconnecting the direction thingy, Vaughn and see what happens. Thanks all.

[DannL]

I too "had" drums that were too large for the Unirollers. Having a spare uniroller, I opened the bottom and disabled the switch so it would no longer switch directions. I was able to use the 11x14 drums and even the Jobo drum for 20x24. After about 15 seconds in one direction I would lift the drum and swap it end for end. It worked very well. Try rolling the large drum back and forth on a counter top, table, or floor the next time you develop. Place a piece of tape on the drum as a visible reference point to insure you are rolling it a complete revolution or more. If all is well, I would suspect the Uniroller.

I would not exclude the design of the JOBO expert drum either. Using it with the Uniroller might be the overall problem.

[koh303]

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[RPippin]

Koh, got one of these too. Will try it out next time. And I'll disable the direction switch as well.