Uneven development in a unidrum?

[Nitish Kanabar]

I used a unidrum print processor on a uniroller base to process 4 sheets (4 x 5 inches) of FP4+ in 8oz of undiluted D76 at 68 degrees for 7 minutes. All 4 sheets came out with uneven development about 0.25 inches from the short edges. The uneven development shows up as a streak running roughly parallel to the short edges - with a slightly higher density in these areas. Originally I thought that the developer touched the film edges during pouring, but that would cause only one edge of the film to be overdeveloped, not both. Another thought was that the chemistry was splashing around the flanges that hold the edges and thus over-agitating those parts of the film - but again others would have seen this too - and I know that many on this forum successfully use the unidrum & uniroller on a regular basis.

What am I doing incorrectly here?

Thank you in advance for your suggestions.

--NK

[Robert Ley]

When I used the unidrum to process 4x5 film I used atleast 12oz of chemistry. If you don't use enough chemistry you will get uneven development on the ends of the film.

[Philippe Gauthier]

I never use more than 125 ml (less than 5 oz) of chemistry in my 10 inches Unicolor drums and my negatives are always beautiful using HC-110. I never pre-wet film.

The only thing I can think of is that perhaps the sheets move and overlap during processing?

[dee seegers]

I use 300ml of D-76 1:1. No problem. I use the auto-reversing base.

dee

[Jerry Thirsty]

I saw this when I first began. I was rolling it by hand on a Jobo roller base. I think it was insufficient agitation, because rolling it more vigorously got rid of the problem. But if you are using a motor base I would think it should be fast enough.

[Dave Schneider]

What is holding the film in place in your drum? Are you using a print drum with the big ribs? I tried all sorts of modifications to drums and never found a good solution. Any ridge or clip to hold the film in place would cause a little bit of turbulence or prevent even developer flow. The result was the same, uneven development. I found the best results with larger liquid volume and slower rotation. Still, I was never satisfied with the results.

[Nitish Kanabar]

The films are separated by tiny rubber stoppers to prevent them from overlapping. They're held to the drum by the ridges - and it is along those edges that the uneven development is seen. I am using the unicolor print drum on a self-reversing roller - reversing direction after completing 1 complete rotation of the drum. I did not see any means to control the speed of rotation.

Basically my setup is identical to the one described by GreyWolf here http://www.largeformatphotography.info/unicolor/.

I'll experiment with different chemistry volumes to see which works best.

thank you all,

--NK

[Dave Schneider]

NK, I went so far as to use a clear acrylic end cap on my drums for testing. I watched the turbulence created at the retaining ridges at various rotation speeds and with various liquid levels. Once I did that it was clear to me I would never be satisfied with the drums. I tried Cibachrome drums which are completely smooth inside and made various shapes and sizes of ridges, clips, etc to hold the film. I was never satisfied. I ended up making rubes from 1.5 inch ABS pipe to hold a single sheet. This has provided much better results than I ever achieved with the drum. Your results may be different, I know some people swear by them.