Jobo Processing

[Richard White]

Response to Bob Carnie

With regard to processing 4 x 5 shhet film in a Jobo. I am not using distilled water. I use rain water. This was not an issue before. It's confusing. I also use the black inserts. Have hand processed film in the Jobo tank and no problems. It is obviously the movement of the drum.

The added density is along the long side of the film which would be in the direction of the water flow. The middle and inside films seem not to be affected. Obvious solution don't load film on the outside or hand process, but....

Anyway I will keep at it. If you or anyone can offer any other hopeful solution then I would be grateful. I didn't tell you that I live in Australia. This in itself could be the cause.

Cheers from Down Under, Richard

[bob carnie]

Hi Richard

Try the distilled water, just for peace of mind, I do believe it could be laminar flow problems, distilled water allows the chemicals to flow onto the film easier.
Manual agitation is definately an answer as you can disrupt the flow pattern.
good luck

[Kirk Keyes]

Bob - could you explain by what mechanism distilled water allows chemicals to flow onto the film better than non-distilled water?

[bob carnie]

Kirk
My understanding is that the minerals in regualar water cause a friction that does not allow the chemicals to flow freely over the film, as it rotates, wheras distilled water is free of minerals and allows the developer to move faster over the film.
I have found this to be critical in the first few rotations of film development. We have tried both over the years and distilled water has always been cleaner.

[paulr]

The important thing about distilled water is that we know what's in it: water.
Tap water, rain water, well water, bottled water, etc., can have all kinds of things in them. Just a few of the variables are pH, mineral content, chlorine content, fluoride content.

As an example of the consequences, effective washing times vary enormously from one tap water source to another; researchers have their theories but no one really knows why.

The idea of minerals in the water causing friction sounds a bit contrived--i'm more likely to believe it has to do with surface tension-- but then again, I don't know, and I'll bet no one's spent the research money to find out.

We're in the world of empirical knowledge with this stuff. The best we can do is try something, systematically if we have the patience, and then share it with friends, so they don't have to waste a day of their lives too!

[paulr]

oh, another thing ... have you talked to the tech guys at Jobo? it's been a while, but they were always incredibly helpful, and they really knew what they were talking about.

and a few things that have helped me get even negs with a jobo drum:
-an alkaline presoak. just a bit of sodium metaborate in the presoak water, and presoak for at least a couple of minutes.
-make sure the machine reverses before flow patterns get a chance to develop (i think the jobo guys recommend reversing every five seconds)
-consider your developer. developers that encourage edge effects (from bromide sensitivity) also tend pose evenness challenges.

[Nick_3536]

The minute you add anything to the distilled water it's not just water anymore. Add developer. Breath on it. whatever. It changes. Put me in the confused camp on distilled water.

[bob carnie]

Hi Paulr
I have never considerd a alkaline presoak, I will try it this week.
I use a ALT2300 and I am not sure I can program the rotations to every five seconds. it is interesting though you mentioned this as I do believe this is the problem Richard is having . We let the machine rotate once then we manually take off the drum and and give a complete inversion as if working with stainless steel tanks. We then put the drum back on machine, rotate again , then take off again complete inversion, we do this three times in the first 45 seconds of development. This method completely eliminated a problem we were having with 120 film in the jobo.

Regarding distilled water vs regular tap water (not softened) I suggest a simple test.
(to keep it ok for the large format people use a 6x9 back on your large camera)

Expose two 120rolls of trix @ISo200 , identical NUETRAL background
Develop on a rotary processor, using Hutchings PMK formula, two different runs (normal)
first film use tap water
second film use distilled water
Lay the two films on a light table and you will find a minus density lines on both sides of the film running approx 1mm into the image area in the direction of the rotation of the Jobo. It will be present on the film that was run in tap water, the film ran in distilled will not have the minus density lines.
I have tried this many times to verify this problem.... ( It may be the ph of the water in Toronto, but I know this problem exists)

Richard elimatate these two problem areas and I believe you will be closer to correcting the lines you described

[Steve Feldman]

Hi ya'll. (I'm not from the South - just like sayin' that).

I've been processing B & W in L.A. for the past 20 years. 35mm, 120/220, & 4x5 films in a Unicolor Drum. Always with tap water (OK for film/paper processing - don't drink the stuff). I used to get processing streaks, pin holes and air bells. My cure? One drop of Photo Flo in the pre-soak AND in the developer. I'm sure that this breaks the suface tension and stops streaking. It just makes the liquids, well, er, ah, . . . . . flow.

Works for me.

Your mileage may vary.

[Nick_3536]

Toronto water is full of calcium carbonate with a pH of about 7.5. I still don't understand. Once you've added all the stuff in the developer is the mineral level in the water really that important?