AGITATION MADE EASY AND PREDICTIBLE

I get that turbulence is necessary for mixing exhausted and non exhausted developer inside the tank, so slow constant rotation, without rotation inversion, is not good.

Rotation inversion should create a swirl that shakes chemicals inside the tanks, just like a washing machine shakes the laundry, which I think my Jobo does (at 80 rpm and a rotation inversion every 3 seconds or so).

It is also possible that the German magazine made the tests with a full tank. When using horizontal rotation one normally uses "half" volume of chemicals and that allows the chemicals to swirl inside the tank at every rotation. If the tank is full, rotation inversion would not swirl chemicals that much.

The same can apply to rotating the axe of a Paterson tank while keeping it vertical. If the tank is full (as it must be in that case) the rotation of the reel can be not sufficient to mix the chemicals inside the tank and the film might remain in contact with already exhausted developer.

Theres a reason why the Jobo processors change direction during rotation. Rotating alone is no guarantee for even development. Rotation starts a flow in the developer itself causing different flow rates on different film areas which in turn (depending on developer) changes development rate locally.

"If the tank is full, rotation inversion would not swirl chemicals that much".

Such was Diapositivo's response which makes as much sense as I am able to make. Merely 'twirling' the tank IN the solution will not agitate as effectively as 'REMOVING' the film (as the 'water wheel approach' I recommend) with the tank HALF EMPTY SO THAT THE FILM WILL COME OUT OF THE SOLUTION AND THEN IMMEDIATELY GO BACK INTO IT. The few drops of leakage does not matter. Put the tank, horizontally, in a water bath and THROUGHOUT the development cycle keep rotating the tank. PERFECT NEGS EVERY TIME!!! Why does there always have to be someone advocating a VIOLENT BANGING OF THE TANK TO DISLODGE AIR BUBBLES IN THE 'PROFESSIONAL' LITERATURE? Just try to imagine yourself as the film: wouldn't continuous in and out of the developer make you the most likely to get developed. When film is CONSTANTLY IN THE SOLUTION THE SOLUTION'S WAVES ARE NOT AS EFFECTIVE AND THOROUGH. (Hope this clarifies.) - David Lyga

David,

Your method is surely workable but, it is not a silver bullet. It still requires a learning curve because the agitation speed and if used, direction changes, must be mastered and these do affect development.

Measurment is the only reason any film should ever miss out on being fully covered and measurement is a skill that has to be mastered regardless of method. Under filling the tank in your method still results in some film missing out just as it does in any other method.

Your thought on temperature float causing better development and the waves in the tank seem to be just plain conjecture and bad science on your part.

Banging/tapping the tank doesn't need to be violent but it is an important (and dare i say well proven) part of agitate and wait methods.

I'm not dis'n rotation, it has it's place, heck I even use it for all my C-41 work in my JoBo.

That said for B&W I actually prefer stainless reels & tanks and standard Ilford agitation. Simple, easy, and, after the rookie mistakes are behind us, perfectly reliable.

And for goodness sake stop yelling (easy on the caps). The world will not end if we don't convert.

So what happens if you reach the end of your tabletop? Or do you roll your tank on the street?



Sorry, I just had to make a childish joke.

Very good point here, as the road ruts can close a film line,,, I know.

this is why we recommend and do, inversion and rotary.

piu58 said:

If you roll the tank instead of inverting it you get acummulation of bromide rich developer in the inner part of the roll, This leads to lesser development there. I recommend continuous inverting. Please keep in mind that you have to shorten the development times in comparision to 30 second iversions.

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There will always be attempts at re-inventing the wheel.

Once again, an insightful tidbit by Prof. Lynn Jones, a veteran "Brookie". I have used the "Boris Dobro" method for years, and NEVER had any issues. Other methods work as well, but I always know what I am going to get when I follow these rules:

"It is very important, however, the published inversion and rotation systems are horrible, just barely better than than no agitation at all, but not much better.

Regarding the plastic tanks with the "spinner" type agitation, this actually works! For the first 15 seconds, spin two to the right and two to the left repeadedly. After than, for each cycle, 2 to the right and 2 to the left and leave it alone 'til the next cycle. If you fog film to a density 1.00, this will give you 1.00 +/- .04 to .05, (1/6th to 1/7th f stop) that is quite good relative to the information given to us by Kodak back some years which says that +/- .20 is an acceptable range (total of 1 1/3 stops), I don't think so.

A good rotary drum with continuous reversal will give +/- .02, occasionally better, assuming that the operators does the right things. The drum system with and eccentric wheel which gives later agitation as well as rotation is much because it tends to give streaky processing.

I wish I could describe the "Dobro" method that we Brookies had to learn from our mentor, Boris Dobro in the 1940's through the 1960's, it gave the best hand processing in a stainless steel reel/tank system, I could show you but I'll be darned it I can describe it in words even though it is actually simple. It yielded +/- .03 (1/10th f stop) in a unimaged 1.00 density.

At Calumet in the old days when the company actually manufactured things, we guaranteed density variation of +/- .02 sheet to sheet and film to film, 1/10th of the so called standard. For special uses with special temperature controlled processes, we would guarantee +/- .10.

I did research on these systems and of course the very best was motion picture spray processing which was +/- .01, or 1/30th of an f stop variability, we did a still version of these for TV shadow masks, and sensitometric processors (which we also made).

Lynn

I also wonder what the effects would be for stand development like I use with Pyrocat. The level of agitation is so minimal, I have a tendency to believe a constant rotation might reduce edge effects and overall effectiveness of the solution.

Often, continuous agitation is not what I want. And I do not have any quality problems with Ilford-style inversion agitation, including some gentle rapping on the edge of the sink. That is almost always the way I process my films.
The fact that people sometimes cock up agitation (or can't load film reels, or can't master exposure, or can't stay on a bicycle) does not necessarily mean that the world needs to search for a solution. Often it just suggests that a bit of patience and practice is required.

Ian

David Lyga said:

How? I fill the tank only half full with developer. Then, I immediately turn the tank on its side and begin rotating it throughout the development time. This absolutely guarantees that no film area will be left behind in the consistent development process. (Consistency is a must because development is most always NOT done to completion, unlike fixing.) I find that using a water bath to rotate the tank in is best for two reasons: first, it is easier to rotate because the tank becomes lighter in water and, second, because I believe that the solution actually gains a few degrees in temperature, probably because or the reaction involved.

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That's almost exactly how I did C-41 and E-6 process before I made simple motorized rotator.
I put the paterson or Jobo 2500 serie tank on the water bath on it's side and gave rotation by hand.

Later, I build simple processor that uses same technique. The tank floats on the water bath and is rotated by wheels that supports and presses the tank against water's buoyant force.
Sample video on youtube: http://www.youtube.com/watch?v=suQTE3wx_Jk

That's the more interesting and promising DIY processor I've seen so far. How do you disengage the wheels to take the tank out of the water?

Diapositivo said:

That's the more interesting and promising DIY processor I've seen so far. How do you disengage the wheels to take the tank out of the water?

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No need to take wheels out as the tank can be turned proper position under the water and lift out between the axles.

With the long paterson tank it's bit difficult, but smaller tanks (2x 120 etc) it's very easy.