ABS Developing Tank

[jharr]

I am a complete darkroom noob, so forgive me if I am overlooking obvious flaws here. This probably falls into the "solving a problem that doesn't exist" category, but that is where a lot of my DIY projects start. I have read about the 'taco' method of developing 4x5 sheets in a roll film tank and it seems that the main problem people run into is some sort of banding caused by the elastic hair ties used to hold the 'tacos'. There is the paper developing tube method which seems to work, but seriously?? $691 for a Jobo tube??? Numbers like that jolt my inner skinflint to life and I start designing the same thing for 1% of the cost. Really, it's a tube with some sort of mechanism to hold sheets of film. I took a couple of drinking straws and cut them to about 5" length and then cut slots down the length so if you are looking at the end it looks like a "C". Then I glued the straws inside a 12" length of 3" ID black ABS so that the open sides are facing each other about 4" apart "c______ɔ". Slide the film into the gaps in the straws and it holds it just fine without touching the inside of the pipe. Do two sets of these on each end and you can hold 4 sheets. It doesn't matter (as far as I can tell) which way the emulsion side faces. You can then use regular rubber end caps with screw clamp fittings to seal it up and use a roller motor or whatever agitation method you want (floating a la BTZS). It isn't as convenient as a 'daylight' tank with a light trap, but again, convenience costs $691.

J--

[Leszek Vogt]

It sounds good in theory. Wonder if I could apply your idea to larger dia ABS....using 5x7 film. Does that call for a fresh patent ? Can you show us some pics ? Thanks.

Les

[jharr]

Ok, here is the tank with the 'inner tube' inserted using a couple and an end cap as described above.


This is the open end.


Without the inner tube so you can see the straws better.


Here it is with a sheet of film inserted. You can see that the film does not touch the inside of the tube.

[polyglot]

Doesn't look like you'll get much flow into the area between film and outer tube, so I definitely think you want to load it emulsion-in. Have you tried it to see how even your development is or whether you get flow marks? What purpose does the inner tube serve?

And no one pays $700 for a Jobo tank unless it's a rare 3xxx series. You can get a 2509 insert and matching tank for well under $150. I paid about $250 for my 3010 but I agree, that is a lot for a fancy plastic bucket.

[jharr]

polyglot, I haven't tried it yet. There are a few more things to do before I use it. I need to plug the end of the inner tube and figure out a 'guide' system that will keep it centered. The inner tube is there simply for volume consumption. Without it, the tube holds 2.7L, with it, it holds just under a liter. So if you are doing constant agitation, you don't need it and can use a small volume of developer. If you are doing stand development and don't want to use 2.7L of chemistry, then the inner tube helps with that. A Peterson tank only uses 500mL, so the taco method is probably still the more economical way. Again, the only problem this solves is the potential for 'banding' from the taco holders. We will see if it introduces other problems.

[Rick A]

I found that soaking the fixed film sheets for an extra minute in a tray of fixer removes the "banding" imprint. When my timer rings that I'm finished with the fixing phase, I dump the fixer into an 8x10 tray, then remove the bands from the film and place the sheets into the tray. I can see when the marks disappear and know when to wash.

[Light Guru]

There is the paper developing tube method which seems to work, but seriously?? $691 for a Jobo tube???

There are tube options that are a LOT cheaper.

Look into the unidrum and the unidrum motor base.

I dont think your inner pipe is going to let the chemistry move around enough, it would be better with out it.

[jharr]

There are tube options that are a LOT cheaper.

Look into the unidrum and the unidrum motor base.

I'll look into it. They don't seem super abundant after a quick search.

I dont think your inner pipe is going to let the chemistry move around enough, it would be better with out it.

The inner pipe is intended to reduce the volume when doing stand development in which case still chemistry is desirable.

Thanks for the input everyone. For the VERY small investment I have into this, it will be fun to try. I always like to see if something simple can do as good a job as something engineered and mass-produced.

J--

[Light Guru]

The inner pipe is intended to reduce the volume when doing stand development in which case still chemistry is desirable.

If you put it on a motorized base to rotate it you don't have to fill the whole tube full of chemistry. In addition the rotary base provides consistent agitation every tie you develop.

Also you don't have to hold the film up away from the side of the tube because film only has emulsion on one side (if you are shooting x-ray film then it does have emulsion on both sides)

Have a look at this article about processing in the unidrum.
http://www.largeformatphotography.info/unicolor/
it has some images of the inside of the drum to help you see that it could be simpler then the straw with a slit to hold the film.

The hardest part you face is getting a light tight container that will let chemistry in and out.

if you want to do simple developing in tubes check out how the BTSZ tubes work.

[jharr]

If you put it on a motorized base to rotate it you don't have to fill the whole tube full of chemistry. In addition the rotary base provides consistent agitation every tie you develop.

I'm not being clear. For regular drum development on a motorized base, yes, the inner tube in unnecessary and 300-500mL of chemistry is adequate. However, with stand development (Rodinal 1+100 or Caffenol-CM) there is just 30sec of agitation followed by around an hour of just sitting there. During this hour the film must be submerged. So instead of filling my drum with 2.7L of chemistry, I put a tube down the center to displace most of the volume. This means that I only need about 1L of chemistry to keep the film submerged. So I may or may not use the inner tube, depending on what kind of development I am doing. If I don't use it, I would just have flat end caps on both ends and would probably float it like a BTZS tube. The BTZS tubes seem a little fiddly to do 4 or more at a time.

Also you don't have to hold the film up away from the side of the tube because film only has emulsion on one side (if you are shooting x-ray film then it does have emulsion on both sides)

The reason for having a gap between the film and the side of the drum is to make sure that the antihalation layer is completely washed away. This is one problem some have with the cloth bungees used for the taco method, though as ralnphot pointed out, a final tray wash can ameliorate that problem. For me, less film handling is better because I am clumsy.

J--