Hi,
I am designing a system to develop very large format prints (about 1x2m).
I already have four 130x65cm trays in my darkroom and they take up the whole room. So I thought about a rotary system.
My idea is to use a sewage PET tube (they are very thick and solid and sell in many sizes) and a dual chamber tank.
The tube (~40cm ø) should be held by custom built stainless steel clamps, probably fixed to the tube by means of steel screws, and converging to a hub (sort of a bird's paw shape). The clamps are held by two metal tripods or similar and they can rotate by means of bearings.
The tank should have one partition where chemicals are poured and then dumped, and another with constantly running water. Each partition would be large enough to soak less than half of the tube in the chemical/water. It should be slightly larger than 1x2m. The bottom of the tank has a slope and a fairly large tap at the end so the chemicals can flow out easily. The tap in the water tank is left slightly open so the chmicals and byproducts, heavier than water, are flushed by the bottom. the whole tank is raised so a bottle/container can be put below it to collect the flushed chemicals.
If the tank has a metal frame it can have two pairs of U-shaped dents on the top edges, where the hub of the tube can sit, thus eliminating the need for tripods.
Processing:
- The drum is put in the empty half of the tank, while the other is filled with water.
- Developer is poured in and the drum is spun by means of a motor or (poor/lazy man's solution) a crank.
- Developer is dumped back to its container. Since this can take up a while, the drum is transferred to the water tank, which rinses the developer off the print in the meanwhile.
- The chemical tank is rinsed and flushed.
- This process is repeated for each step of stop, fix, hypo clearing etc. following the useful advice on LLoyd Erlick's single tray method: http://www.heylloyd.com/technicl/single.htm
- The print is taken out of the drum and dried.
Advantages of this method:
- You can achieve archival quality by using as many developing/fixing/clearing steps as you need, using the minimum space
- Print is rinsed after each step so the chemicals are not contaminated
- the drum does not touch the bottom of the tank, so the "dirty" water in the water tank is flushed by the bottom, and the print receives fresh water from the top.
Problems:
- A drum this size is very heavy and large. The main issue is to lift it over the tank edge and put it on the other tank, and then back for each step. To do this you either need an assistant, or a mechanical system to lift the drum. I have thought about two steel ropes and pulleys attached to the ceiling, but it seems too complicated
- Taking the wet print out of the drum. A solution coud be using a thick plastic sheet to hold the print, like in some Jobo drums. What is dreadful about this, though, is that if you are not careful enough, a hard edge of the plastic sheet can touch the wet print while you are taking it out, and scratch it.
- Will the back of the print be rinsed adequately? Ridges shoud be added to the above mentioned plastic sheet, or a separate tank can be built outside the darkroom just for the final rinse.
- One of the clamps should be screwed in before developing and taken off after rinsing. A simpler solution might be found.
I would appreciate some feedack, and hope this can insipre somebody else.
I like it. It could be simplified by just having one tank and the ability to pump developer, fix, etc. in and out back to their individual containers with a rinse step in between.
It could all be gravity fed instead of pumped but at some stage you will need to transfer the chemistry from the low level storage back to high level. Perhaps use pumps for this.
EDIT: Some of the text isn't clear on my drawing but I think it's self explanatory. Tanks of processing chemicals above the main tank which can be emptied into the main tank using the taps. When the stage is over, the chemistry can be emptied into the receiving tank at which point a pump with a level switch transfers it back to it's holding tank for next use.
Taps also included for filling with fresh water and emptying to a drain.
Steve.
Last edited by Steve Smith; 03-04-2010 at 03:12 AM.
gattu marrudu,
the disadvantage of your system is that it is quite bulky (in case I got the idea behind it right.
Have you considered a reel-to-reel system as the one Deville of France once offered? Of course then you have the issue of reel-to-reel processing with a rather static layer of processing bath between the windings.
Pumping out is a great idea. It would reduce the tank size by a half and save my spine! I would use pumping only to force the chemicals out (especially developer) as quickly as possible though.
Your system has the advantage that it keeps only one type of liquid in each circuit, keeping them cleaner. But, since I would use more steps in my process (dev - stop - fix 1 - fix 2 - hypo clearing - eventually toner) that would not be very practical. And I would just pour the chemicals in from their tank, and pump them back out to their tank so I don't need a lot of tubing.
What is a reel-to-reel system?
gm
Last edited by gattu marrudu; 03-04-2010 at 03:57 AM.
The system you've devised is clever but impractical as the print will end up severely crimped when you spin your drum. Wet FB paper is like a wet noodle. With a drum diameter large enough to fit a 3-4 ft. wide piece of paper so that the paper does not overlap the paper will collapse on itself as soon as it gets wet. The only way this might work is if you spin the drum at high enough rpms to introduce centrifugal force sufficient to keep the print pressed up against the inside wall of the drum. And at that point you still have the problem of removing the print from the drum without destroying it.
Processing prints this size is best done in narrow troughs with the print being scrolled through about a gallon of working chemistry.
I remember watching a video of a guy that had an UULF camera made on a trailer. IIRC the resulting positives were about this size. He used a piece of drain pipe that looked about 30-40cm diameter and rolled it around on the floor. It was a color process so the paper may have been RC.
@mhulsman, about rollerskates: why simpler? I would have to take care of 16 bearings (2 per skate wheel) instead of 2; and they would be sunk in chemical/water, getting rusty and polluting the water with their oil+dirt.
@frotog: You got a point there. I might add some clamps inside the tube, all along both of the wrapped edges to keep them stuck to the surface; but that might not prevent the center from falling down, even on heavy weight paper. Spinning too fast would make a splashy mess. An alternative would be using 300g watercolor paper with liquid emulsion, or your method; a whole different approach but still worth exploring.
Let me think about cranks and chains and other torture instruments...
I think that the drum you envision for a print 2 metres long will be unmanageable due to weight alone. Handling time could be an issue in an elaborate system. I am designing a drum for 760mm x 1200mm film and with 3 litres of chemistry will weigh over 30 pounds. That is for 3mm plastic wall thickness or stainless steel for the drum body. You say you have trays that are 65cm wide which would be still very functional if they were reduced to half that width. They would then take up half the space. I have hand processed hundreds of large prints by rolling the paper back and forth without problem.
Richard
Why are there no speaker jacks on a stereo camera?
If you're intent on making some kind of machine to do this the solution suggested by Agx is the most logical. Never having seen one of these Deville machines I'm envisioning a mechanized version of the traditional scrolling technique. After exposing the print you could secure the leading edge to the outside of a dowel or tube and then roll the paper around the outside of the cylinder, emulsion side facing in. Then drop the cylinder with the print wrapped around it into your trough and secure the opposite leading edge to another cylinder. If the two cylinders were held secure in some kind of frame you could hand crank the paper back and forth through your chemistry. Still seems like a rube goldberg solution to a rather simple technique though.
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