If this could be made to work it would have the same appeal as nitrogen burst agitation, i.e. you could just start development and go away and let the magnetic stirrer do the agitation. The key would be to induce some kind of random pattern in the flow of the eddies. There are a number of potential problems but with some thought there is certainly a possiblity that it could be a practical system of development.Originally Posted by Vaughn
Sandy King
"If this could be made to work it would have the same appeal as nitrogen burst agitation, i.e. you could just start development and go away and let the magnetic stirrer do the agitation."
This is also true of some of the rotary pocessing equipment.
I am still trying to figure out what it is about either trays, hanger and tanks, rotary proessing, or gas burst that magnetic agitation is going to solve.
steve simmons
I dunno. It was just a thougt -point is that there's a way to get the liquid to move using magnets as the basis of an agitation system. I am doing the "big picture" thinking, and let the details to be worked out by others.
Magnetic fields would not affect negs.
It's not the magnetic fields, it's due to the regular currents that these make while stirring.
Greg Lockrey
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Compared to nitrogen burst, you don't have to keep paying to get your nitrogen bottles refilled. This would really be applicable only in deep-tank systems where nitrogen burst is now used; magnetic stirring in trays would be very prone to scratching negatives, while rotary processing already has agitation built in. Any system where you can reduce an ongoing cost has an advantage, over time; magnetic stirring drivers aren't free, but they last decades with virtually no maintenance, while the magnets that go in the liquid are relatively cheap (and could be made easily and still more cheaply with epoxy resin and common bar magnets, so no need to pay lab equipment prices).
The trick is to avoid the systematic flow cells that continuous magnetic stirring will tend to set up, and the key to that is probably a combination of reversal, multiple stirrers, and intermittent stirring. Use of an agitator that isn't the classic "horse capsule" shape might help, too -- picture an agitator shaped like the aluminum base plate of the small flying fireworks that were commonly sold before "Safe and Sane" took over the world: a disk with fan blades pressed in. Make one of those from stainless steel, attach a bar magnet with chemically inert epoxy (fully enclosing the magnet) and you'd have a stirrer that generates a primarily upward-directed flow. Same thing with vertical blades instead of angled, and you get down-and-out flow. Alternate between driving, say, three of one and three of the other in the bottom of a 3-gallon tank, with rest periods between, and you'd have agitation that might begin to simulate nitrogen burst (or you might find out you're better with half a dozen of the upward sort).
The first fellow who tries this will spend some money and a fair amount of time in the dark getting it right. Then, however, he'll be able to sell it as an alternative to nitrogen burst that will make a line using the magnetic method cost less to operate than nitrogen burst -- and thus more profitable over some long term.
If a contact print at arm's length is too small to see, you need a bigger camera. :D
Paying $15 every other year (or longer) for 65 ft3 of nitrogen is really not a major expense in the larger scheme of things. I know folks that process fairly regularly with N2 burst and have used the same nitrogen tank for nearly three years.
But at the end of the day what is important are the results that any process accomplishes with your negatives relative to consistancy, ease of use, system maintenance costs and operational flexibility. Cost effectiveness needs to be considered, but this variable should be looked at over a reasonable period of use say 5 + years. All I know is that with a JOBO system I am concerned about replacing pumps, gears, tanks and other moving parts that will eventually wear out. With a gaseous burst system the only moving part is the solenoid valve and Ansco claims that they have been tested for years of use with no noticable degredation of effectiveness. That and the long standing history of producing negative to professional standards is what got my attention with this system and to study it further.
Compared to rotary processing the difference is that both nitrogen burst and magnetic stirrer systems offer the possibility of even development with very reduced agitation. Reduced agitation gives slightly greater effective film speed (desirable) and greater adjacency effects, which can increase apparent sharpness (also desirable).
There are a number of practical obstacles to overcome but I believe there is a lot of potential in a system based on magnetic stirrer, as there clearly is in nitrogen burst systems.
Sandy King
OK, I will wait and open my mind for future possibilities.
steve
Lots of ideas are unworkable until someone comes along and figures a way to make it work. I guess that is why we have this magical thing called photography!
vaughn
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