Agitation - hand - small tank

Discussion in 'B&W: Film, Paper, Chemistry' started by fhovie, Mar 14, 2005.

  1. fhovie

    fhovie Subscriber

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    I read a lot of posts wherer people talk about gentle agitation. I don't understand where this comes from. From a mechanical point of view, developer contacts the film, it becomes exhausted. Gentle agitation washes over the laminar layer of exhausted developer and slightly increases its activity. A rapid violent agitation will strip away the laminar layer of exhausted developer and contact the emulsion with fresh developer. I HAVE NEVER HAD STREAKS using this kind of agitation. That includes a combination of AGFA - KODAK - ILFORD films and D76 - D23 - PMK - Pyrocat - PC-TEA - MYTOL - Di-Xactol -including pushing - pulling and every combination you can think of in all formats from 16mm to 4x5.

    Intrinsically, the gentle agitation doesn't make sense to me. How is it superior to not want to rip off the laminar flow of exhausted developer in a short violent act? My agitation is - after a water presoak of one minute approx - add developer and do 30 seconds of agitation by (semi) rapid inversions followed by tank (1/4 turn in each direction) spinning - this allows the motion to be in varied directions. I do not try to get the chemical to accelerate such that it will cause overdevelop banding near the spool edges. Just 180 degree motions that allow the air in the tank to burst across the film breaking up pockets of exhausted developer allowing fresh developer to do its job. This is usually 2 complete inversions back and forth with one or two 1/4 turn spins and a tap or two setting it down to break loose any bubbles that may have caught. The whole cycle takes 5 seconds or less - and I do it every 30 seconds - All my times are calibrated for this type of agitation and I get reliable grade 2 for condenser enlarger density ranges. Of course I am not suggesting that my way is the right way or that anyone should do anything different - I am just wondering where the gentle agitation idea comes from.
     
  2. Mongo

    Mongo Member

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    Your method of agitation sounds very much like mine. I always assumed that "gentle agitation" was suggested to stop people from picking up the tank and shaking it like a salad dressing bottle. I've never tried shaking a tank that way, but I imagine that the risk has more to do with actually buckling the film or dislodging the spools than with the flow of the liquids.

    Just my thoughts...
     
  3. titrisol

    titrisol Member

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    I have used the shaking method, toroidal method and spindle method.
    Haven't found much differences between them.

    I believe a toroidal moement is enough, but I prefer to shake the tank at the beginning.
     
  4. kaiyen

    kaiyen Member

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    What you do is what I do, and that _is_ what I consider to be "gentle" agitation. I do two inversions with about a 1/4 turn in 5 seconds, with one hard rap as I put the tank down.

    However, keep in mind that many beginners agitate the heck out of tanks. When I first took photo 1 (not that long ago...) I agitated maybe 10 times in 5 seconds (!). I was told that agitation kept the developer moving, and that was a good thing. So more inversions was better, right?

    _And_, most importantly, I saw a lot of others in my classes doing the same thing. I think it's those situations in which "gentle agitation" is an accurate recommendation.

    allan
     
  5. Digidurst

    Digidurst Subscriber

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    I can see the thread now...
    "I've just splashed developer all over my kitchen because I shook the devil out of my tank. The tank is no longer possessed but do I need to call a HazMat Team in to deal with mess?"

    Tee hee hee
     
  6. fhovie

    fhovie Subscriber

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    Haz Mat? - I use vitamin C developer and drink it when I am done - of course that would explain a lot ....
     
  7. jcausey

    jcausey Member

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    I go for a mixture... the actual inversion is a sudden, almost violent movement designed to break the developer's surface adhesion, but the subsequent rotation is more gentle.
     
  8. Blighty

    Blighty Subscriber

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    I use an 'invert and twist' technique. Four inversions with a sharp twisting action on each. Works well for me. BLIGHTY
     
  9. Soeren

    Soeren Member

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    I invert the tank 180 degrees 5X in 10 sec, each inversion taking 2 sec forth and back.
    I do this every third minute thus adding 10-30% to the devtime depending on the contrast wanted. The agitation is one of the most important variables to the final result, so it is more important to be consistent than how violent you do it. I do however feel that the gentle timed inversion are more easy to replicate from time to time than the more violently agitation.
    Any one else using minimal agitation ?
    Regards Søren
     
  10. Ed Sukach

    Ed Sukach Member

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    Like all things photographic, I don't think there are hard and fast, concrete, ne varietur rules. LOTS of agitation - the more, the better, is not automatically and without exception, a good thing. There is something called the "compensating effect" where exhausted developer in immediate contact with the more exposed areas of the film will have less activity, while that on the less exposed areas will still be active - at times, a desirable effect. That effect is limited, though, and some agitation will be necessary to refresh and re-start the process. Such is the value of stand development ... highly diluted developer for an extended period of time with "not much" agitation.

    Agitation patterns are, in short, another tool in the box.
     
  11. Donald Qualls

    Donald Qualls Member

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    Your method is very similar to mine -- five inversions, with a pass from hand to hand that inserts a bit less than a quarter turn in each inversion, taking between 10 and 15 seconds. One cycle like this every 3 minutes (after constant agitation the first minute), using highly dilute developer (and contrast control through more or less frequent cycles of the same agitation method, rather than a change in time). I've gotten things figured out so I can use the same method for film from 16 mm through 35 mm and 120 and up to 4x5 (in daylight fill tubes). Gives nice smooth negatives with good shadow detail at box speed, but (with the time added for reduced agitation and dilute developer) takes a long time...