miNox Tank Agitation method

Discussion in 'Minox' started by mtc photography, Dec 20, 1998.

  1. Agitation of MINOX Tank
    • Agitation with Minox thermometer-for regular B&W film / regular strengh developer
    • Recyling Agitation with eye droper- for copy film
     
  2. Agitation with Minox thermometer

    For regular strength developer from 1:1 up to 1:15 dilution, the standard agitation method for Minox tank is the thermometer pumping method.
    Put the thermometer in the center well of Minox tank, and gently move the thermometer up and down, like a pump. You can see the developer level rises and fall at the snout. The thermometer displaces about 2-3 ml of liquid.
    If you have a Minox tank without thermometer, you may use a baby medicine droper, which fits into the thermometer well to pump the developer.
    Be careful,don't push the thermometer too hard, otherwise you may break either the thermometer or the tank.
    How "Thermometer Pumping" works in Minox Developing Tank
    The following is a cross section of the Minox daylight development tank
    T -- the thermometer well
    C - the coil holding the film
    When the coil is put into the tank, it divides the liquid container into two concentric cylinder partitions, one outside of the coil, denoted by 'O', the other inside the coil denoted by 'i'
    The clearance of the 'O' partition is 7.2mm The clearance of the 'i' partition is 2.3mm
    Which are derived by the following measurement with a caliper.
    • Inner diameter of tank : 46mm
    • Outer diameter of coil : 38.8mm
    • 'O' clearance: : 7.2mm
    • Inner diameter of coil : 35mm
    • diameter of core : 32.7mm (at film grove)
    • clearance: : 2.3mm

    • ( diameter of thermometer hole: 8.0mm )

      C C
      || || || ||
      || || T || ||
      || O || i i || O ||
      || || // \\ //\\ || ||
      || || || || || || || ||
      || || || || || || || ||
      || || || || || || || ||
      || || || || || || || ||
      || || || || || || || ||
      || || || || || || || ||
      || || || \\// || || ||
      || || || || || ||
      || || || || || ||
      || || || || || ||
      || || || || || ||
      || || || || || ||
      || || || || || ||
      || || || || || ||
      || || || || || ||
      || || || || ||
      || || || ||
      ||========|| ||========||
      Because of the two partitions are separated by a coil, liquid cannot flow freely from the inner partition to the outer partition or visa versa in a horizontal manner.
      Instead, liquid is forced to flow down the narrow inner partition, to the bottom of the tank, than flows to the bottom part of the outside partition, then up.
      There are two triangular shape cut out at the bottom of the core, plus a 3.4mm round hole at the bottom of the film grove to facilitate the flow of between to two partition; all these three 'deep channels' are at or near the bottom of the tank.
      The following diagram illustrate pouring developer into the center of the tank (T)
      1) The developer fills up the 'thermometer well"
      2) liquid overflow the thermometer well, then flow DOWN the inner partition, to the bottom of the tank, passing through the three "deep channels at the bottom of the oil, then flows back UP along the outer partition. 3) Until the liquid is at same level
      Pouring developer

      *
      *
      *
      *
      *
      || || * || ||
      || || * * * * * * * * * || ||
      || || * * * * * * * * * || ||
      || || * // \\ * //\\ * || ||
      || || * || ||* || || * || ||
      || || * || ||* || || * || ||
      || || * || ||* || || * || ||
      || || * || ||* || || * || ||
      || || * || ||* || || * || ||
      || || * || ||* || || * || ||
      || || * || \\// || * || ||
      || || * || || * || ||
      || || * || || * || ||
      || || * || || * || ||
      || || * || || * || ||
      || || * || || * || ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * * || || * || * ||
      || * * ** || || * * * ||
      ||========|| ||========||



      Developer filled.



      || || || ||
      || * || * * * * * * * * * || * ||
      || * || * * * * * * * * * || * ||
      || * || * // \\ * //\\ * || * ||
      || * || * || ||* || || * || * ||
      || * || * || ||* || || * || * ||
      || * || * || ||* || || * || * ||
      || * || * || ||* || || * || * ||
      || * || * || ||* || || * || * ||
      || * || * || ||* || || * || * ||
      || * || * || \\// || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * * || || * || * ||
      || * * ** || || * * ** ||
      ||========|| ||========||


      PUSH IN thermometer RAISES the fluid level of inner partition
      forcing fluid to flow down the INNER partition to to bottom of
      tank then flow backup through OUTSIDE partition.





      T
      T
      || || * * * * * T * * * || ||
      || * || * * * * * T * * * || * ||
      || * || * * * * * T * * * || * ||
      || * || * // \\ T //\\ * || * ||
      || * || * || || T || || * || * ||
      || * || * || || T || || * || * ||
      || * || * || || T || || * || * ||
      || * || * || || T || || * || * ||
      || * || * || || T || || * || * ||
      || * || * || || T || || * || * ||
      || * || * || \\ // || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * || * || || * || * ||
      || * * || || * || * ||
      || * * ** || || * * ** ||
      ||========|| ||========||


      PULL OUT thermometer lower the fluid level of inner partition forcing fluid to flow down the OUTER partition to to bottom of tank then flow backup through inner partition. Thus pushing down the thermometer, causes the developer to flow up along the film groves, and pull up the thermometer, causes the developer to flow down along the film grove. In spite of the seemingly minimum movement of the thermometer, it actually provide effective agitation for developer. From here we can see Walter Zapp's ingenuity in the design of the Minox daylight development tank.
     
  3. Agitation for highly diluted developer

    When highly diluted developer (such as 1:50 to 1:100 ) is used, the thermometer pump agitation method is inadequate. The resulting negative is too thin, hardly printable. This is not because of the chemicals in 55cc of highly diluted developer is not enough, it is because of the devloper in the Minox tank has not being fully utilized.
    Test the effectiveness of thermometer pump with ink drops

    This fact can be easily check out by using 55cc of clear water in the tank, drop 3-4 drops of blue ink in the center well, followed by thermometer pumping, then use a Q-tip to take water sample off the snout and put it on a piece of white paper at 1 minute interval; you will find out that at the beginning, the water marks are colorless, the next few samples beome deeper in blue; it takes a long time before the water sample marks on the paper get even, indicative of the fact that the pumping action does not recycle the fluid effectively.
     
  4. How liquid flows inside the Minox Tank

    Why the developer in Minox tank is hard to mix ?
    Take a look at the interior of Minox tank with the helix coil removed.The tank looks like a enlongated cake pan with a center post. Pour 55 cc of water in it, you will see the liquid forms an O shape around the ceter post. Now put in the helix coil; you can see the liquid in the tank is now divided into two partitions, one out side partition where the film is, and an inside partition containing the thermometer well and the gap between the coil and the center post of the tank. The liquid in these two partitions is connected only throught the bottom of the tank. When you push the thermometer down, the liquid in the inner partition flows down through a notch at bottom of helix coil, then flows upward to the outside partition, passing the film emulsion surface, then to the snout. When you pull up the thermometer, the liquid flows in the opposite direction, like a seesaw. Since these two partitions are very narrow, you can imaging, the fresh developer in the center partition has hard time mixing throughly with the used developer at the film partition
    . The developer in the film area accounts for only about 20cc, roughly only a third of the total volume of developer. If the other two third of developer stays inside, it never get used. The end result is that only 1/3 of the chemical in 55ml of developer is used. That is certainly too little, that is why the negative developed with highly diluted developer using thermometer pump is underdeveloped. In the part, people concluded that Minox tank is no good for highly diluted developer.
    We know now that this is not true.
    How to make the fresh developer reserve stored in the inner partition comes out and mixes thoroughly with the used developer at the outer partition ?
    Developer Recirculation
    My method is to use a baby medicine droper( the 3 to 5 ml ones you find in corner pharmacies ) to get about 2-3 ml developer from the snout and drop it into the center well. That is my technique of eye droper recycling. Ink test shows that eye droper recycling method mixes up liquid very quickly, hence the full 55 CC of developer, even highly diluted ,is utilzed to the full.
    Use an medicine droper to recycle developer from snout to center well.



    * ** ** ** ******** from snout
    * *
    to center well * *
    V || ^ ||
    || * || * * * * * * * * * || * * * * * * ||
    || * || * * * * * * * * * || * * * * * * || snout
    || * || * // \\ * //\\ * || * * * * * * ||
    || * || * || ||* || || * || * ||=========
    || * || * || ||* || || * || * ||
    || * || * || ||* || || * || * ||
    || * || * || ||* || || * || * ||
    || * || * || ||* || || * || * ||
    || * || * || ||* || || * || * ||
    || * || * || \\// || * || * ||
    || * || * || || * || * ||
    || * || * || || * || * ||
    || * || * || || * || * ||
    || * || * || || * || * ||
    || * || * || || * || * ||
    || * || * || || * || * ||
    || * || * || || * || * ||
    || * || * || || * || * ||
    || * * || || * || * ||
    || * * ** || || * * ** ||
    ||========|| ||========||
    I usually prepare 60 CC of diluted developer, for example, 1 cc or Rodinal Special + 60 CC distilled water to develop Agfapan APX 25 8x11 film (42 exposures ).
    For Techpan, I use 1 cc Rodinal Special + 80 cc water, in 1:80 dilution; 55 cc initial pour, recyle the developer with baby droper, at midway point 7.5 minute, add new develper from the remaiing 25 cc (80-55) into the center well of tank, let uused developer flows off snout. This is recyling + replenish method. I have since developed about 80 rolls of Minox BW film, mostly techpan, with highly diluted develper in Minox tank.
    Some of my Techpan film was even developed with only 0.7 cc Rodinal Special +60 CC diluted water ! I don't see visible difference between 0.7+60 or 1cc +80cc. Rodinal is so cheap, I use 1+80 cc as my standard procedure for Techpan.
     
  5. I find that a rubber syringe/bulb, like that used to aspirate
    children's stuffy nose is extremely handy for agitation. Just put the
    snout in the thermometer hole and cycle pushing/releasing, while
    holding the bulb in to seal the opening. It works like hydraulics. You
    can control agitation speed and pressure easily.
     
  6. For development of very fine grained, high contrast "doku"-material
    such as TechPan or the Fuji HR a more smooth development
    can be archieved with this agitation scheme: strong agitation for
    a short time (e.g. 10 sec) and no agitation for the rest (e.g. 50 sec)
    For this, the following technique works well:

    <p>

    from a baker with 100 ccm developer solution
    the tank is filled, then, for agitation, every minute
    I poured out about 20 ccm of the developer from the tank back into the
    baker, then filled up the tank again from the baker. This can be
    done in about 8 seconds. With this technique,

    <p>

    -more developer than the 55 ccm can be used
    -a strong agitation is asured
    -and a good mixing of the solution inside the
    tank is asured.

    <p>

    The results are looking fine
     
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    References on Agitation of Minox Tank







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