miNox Tank Agitation method

MTC Photography · December 21, 1998

<TR>

<TD><center> Agitation of MINOX

Tank </center></TD>

</TR></table></center>

<ul><LI>Agitation with Minox thermometer-for regular B&W film / regular strengh developer

<LI>Recyling Agitation with eye droper- for copy film</ul>

MTC Photography · January 15, 1999

<h3>Agitation with Minox thermometer </h3>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.

<h3> How "Thermometer Pumping" works in Minox Developing Tank</h3>

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.

<ul>

<li> Inner diameter of tank : 46mm

<li> Outer diameter of coil : 38.8mm

<li> 'O' clearance: : 7.2mm

<li>

<li> Inner diameter of coil : 35mm

<li> diameter of core : 32.7mm (at film grove)

<li> clearance: : 2.3mm

</ul>

 ( diameter of thermometer hole: 8.0mm )

<pre>

C C

|| || || ||

|| || T || ||

|| O || i i || O ||

|| || // \\ //\\ || ||

|| || || || || || || ||

|| || || \\// || || ||

|| || || || || ||

|| || || || ||

|| || || ||

||========|| ||========||

</pre>

 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

<pre>

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 || || * || * ||

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

|| * || * || || * || * ||

|| * * || || * || * ||

|| * * ** || || * * ** ||

||========|| ||========||

</pre>

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.

MTC Photography · January 15, 1999

<h3>Agitation for highly diluted developer</h3>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.<h3>Test the effectiveness of thermometer pump with ink drops</h3>

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.

MTC Photography · January 15, 1999

<h3>How liquid flows inside the Minox Tank</h3>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 ?<h3>Developer Recirculation</h3>

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. <pre>

Use an medicine droper to recycle developer from snout to center well.

* ** ** ** ******** from snout

* *

to center well * *

V || ^ ||

|| * || * * * * * * * * * || * * * * * * ||

|| * || * * * * * * * * * || * * * * * * || snout

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

|| * || * || ||* || || * || * ||=========

|| * || * || ||* || || * || * ||

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

|| * || * || || * || * ||

|| * * || || * || * ||

|| * * ** || || * * ** ||

||========|| ||========||

</pre> 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.

gary__1 · July 16, 1999

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.

oliver__ · November 19, 1999

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:

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,

-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.

The results are looking fine

MTC Photography · September 10, 2000

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of

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