THE ADDIS SPACE MAKER STORAGE BIN
By The Rev`d Ronald Hatful (Area 9)
The `Addis Spacemaker Storage Bin` is one of a series made by Addis and are simple rectangular plastic bins.
The one I have has internal measurements of appx. 45cms long, 30cms wide and 18cms deep. It has a total capacity of nearly 25 litres and a working capacity of 18 litres. The depth is just right for the normal 600ml glass bottles and the 300ml glass bottles that I can get from the local chemist shop. They are available in a variety of colours.
I fill it with water at near 38C and let the UNO Thermostat take care of things.
For agitation, I have rigged up a stirrer rather on the style of a laboratory stirrer but made from bits and pieces that I have hoarded for years. The paddle is a paint stirrer that was intended to be used with an electric drill - but they were withdrawn after people complained that they threw paint all over the room! I have fitted it to a 24 volt motor that was originally fitted to a large aero camera, purchased at the end of the war for œ10 complete with a 7" F2.5 Ektar lens. The speed is rather too high at 24 volts from a transformer, but reducing it to 12 volts is fine.
The developing tank for a single film stands on a shelf bent up from sheet lead - I just happened to have the lead but it has the advantage that it`s weight keeps it in place!.
The procedure that I used so far is to wait until things have established - this I judge by the temperature of the first developer in the bottle standing in the bath. I then begin by giving the film a pre-soak with water plus a few drops of wetting agent, at 41C for about 1 minute.
The pre-soak water is discarded and the First developer added to the tank. Agitation is by inversion and the temperature in the tank is checked at the half-way point, although I have yet to be convinced that an accurate reading of temperature can be obtained with an ordinary thermometer because of the very small bulk of developer inside the central column of the spiral.
If the temperature is found to differ from 38C then the time of the development is adjusted to compensate. In my experience the temperature is usually down by half a degree - due I suspect to the developer coming into contact with the lid of the tank and which is exposed to room temperature.
Experiments with temperature control will continue - I intend to get one of the Maplin thermometers and see if I can calibrate it accurately.
COMMENT
Reverend Hatful makes an interesting point in regards the "actual" temperature in the centre of the developing tank, and one that has been raised many times over the years. A couple of points have to be considered - one that the volume of water/chemical in the centre of the tank is very small, and secondly - when you dip a cold glass thermometer into it, there will be a drop in temperature due to absorbtion, hence the feeling of inaccuracy! Perhaps warming the thermometer by half a degree or so may correct this, but whatever you do, it leaves an elliment of doubt.
My experience on this is very limited. However last year while getting to grips with using a pH meter for the first time, to save having two seperate water baths while checking my chemicals at 27C and the buffer solutions at 25C, I decided to use one bath at 27C and just drop the pH buffers by 2 degrees before carrying out the checks. What surprised me was how long it took to drop the 2 degrees!
This was 100ml of buffer solution in a 200ml beaker. Even after brisk use of the chemical stirrer and standing alone, it took up to ten minutes to drop to 25C. This leads me to believe that we may be over concerned about this particular issue and as the developing tank is sitting in the controlled water bath I would think there was little drop in temperature during the 7-7½ minutes First Developing time. Likewise I would think any drop in temperature in the centre of the tank light-trap would soon be absorbed while using inversion agitation!.
However it`s a point worth considering, though it needs a far more scientific experiment by someone qualified, to show the real facts. It would be interesting hearing from anyone who could carry out such an experiment, and indeed hearing from Reverend Hatful when he has carried out further tests.