MINI - DEVELOPING TANK
BOB SWIFT Area 20
Having to develop a short length of film to print some urgently required passport photos and foreseeing the use for developing contrast masks for my Cibachromes, I decided to construct a developing tank that would use a minimum of chemicals for the four or so frames required.
The construction is well within the scope of anyone, being made of easily available components.
MATERIALS REQUIRED:- The main body; I used an Ilford XP1 drum that I bought 30 metres of film in, but a chemist`s plastic medicine/pill box is as good, perhaps better. The filter neck and cap are a black 35mm cassette container. The central part is again a medicine container as large as possible but leaving one/eighth to three/sixteenths of an inch gap for the film.
CONSTRUCTION:- Cut a hole in the lid of the main body about the size of the small end of the cassette tub using a sharp knife or similar. Wrap a small piece of "wet or dry" or Emery paper around the tub and twist it around in the lid hole. This will give a smooth round hole which will seal well, but don`t make it too big. To align the tub in the lid in the proper place whilst the glue sets and to give a more robust construction, a groove is required around th tub. This is very easy to do. Place a hacksaw blade on top of a block of wood, overlapping the edge by about one/third of the tub`s thickness. Hold these down by hand or clamp them down then rub the tub along the blade until you have a groove all round. You will probably find that the groove is too narrow, put a piece of card or similar under the blade and repeat the operation. Push the tub part way into the lid, it should be a tight fit as the tub is tapered, run some glue around the groove and push the tub in until the groove locates. When the glue has set cut off the bottom of the tub leaving a slight ridge.
The tank base is made the same way; cutting a hole, rubbing it smooth, inserting the central tub with groove, but leaving it whole. This can be filled with warm water to help stabilise the developing temperature, position the groove to make a gap of no more than one/eighth of an inch, between the inner part and the filler neck.
To prevent light en
tering the tank when the filler cap is off I glued the black piece cut out of the main body onto the light grey inner tube and rubbing it with emery paper to remove the gloss finish. I also black Humbrol Modelling enamel (camera touch-up paint) to the inner part (none-solution side) to prevent light coming through the grey plastic.
My tank takes about 35cc of solution to develop four frames of 35mm film and I`ve used it for monochrome, C41 and E6 and it hasn`t melted, dissolved or effected the chemicals. The drawbacks I`ve found are the Ilford tank leaks slightly if not tightened up enough, but overtightening makes the lid jump the thread. An elastic band outside as a thin gasket inside would cure would cure this fault but perhaps a chemist`s tub with a press on top would be better. Also the film tries to wrap around the inner part but using a swirling rather than inversion agitation gets the solution to the emulsion.