Stuart Tallack has followed up his comments on the Optochrom Automat (for 120/620 film) which he bought off eBay (26 March 2014). My original posts on the Optochrom were on 5 November 2013, 15 December 2013 and 24 December 2013.

“I will probably remain the only person using an Optochrom tank, but just in case anyone else wants to try, here are some details:

Using the Optochrom Daylight Loading and Developing Tank

Please read Note 3 before you do anything. After these instructions, I have added a description of the tank which will make sense if you refer to the drawing from the German patent.

Remove the seal and seal retainer from the tank. If the tank is disassembled, slip the upper spiral (complete with lid and filler funnel) into the tubular extension of the lower spiral. Hold the lid on so that the corner nearest the m of Optochrom is above the film spool recess. Turn the filler funnel until the dots on the spirals meet. When that happens, you will feel the upper spiral drop slightly into place. Turn the filler funnel again until the dot on it is opposite the number 1 moulded into the lid. The upper and lower spirals are now locked together. The lid can be held in place by the fingers of one hand to stop it rotating while the other inserts the film.

The film spool has to drop straight into its recess without tilting, otherwise the ends of the spool will not clear the metal blade which guides the film towards the spiral. For that reason, the two little spigots must be unscrewed, the film on its spool pushed in under the spring knife and the spigots replaced.

Pull out 3” of the backing paper and put the whole spiral assembly into the tank so that the pulled-out backing paper is in the slot in the side of the tank. Ensure that the lid is fully on.

Pull out the backing paper slowly and gently and quite straight. (Very slowly until the highest number appears.) There is a possibility of the corners of the leading edge of some films snagging as they enter the spirals. Gently moving the backing paper up and down may help. When the number 1 appears, and resistance is felt, tear off the backing paper as close to the slit as possible. Best to use two hands for this. I found it easier to snip with a small pair of scissors, then with the tip of the scissors to push back the end of the backing paper which is attached to the film.

Holding the tank so that it is on its side, replace the seal and the retaining bar tightening the two bakelite topped screws finger tight without straining them. (On its side merely to avoid dropping anything!)

Pour in developer. I have no instructions so do not know how much was originally advised. I am using 400 ml at present. Tap several times to dislodge bubbles. The patent states that the spiral can be moved back and forth a little to dislodge bubbles and that there is a very limited vertical movement possible for the same purpose. This freedom to move is intentional and is mentioned in the Patent specification.

I have no information on agitation beyond advice in a supplement to the original instructions (which I have not got) against up and down agitation. You certainly cannot invert the tank. The Supplementary Instruction also advises, “It is important at the start of and during development to grasp the tank firmly with both hands, close the aperture in the filling funnel with the thumb and shake up the developer lightly.“ You can, of course, place your thumb over the hole in the funnel and agitate by shaking sideways, sliding or rotating the tank in circles. Follow developer instructions re timing.

Remove drain plug to let out developer.

Stop bath, fixer and rinsing are up to you. If you are happy with tap water for rinsing, leave out the drain plug and put a hose on to the top. If you prefer temperature controlled water from a jug, you can put your finger over the drain hole while filling and remove finger for draining. If you do close the drain hole with your finger, be careful how you hold the tank. Once full of water, it is fairly heavy; if you drop it, it will break! A final wash with Photoflo and you are done. Before taking the spiral out of the tank, remove the seal and the retaining bar to release what remains of the backing paper.

1. The total volume of the empty tank is about 650ml. The displacement volume of spiral and film spool holder, in fact everything beneath the lid, is about 185 ml. Filling to half an inch below the lid should cover the spiral and takes about 95cc less. 400 cc therefore seems a safe starting point. It is probably too much.
2. Ilford and Fomapan seem to feed into the spiral without difficulty. Thicker films catch their corners and are reluctant to enter the spiral. I think that is true of other tanks.
3. The filter funnel has a male thread at its lower end which is screwed into a corresponding female thread in the upper spiral. I believe that an adhesive may have been used on the threads. If the two parts unscrew easily, then by all means separate them, but if they do not readily part, make no attempt to unscrew them. I have seen one tank with both parts broken. You lose nothing by leaving them attached.

Description of the tank

Refer to the drawing from the German patent which is reproduced on the website [24 December 2013 but also shown below]
The tank consists of the housing 1, which is closed at the top by the cover or lid 2. The filler funnel 3 passes through the lid and developer is poured through it into the tank. The funnel is furnished with a male thread at its lower end which is screwed into a corresponding female thread in the upper spiral. (I believe that the threads are permanently joined by an adhesive. If anyone finds that to be incorrect, I would be grateful for the information. Pending that correction, do not try to unscrew the filler funnel.)

The lower spiral incorporates, as part of its moulding, the lower portion of the film spool recess and to it the top of the recess is attached by two screws. The ‘blade’ which guides the film on to the spiral is trapped in position between the two parts. In the centre of the lower spiral the moulding is extended upwards as a tube. The upper spiral is extended downwards as a tube connected to the filler. The two tubes form a light trap for the filler. A light trapped air hole is provided in the lid where it is largely hidden beneath the filler funnel.

The upper spiral 5 is provided with openings 8 so that air bubbles can pass through. The lower spiral 12 has apertures 6 through which liquid can move to and from the bottom of the tank. Feet 14 are formed on the bottom of 12 such that a space is left between it and the base of the tank.

To develop a film, the hose fitting is first unscrewed from the filling funnel 3, the lid is removed complete with the filler funnel and the upper spiral, the lower spiral is removed and and the sealing strips 27 and 28 are pulled out. The upper spiral is dropped on to the lower such that the dot 25 abuts against the similarly marked stop 26. Turning the filler funnel anti clockwise locks the upper and lower spirals together. The film spool with its exposed film is inserted into the chamber 16 (I had to remove both spigots to do this as otherwise the ends of the spool foul the ‘knife’) and the end of the protective paper strip is transferred into the top of the vertical slot 18 when the lid is replaced. With the lid on, the white dot on the filler funnel should be opposite the moulded number 1 on the lid. The paper backing strip can be pulled out and the film then passes through the narrow slot 21 and rolls up, with its top and bottom in the spiral grooves of the upper and lower spirals 5 and 12.

If the film catches when furling it on to the spiral, moving the backing paper gently up and down may help. After the film has been completely rolled into the spirals, the sealing strip and its retainer are put into their recess and developer then poured into the filler. During development, small rotational movements can be made on the upper spiral body by means of the funnel, and a little up and down movement (h) can be made. In this way, air bubbles can be dislodged thus avoiding marks on the developed film. (The rotational movements need to be small. Slapping the flat side of the tank would also seem a good idea to shift bubbles.)

The tank seems to be fairly robust, but the sides of the lid are very thin and likely to break or crack if dropped. Fortunately, the lid is not too difficult to repair as an adhesive such as Araldite can be built up to a thicker section where the lid has cracked. If one of the tubes attached to the two halves of the spiral is broken, a section could be turned up from black Tufnol and glued in”.

Here is a link to the original patent

And here is the digram from the patent:

Screen Shot 2013-12-24 at 10.52.23