Stuart Tallack has sent me the following comments on using the Optochrom tank:
I realise that I am likely to be the only one using an Optochrom but, just in case, I have a few additional notes. A friend asked if she could try the Optochrom with an old scrap film with a view to borrowing it from me in the future. She made a few suggestions which I pass on.
First. I foolishly wrote that you should pull out the backing paper until the highest number appear! I meant the lowest number.
Second. My guinea pig’s version is as follows. (She is right handed.)
It is very easy to drop bits of the tank so work on a table or bench and give yourself plenty of room. To insert the film, separate the two halves of the spiral. Hold bottom in left hand and remove the spigots. Place them near to their ‘homes.’ The larger one goes on the right; that is to say, the top of the tank when re-assembled. Put the film reel in and replace the spigots. Now take out the seal and seal retainer and place safely away from edge of the bench. Put back the top half of the spiral (which includes lid and funnel, of course,) on to the bottom spiral.
Pull out about three inches of the backing paper. With tank in left hand and spiral in right, put the latter carefully into the tank so that the backing paper slips into the slot in the tank. Put a stout elastic band around the tank and lid… a stout one, not the one the postman dropped on the path! Pull out the backing paper evenly and straight until the lowest number appears and there is resistance to pulling. Cut off the backing paper near to the slot. You can get a small pair of scissors right in to cut it close to the slot. Put back the seal and seal retainer. At this point, the film should be neatly wound on to the spiral. If it isn’t, you will not know until you have finished development, but that is true of any daylight loading tank!
That is it. She filled in some gaps. I would add that Kodak and Ilford films are fine but thicker films are reluctant to enter the spiral. If thinner films give trouble, try altering the angle of the guide blade by careful bending. I have not needed to do that.