Hi Richard
Thank you very much for your considered response. My apologies for the delay in replying - I was caught up in the throes of designing a solution.
To clarify, when i say I cannot guarantee a clean environment, i was referring to the area outside my sterile corridor into which I would have been pulling film from the slitter. My preference is for a limited area which i can try to guarantee is dust free. I am considering blowing filtered air through it to create a positive pressure chamber. Ideally, I would like to be able to transport the rig to any darkroom and get to work with relative ease.
I didn't really understand your reference to a shorter film guide - would you mind explaining?
My proposed system minimises film handling. I plan to have the original film reel on a system that can travel the length of the corridor. I will move the reel to one end then clamp the film at the start position and then spool film off the reel as I move the reel back. Once I am sure I have arrived at the other end a 'safe' guillotine will be used to slice the film after it has been clamped. Once the film has been laid down, the reel is moved further down the track and out of the way.
The slitter is then run along the corridor. I am, at the moment, planning to slit from both sides, which will result in a partially perforated border and i do worry about the possibility of the film snarling up when i try to insert it on to development reels.
At each end a prepared piece of backing paper is slid under the film and taped to the film (the necessary precautions will be taken to ensure that the film is centred on the backing paper and that the area of backing paper under the film is correct and consistently the same.
The film is then wound onto a spool using a manual crank. Ideally I would do this just once getting the tensioning right by weighting the whole spool at one end but if i need to i might have to spool it the wrong way round and then put it in a camera or a back that allows winding of the film (I'm assuming mamiya 220 backs allow this without being attached to the camera).
Issues:
1. Cost - i'm not a diy person so this will have to be made for me. If it is too expensive, the project will die.
2. Dust - As I say above, if i need to i will make a tent over the sterile corridor.
3. Film curl when laying down the film from the reel. The plan is to do the whole thing without touching the film except possibly for a very small area at either end - if the film is threatening to curl away, this might make it difficult.
4. Ensuring that the corridor is smooth and does not damage or cause the spool to catch. I'm considering lining the corridor in a soft fleece like material but I must also avoid the risk of generating static electricity which would attract dust particles - (of which there should be none, hmmm)
5. Backing paper - I understand that commercial grade backing paper can be purchased from Ilford via their annual ULF program but I also hear that it is quite costly so I am interested in possible alternatives. I was given to believe that there really weren't any that meet the stringent requirements of effectively shutting out light and not reacting to the film. But you mention that you have used an alternative in the past. What was your experience with it and would you mind sharing its source? I am thinking that since the emulsion is only briefly in contact with the backing paper (including when wound on the spool), the stringent requirements might be more easily met with 220 film.
Thank you for the clarity of what you have written on this thread - it played a big part in convincing me that this is doable.
mainoo
