dkwrt200
Does anyone know of any issues with electrostatic discharge – or better still: does anyone know of a solution to electrostatic discharge? I’d only ever seen this sort of thing in textbooks before. A few nice flashes on the negative; strangely enough, not across the whole roll of film, but only on individual frames. The film was a Foma 100, loaded into an old Rada roll film cassette on an equally old Linhof. Could the film have built up a charge during transport? Apart from the viewing window and the reel, the cassette is made entirely of metal. Or was it when rewinding it into the canister (Rondinax 60 made of Bakelite)? When removing the adhesive, I took my time, as one should. Do I now always have to use an earth cable when taking photos and developing, or does this simply happen once in every 100 films?
Best regards,
Rainer
Gast
Higher humidity can sometimes work wonders.
A grounding strap, on the other hand, doesn’t help at all.
Electrostatic discharges are an attempt by two differently charged objects to equalise their potential. Whether one of them is earthed or not has no effect whatsoever on the potential of the other object; a discharge will take place regardless.
To prevent discharges, you need to avoid potential differences. This is achieved when all objects involved are at the same potential – in the case of your film cassette, you must therefore ensure that the film has the same potential as the rest of the metal cassette.
This can be achieved by connecting the film to the casing via a conductive object.
A simple metal edge will work, but the film won’t look very nice afterwards. One option would be one of those carbon fibre brushes that used to be used with record players...
Under what indoor conditions do these problems occur for you? Perhaps increased humidity is enough (turn the bathroom into a darkroom)...
dkwrt200
Thank you very much! It’s unlikely to have been down to a lack of humidity; it was snowing when I took the photos, and the darkroom is in the bathroom. Could it be because, when opening and closing the shutter, the metal rubs against the (velvet) seal, causing a bit of air to be let in and then out? That would explain why the flashes only appear on some of the photos. Would it help to simply open and close the shutter a bit more gently? Besides, the problem doesn’t occur all the time. The films I’ve used so far have all been fine (even in very dry weather).
Best regards,
Rainer
