During development, the film is continuously wound back and forth between two reels along its entire length. The reverse exposure is carried out through a small, sealable window through which the film passes. Meanwhile, a powerful lamp is positioned in front of it from the outside.
That’s a bit awkward.
Is the sentence perhaps intended for chemical reversal and simply mislabelled?
No, certainly not.
You wrote that every part of the film must be exposed to light for 30 (!) seconds.
Correct. Actually a little longer, depending on the lamp’s intensity.
If you left the film in the tank, you’d first have to turn the crank slowly for about 2 hours until this condition was met. How is that supposed to work in practice?
It wouldn’t work at all, which is why this type of tank is rather unsuitable for reversal development. A possible workaround might be to open it up, fill it with water and shine a powerful halogen lamp on it whilst you turn the handle veeeery sloooowly.
With other tanks, you simply take the reels out and perform exposure for several minutes.
Just as confusing is the issue with the Bleach bath: your colleague, Ms Winkler, mentioned in a second email that the Bleach bath was probably not prepared correctly (dark grey-brown discolouration). She also mentioned that the Bleach bath would ‘go off’ within 10 minutes anyway. Incidentally, that wasn’t in the instructions either; it merely stated that prepared solutions would only keep for a ‘short’ time, whatever one understands by ‘short’.
If the Bleach bath is already brown, it’s completely ruined. Even if it’s still a deep purple, it might already be past its best.
Prepare, filter, use.
The stuff oxidises away incredibly quickly. Also, if you notice a lot of brown residue forming whilst filtering, you should prepare the Bleach bath with deionised water.
Accordingly, I prepared the bath about 20–25 minutes before use and had to stir for quite a while until the potassium permanganate had dissolved completely.
The stuff rarely dissolves completely; moreover, contaminants in the water cause brownstone to form, which you simply can’t dissolve, so: -> Filter!
And don’t stir excessively, as this just introduces too much oxygen into the solution and the stuff goes off even faster. Water, acid, permanganate. Close the bottle and tilt it slowly three times (do not shake) – that’s enough.
Last but not least: how can you prevent the Bleach bath from tipping over prematurely, given that the film’s processing time is already 8 minutes?
You can’t. The bleaching time is generous, and once the stuff comes out of the tin, it’s done. Completely.
In any case, the final result is that the negative images have not been separated and no reversal has taken place. Also, the silver fog in the normally clear areas (of the negative!) has high density and lets very little light through. This fog is also particularly easy to spot when looking at the film from the emulsion side. It has a distinct dark grey-brown colour.
All of this suggests that – in addition to the problem with the ‘dead’ Bleach bath – the film wasn’t fixed sufficiently. Extend the fixing time.
Does anyone here have experience with a daylight tank like mine?
I don’t think much of them. It’s bloody hard to stick to the times (insofar as the times specified for tilt-and-turn or rotation development are even usable), as contact with the chemicals is very brief, you crank it faster or slower depending on your mood, and the second exposure is a nightmare anyway, but you’ve noticed that yourself :) .
Perhaps you should try using a different tank. Lomo makes a tank for 16mm film that works similarly to the well-known Jobo canisters, meaning the film is wound onto a spiral (transparent, ideal for double exposure). However, it only just fits 12 metres in one go.
