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Discussion in 'Darkroom Equipment' started by stradibarrius, Mar 1, 2010.
At what point does the film become light safe? After the stop?
In theory, yes. In practice, it depends on how completely you have stopped it.
Even though the film can be viewed for a short time after the stop, the image will degrade in light until it is fully fixed.
You really should not view the film until it has cleared. You can test clearing time by placing a small piece into the fix and timing how long it takes to become clear. It is not fixed at that time, it is only 1/2 fixed or 1/3 fixed depending on fix, but it is no longer light sensitive under subdued light.
Before that point, even in the stop, film is sensitive to light and can change slightly.
Which brings up a question I have been meaning to ask for a while:
Are fixing and clearing two different processes? (from your reply I see they are).
Can you tell me what is happening apart from the clearing?
Clearing turns Silver halide into Silver-hypo complexes but these are still in the film and still may brown or darken. Fixing is the removal of these from the film by outward diffusion into the fix solution. However, these terms are very loose. They are imprecise and there is no clear description in human language other than a series of chemical equations. Up to 5 or 6 types of complexes are forming in Sodium Thiosulfate and more form in Ammonium Thiosulfate. These complexes are "clear" compared to the Silver halides which are milky or cloudy.
I've been using a water as a stop bath for my film these days 'cos I run out of stop bath and was in a fix (I should do stand up comedy) to get a roll processed....does a water stop bath require more fixing time than say the stop bath Kodak sells?????.....
hang on, you're Ron Mowrey who was on Inside Analog Photo Radio in that interview right???.....chapeau...you're a legend....
I'm an ordinary guy. But, I have spent my entire life in the photo industry either on the photofinishing side, the commercial side or designing photo products at EK or now privately. Just fun!
But, to answer your question, a stop should always be used for prints, especially FB, and is quite useful for film as well. It does help protect and extend the life of all fixers, even alkaline fixers. A stop can be used with TF-4, as it is so well buffered.
I won't risk my precious (i mean, precious to me) film. Just a few more minutes' waiting wont hurt
After clearing. Should take under a minute in fresh fixer. Save your trimmed 35mm film leaders for testing clearing time prior to processing
I recon that many of us have made all the mistakes ever possible and sometimes we've been lucky too. But a bit of light on the film once the development time is at its end doesn't make any difference. This makes life easier if you're not using e.g. Paterson tanks where it's easy and fast to drain and refill the fluids.
I thought that I was lucky and got away with it, but after reading the instructions for the BTZS tubes, I realized that the film isn't very sensitive to light once the development is done. As there are quite many users of the BTZS tubes and probably millions of films have been processed with those tubes, I recon that it's safe to say that the film can take some daylight at the stop and fixing stages.
I use Jobo drums with a CPP2 nowadays, but when I was using a CombiPlan for 4x5" sheets, it was a relief to just lift the lid to flush the used developer out and the stop into the tank within say 15 seconds instead of over a minute with the "prescribed" drain and fill cycle for the CombiPlan. Actually after a while I just took off the lid, flushed the used developer and poured in the stop without putting the lid back. A few "lift and drop" agitations and it was time to replace the stop with fixer. This was all done in a very soft light, a 15W indirect light on the other side of the room behind my back. Not much light, but still comfortable to work in.
I understand a certain green safelight is "safe" for a brief period after film development is half complete and would suppose something similar happens with your unsafe procedure. Those of us who learned "down and dirty" darkroom--rushed deadlines, portable darkrooms in hotels on a shoot, etc, etc. would turn on the lights after the film had been in the fix for a short time--but never before.
You may be very lucky; or everything I thought I knew (and which was taught me by cigar-chomping old pros, some of whom went back to the glass plate era) during the last fifty years or so is wrong.