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  1. #21
    Photo Engineer's Avatar
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    A pre-wet is advised to temper the drum and film to 100 F. It causes no problem and helps a lot. I have run lots of film this way for over 20 years. It works.

    Retained silver in the film causes muddy color in prints, higher grain, blocked highlights, and sometimes crossover. Retained or excess silver in the chemistry causes retained silver in the film so it causes the same problem in the end.

    Remember that you can have retained silver metal and retained silver halide depending on where the silver retention problem takes place. The retained silver halide will gradually darken causing dmin to go up and shadows to become compressed with odd color crossovers. The retained silver metal is mostly retained in dark areas in the negatives which cause the highlights to become compressed and odd color crossovers. Grain can go up at either end depending on the type of retention.

    PE

  2. #22
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    To PE you have answered the questions that were asked of me, which is good as I wouldn't have been able to answer a technical question as well as you have. I will also check out my regenerating of the bleach system and maybe upgrade it a bit.

    I do have a query though on pre-wetting film and paper. For some years I was regularly pre-wetting both films and colour paper (EP2) then one summer I started getting Cyan streaks on the prints.

    As I was at the time using Agfa chemicals I contacted them and their chemist immediately asked me if I was using a pre-wash for my prints, which I replied that I was. His next statement made me re-think about pre-wetting.

    Basically he advised that we were in late summer, the dams were quite low and as a result of that, the water authorities added a flocculant to the water to make the precipitates drop. This gave them an easier chance to engineer clearer drinking water. However this flocculant also had a side effect on unprocessed colour paper.

    The advice was to resist a pre-wet in both paper and film developing as it isn't required if the system is up to temperature. I stopped pre-wetting then and there, and haven't looked back since. I still have a piece of a print on the darkroom wall showing this cyan streaking caused by the said flocculant.

    Since then I have gone over to roller transport paper processing and it doesn't worry me about paper, but I certainly do not pre-wet my films, either B&W of colour.

    Mick.

  3. #23

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    Quote Originally Posted by Photo Engineer
    A pre-wet is advised to temper the drum and film to 100 F. It causes no problem and helps a lot. I have run lots of film this way for over 20 years. It works on the type of retention.
    PE
    PE, I temper the drum and film dry, and it's never caused me a problem. They both get up to 100F in 10 mins or so.

    I'm not questioning your expertise (you are without a doubt one of APUG's most important contributors) but have you tried without the tempering wet bath?

    Graham

  4. #24
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    To Mick and Gbroadbridge, here are some hints.

    Papers contain high chloride emulsions. As such, they are senstive to chlorine and other halides and some chemicals used in water treatment. However, the manufacturers know that and engineer their papers (or should) to avoid that very problem. I have never observed that problem with any variant of Kodak papers. I have never heard of it with Fuji papers. Agfa papers have been such a small runner that I am not familiar with their response.

    I use a pre-wet all the time.

    Early instructions from Kodak and Jobo among others recommended a prewet. I have found that I get uniformity problems in both paper and film without one, and sometimes get variable results along with air bells due to bubbles. So, I find it a plus.

    Now, as for cyan streaks. I have found that the most usual cause of cyan streaks is due to insufficient stop action after developing RA paper, particularly at high temperatures. If I use a stop, I never get the streaks, but if I omit it, I get streaks. This is due to fixation and development taking place side-by-side at the same time in that hot drum.

    Here is my process:

    Prewet 100 F 45"
    Develop RA-RT Repl 45" - 1' Depending
    Stop 30"
    Blix 1'30"
    Wash 2'
    Dry

    My C41 process is the EK process with two 30" 100F prewet stages.

    Thank you for the nice comment. I try to help here as much as possible drawing on my experience in product and emulsion development work at EK.

    My warmest regards to everyone who has shown an interest in this. Please feel free to contact me personally with questions. Some people seem to feel reluctant. I really don't mind at all. I keep busy on these cold rainy (soon to be very snowy) Rochester days answering mail and chatting or working in the DR.

    PE

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