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Thread: BTZS developing and light

  1. #1

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    BTZS developing and light

    What light bulb can I use with BTZS development? I realize that the tube is light tight, but when I take the film out to put in the stopper, what light source can I use safely? Fred Newman states that he never has had any issues with the viewing light on. Im just a little nervous.

    Are there lights that I can buy off the shelf?

  2. #2
    おせわに なります! Andrew O'Neill's Avatar
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    Re: BTZS developing and light

    I don't take the film out of the tubes when it's time for the stop bath. Both tubes and film are plunged into a tray containing the stop. When it's time to fix, the sheets are removed from the tubes.
    I've worked with a 60W tungsten bulb which is about 6 feet away with no problems.

  3. #3

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    Re: BTZS developing and light

    15 watt about 4 to 6 feet away. Most people just work with a normal safe light. I have tested with normal room light [60 watt] and densitometer test shows no fogging with 100 iso film. As Andrew said leave the film in the tube and plunge it straight into the stop bath.

    Fred has more experience with this than most. Phil Davis always said to get the film in the stop bath quickly and you have no issues with fogging.

  4. #4

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    Re: BTZS developing and light

    Room lights should be fine when plunging the tubes into stop bath. But it seems like bad manners so I use the safelight, i.e. a dim light, until the film is in the fixer.

    I use a slosher in a tray of fixer. I remove sheets from the tubes and fix in the slosher. It's fun to watch the film clear.

  5. #5

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    Re: BTZS developing and light

    I piped in a recent discussion of this and something interesting was brought up...

    If you are using an alkaline fix, you might want to verify that development does not continue in the fixer.

  6. #6

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    Re: BTZS developing and light

    Bill, how would you figure that out?

  7. #7

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    Re: BTZS developing and light

    My experience is with acid fix, so when I said something like "when you put film in the stop, development stops so opening the tubes can't hurt anything" I was corrected by people who use water rinses and alkaline fix.

    But if I was to design a test to prove that it is safe, I would go overboard with the light to get a measurable density.
    1. Expose 2 pieces of film to a step wedge.
    2. Develop normally.
    3. Expose one sheet to bright light immediately after developing and while immersing in stop. Probably 100 watt at four feet.
    4. Fix that one sheet in the same bright light.

    At the worst (or best) case I would expect some measurable "Sabbattier" effect. Based on the anecdotes, I'd say it would be a very close measure.

  8. #8

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    Re: BTZS developing and light

    By doing 2 step wedges exposed identically - one developed in total darkness and the other under whatever light conditions you have, then read and plot them in WinPlotter. Even with Pyro I use a half strength stopbath and have no problems with fogging.

    People are either convinced or they are not. If you actually use the tubes to do your processing you will answer the questions for yourself and I would suggest if you have any doubts run your own test.

  9. #9

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    Re: BTZS developing and light

    Quote Originally Posted by Bill Burk View Post
    My experience is with acid fix, so when I said something like "when you put film in the stop, development stops so opening the tubes can't hurt anything" I was corrected by people who use water rinses and alkaline fix.

    But if I was to design a test to prove that it is safe, I would go overboard with the light to get a measurable density.
    1. Expose 2 pieces of film to a step wedge.
    2. Develop normally.
    3. Expose one sheet to bright light immediately after developing and while immersing in stop. Probably 100 watt at four feet.
    4. Fix that one sheet in the same bright light.

    At the worst (or best) case I would expect some measurable "Sabbattier" effect. Based on the anecdotes, I'd say it would be a very close measure.
    Interesting test Bill but irrelevant to BTZS methodology unless the aim is to actually ruin film. The tubes are taken from the water bath inverted and the cap removed and with the tube still upside down and away from the light it is placed quickly into the stop bath. All up about 3 - 5 seconds.

    Over the weekend I will try a sheet with water and one with stop bath and see if there is any difference. I use a 15 watt bulb about 4 -6 feet away.

  10. #10

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    Re: BTZS developing and light

    Quote Originally Posted by Steve Nicholls View Post
    Interesting test Bill but irrelevant to BTZS methodology unless the aim is to actually ruin film. The tubes are taken from the water bath inverted and the cap removed and with the tube still upside down and away from the light it is placed quickly into the stop bath. All up about 3 - 5 seconds.

    Over the weekend I will try a sheet with water and one with stop bath and see if there is any difference. I use a 15 watt bulb about 4 -6 feet away.
    I think the "key" to this test is to use a water stop bath and an alkaline fix like Photographic Formulary's TF-4. I get the impression the alkaline fixes work a bit like a monobath, there could be some processing that occurs.

    I believe an acid stop and fix would work as always to stop development before any effect occurs.

    Even when you deliberately go for Sabattier effect, a short second development after a long main development has very little effect.

    So I am confident that given the years of experience people have had with the BTZS tubes, there probably won't be any significant difference between test and control. But it's worth quantifying given the popularity of alkaline fix.

    I don't think anyone would be inconvenienced if it turns out that 15 or 40 watt bulbs are recommended versus 60 watt.

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