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Thread: Stop baths

  1. #31

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    Quote Originally Posted by gr82bart View Post
    So what's the professional / really experienced recommendation - stop bath solution or water? Assuming plain Jane developer like D-76.

    Regards, Art.
    Well, as far as the "professional" part of the question, the newspaper where I worked (pre-digital days) never used a stop bath with film. We just dunked the film in a tank of running water and tossed it in the fixer tank (in the dark, of course). We didn't have to buy the fixer and didn't really care if the fixer was exhausted or not--just as long as we could get the film printed ASAP for the editors to see.

    As to personal recommendations, I use a stop bath because I have to buy my own fixer, I want to get the most out of it and would prefer my negatives to last for a while.

    For prints? The newspaper used a solution of glacial acetic acid mixed fresh daily. I use the same type of indicator stop bath I use for film and mix fresh when it starts to change color.

  2. #32

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    Stop stops development, water baths only slow it. Decide which approach will be acceptable for you.

  3. #33
    JBrunner's Avatar
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    I use water for film and paper. For paper I use a two bath process, so very little developer carries through to the fixer.

  4. #34

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    I'm always amazed at these discussions. The one thing that never seems to come up is what is the pH of your water to begin with. In most of the temperate regions of the US (and I assume the world) the pH of tap water will be slightly acidic to neutral (pH 6-7). Here is the desert SW, the water for the City of Albuquerque has a pH of 8, on the alkaline side. Using a water stop with an alkaline developer will just slow down the developer, not stop it quickly like it is supposed to.

    Personally, I usually use a half strength mix of Kodak indicator stop. For certain developers, Diafine and DiXactol, I use water.

  5. #35

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    Quote Originally Posted by r-brian View Post
    The one thing that never seems to come up is what is the pH of your water to begin with.
    Perhaps because the pH of the water is rather trivial, especially compared to the acidity of an acid stop bath. And when I use the term "acidity", I'm referring to the amount of acidity that is available in the stop bath to neutralize the base in developer.

    Whether your tap water is pH 6 of pH 8, it may have very little buffering capacity and have a negilgible effect on the neutralization on the developer other than merely diluting it. Of course, a pH 8 water can't "neutralize" the developer as it has no acidity.

    Bill Troop recommends using a buffered stop bath for a high efficiency stop. It consists of acetic acid and sodium acetate combined to make a buffered solution which has moderate pH that is around 5, but it has a very large amount of acidity with which to rapidly neutralize the pH of the developer and stop development very quickly.

  6. #36
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    About 17 years ago, I started using a stop bath after first developer in the C41 process. I was informed by quite a few people that using just water would be more than alright, I was being fussy they said.

    At the time, I was processing quite a lot of Kodak Print film, which was designed for turning a colour negative into a transparency (slide). As absolute accuracy is required to get a colour corrected transparency from the colour negative, it means that your processing has to be spot on and/or, always the same.

    One of the advantages I had, was that I worked in an industrial photo lab. Deciding to check out empirically whether a plain tap water bath would arrest developing in all the layers, I ran C41 control strips, which had been carefully kept on dry ice. Then it was a simple matter of getting the lab technician to run these control strips through the measuring equipment, to ascertain how close to perfect they were.

    If I used a stop bath, (acetic acid) then my control strips were right on the money. If I used a water bath as a stop bath, then the control strips were ever so slightly off. It was either the bottom or top layer that was slightly off, I cannot remember.

    I have used a stop bath ever since, on all hand developing processes, B&W and colour, film or paper.

    Mick.

  7. #37

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    Quote Originally Posted by r-brian View Post
    Using a water stop with an alkaline developer will just slow
    down the developer, not stop it quickly like it is supposed to.
    I don't think a stop is "supposed to" stop quickly. It's just
    that an acid stop DOES stop quickly.

    I'm of the opinion that a water stop is as quick as an acid stop.
    Two reasons: stop is 98% H2O. H2O compared with acetic acid
    is a swift far traveling molecule. Dilution is quick. Second: H2O
    is near neutral and so as it quickly enters the emulsion it
    stops developer action.

    The main reason for an acid stop is to maintain the acidity
    of an acid fixer. Dan

  8. #38
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    A water rinse with color will slow down development based on diffusion with the top layer slowing first, the next layer and etc until the bottom layer is reached. Therefore there will be a color shift. It will be on the blue-red axis usually or yellow-cyan depending on the film and process.

    Water is not the determining factor in using a rinse after development. Water diffuses inwards at a given rate, and the developer chemistry begins moving outward slowly. Carbonate and Borate are huge molecules and diffuse slowly and HQ and Metol are also large. So, incoming water is rapidly lowered in pH by the slow moving alkalis, and the slow moving developing agents may then continue to react as pH continues to be high and then slowly drops.

    OTOH, a hydrogen ion, present in abundance in an acidic solution will reach the bottom of the film or paper faster than any other ion. This movement is virtually instantaneous. It can take 15" to 30" for the other chemicals to diffuse that distance.

    An easy way to check this out is to dip a piece of fogged unprocessed film into developer. Watch the BACK of the film and look for the back to begin development. Compare that time to the same change on the FRONT of the film under the same conditions. That is how long it takes for development to start (and stop). This is rough, but will show you the effect in most cases.

    PE

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