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  1. #71
    Ian Grant's Avatar
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    Theory also breaks down slightly because hard water washes films & papers more effectively than soft water (or de-ionised/distilled water).

    Quote Originally Posted by Photo Engineer View Post
    This is why a practical result is always so much better than the math model.

    PE
    So that's another reason why Ron's comments are important here.

    Ian

  2. #72
    Photo Engineer's Avatar
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    Ian;

    I would like to add:

    Depending on the ions, some hard waters can slow down washing. This is due to the decrease in swell caused by Sulfates, and the change in swell due to the pH of some water supplies. For example, water with a lot of Calcium Sulfate or Aluminum Sulfate, which would be slightly acidic (beyond the norm introduced by Carbonate perhaps), would sharply decrease swell.

    In addition, Calcium ions tend to slow fixing and washing due to the nature of their effects on hypo.

    This is why I suggest running tests with your local water supply, as it can have a major impact on the final times of fix and wash.

    PE

  3. #73

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    Quote Originally Posted by Diapositivo View Post
    I don't understand a lot of this from the theoretical point of view, but the lesson I get from this is:

    If 0.01 g/sqm residue is "commercially" sufficient, than Greg tests give peace of mind to all those who follow this procedure, provided the water is not significantly different;

    To take into account difference in water quality, add another rinse. No problem.

    Because 0.01 g/sqm might not be enough for archival quality, add yet another rinse and you'll have archival quality anyway, so that your grand-grand-nephew can make observations about your pictures, after having already inherited from your heirs that is.

    So any published method for washing is good for most purposes (thanks Greg) and if you really want to be sure to reach archival quality just add a rinse or a couple of rinses (thanks Erik) for your descendants' enjoyment.

    Fabrizio
    Water is cheap.
    You relly did grasp this Fabrizio!

    I have nothing further to add,my post was NOT an attack an Greg, nor on PE, it was just to highlight that the testing method will measure down to COMMERCIALLY sufficient levels, beyond that it simply says nothing meaningful.

    I can live with that. because I always washed to archival levels anyway, not because I'm overly concerned with that, but because water is cheap where I live, and because I can.

    I used to use running tap water, but think that is a nuisance around HERE, this being Norway, we have very cold tap water (no ice needed when I enjoy my oirsih whiskey!!).

    Since I'm more concerned with emulsion reticulation than remaining thiosulphates, I decided to go to slush-and-discard watering, I can conntrol water temperature within 1 degree Celcius that way.

    I did a little research, dug out long forgotten school training, my chemistry class, I'm an old chemical engineer. So I discovered that this watering business was in line with my classical formal chemistry education, and EUREKA, the good old Ilford system was better from bolth a teoretical and practical point of view. For ME.

    You can do what you like, as long as the film spend enough time in water and you use enough of it or changes it enough, you will be good. You will reach commercial levels easily and fast, archival levels with just a little more work or time.

    This is really no big deal, its almost infathomable that anyone can spend so much time debating such a simple issue,m and make something so simple look so hard.

    Have a nice time all of you, but make damn sure you spend a lot more time photograping, than debating issues that was debated to death more than a century ago.

    Erik

  4. #74
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    Out of Curiosity. When I worked with Microfilm, We were always to ask for a "Methylene Blue" test that said the film was washed "sufficiently". I only saw a consultant once with a bunch of dropper bottles and a penchant for only working when he was alone.

    What is the difference between the MB test and the Silver Nitrate test that we are discussing here. Would sending some of the Doubters off to repeat this test sequence with Methylene Blue help the cause?
    Charles MacDonald
    aa508@ncf.ca
    I still live just beyond the fringe in Stittsville

  5. #75

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    "There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).

    Regards
    Bill

  6. #76

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  7. #77
    Photo Engineer's Avatar
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    You see why this method is not just for anyone? Also, there are standards, as I have stated before, for retained HQ and Metol, but there is no good test for them either.

    PE

  8. #78
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    Anyone interested in my test setup, here are a couple of images. One is of my flow meter and homemade stand. The plug on top is there until my screw in thermometer arrives later this week. The other picture is of the test to determine the necessary flow rate by adding food coloring to the water in the tank, and I only had green available. The thing entering the tank is a stainless steel tube small enough to go through the core of a Hewes reel. By adding a rubber stopper on the end, I can plug up a plastic tank for forced washing, as well.
    Attached Thumbnails Attached Thumbnails DSC04001.jpg   DSC04240.jpg  
    www.gregorytdavis.com

    Did millions of people suddenly disappear? This may have an answer.

    "No one knows that day or hour, not even the angels in heaven, nor the Son, but only the Father." -Matthew 24:36

  9. #79
    Photo Engineer's Avatar
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    Very nice Greg. Well done.

    PE

  10. #80

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    Quote Originally Posted by cowanw View Post
    Pretty mundane stuff for anyone trained and with experience working in a modern lab.

    In my day we did this manually of course, measuring with precipitates and such. You would spend a *lot* longer analysing anything than just washing a little longer.....

    And that link to a 124$ or was it £, for a PDF-file describing the process was hillarious, some are prepared to being shafted or to quote JP Barnum *there's one sucker born every minute*!!

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