Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 68,678   Posts: 1,482,125   Online: 975
      
Page 2 of 2 FirstFirst 12
Results 11 to 15 of 15
  1. #11
    benjiboy's Avatar
    Join Date
    Apr 2005
    Location
    U.K.
    Shooter
    Multi Format
    Posts
    6,408
    Have you tried the experiment with a scrap film in the tank, because the surface area of the film can have an effect on the temperature drop, and if you're doing a dummy run all the factors should be the same.
    Ben

  2. #12
    Rudeofus's Avatar
    Join Date
    Aug 2009
    Shooter
    Medium Format
    Posts
    1,424
    Images
    10
    Quote Originally Posted by benjiboy View Post
    Have you tried the experiment with a scrap film in the tank, because the surface area of the film can have an effect on the temperature drop, and if you're doing a dummy run all the factors should be the same.
    The fact that I ran my experiment with an open lid will distort the results a whole lot more than whether there is film inside the tank or not - and frankly I don't see any reason why surface area inside the tank should affect the temperature profile at all.

    A lot of folks here posted comments about rotary processing, but this is a completely different animal as the quantity of soup is much lower. Of course such a setup will have a much more pronounced temperature drop over time, that's why good rotary processors have a water bath. My experiment provided good evidence that inversion tank processing maintains the temperature inside the tank quite well.

    Personally I don't think that putting an inversion tank in some uncontrolled water bath is such a good idea: the temperature drop in that water bath will be much worse than the temperature drop in the tank itself without the water bath.
    Trying to be the best of whatever I am, even if what I am is no good.

  3. #13
    Diapositivo's Avatar
    Join Date
    Nov 2009
    Location
    Rome, Italy
    Shooter
    35mm
    Posts
    1,844
    Quote Originally Posted by Rudeofus View Post
    Personally I don't think that putting an inversion tank in some uncontrolled water bath is such a good idea: the temperature drop in that water bath will be much worse than the temperature drop in the tank itself without the water bath.
    I might be wrong (never been a champion in Physics) but if you fill a plastic basin with warm water (warmer than needed so that a certain heat is used to warm the container itself) shouldn't the higher thermal mass of the water surrounding the tank require a larger "contact" with the room air in order to be chilled, than the air itself?

    In more understandable terms:
    If the tank is surrounded by air, air and tank will exchange heat, air will get warmer, tank will get cooler. This exchange is influenced by several factors (surface, temperature difference, "wind") and by the "thermal mass" of both air and tank.

    If the tank is immersed in water, and water is contained in the plastic basin, and the plastic basin is immersed in air the heat exchange will take place between the basin and air, and between the water surface and air.
    But considering that the plastic basin, and water, have a considerably higher "thermal mass" than air, you will need "much more air" to cool down the higher thermal mass. That's why I expect the plastic basin with warm water to cool down more slowly than the tank when exposed to air.

    In a word: you can use water as a accumulator of temperature that will discharge more slowly than air, when in contact with air. It will also "insulate" the tank from the cooler ambient air, a bit of a "thermal mass overcoat" for the tank.

    (Not that I am sure of this. I am just reasoning).

    Fabrizio
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

  4. #14
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,708
    Images
    65
    You have forgotten evaporative cooling. The larger the surface area of the hot container (bath) and / or the lower the humidity, the faster the hot bath will cool down! Another law of physics. Sorry.

    Without constant renewal of heat, you are bound to cool off.

    Kodak suggests starting a degree warm and finishing a degree low so that over the development time, you get an average "good" temperature. So, start and 101, and end at 99 in 3' 15" for C41.

    PE

    PE

  5. #15

    Join Date
    Aug 2006
    Shooter
    Multi Format
    Posts
    56
    Thanks for comments. I will redo the experiment with the water bath filled as full as it can be filled.
    I have had inconsistent results with C41, with the same films developed in different runs needing different filtrations when enlarging. Some runs have been OK, but none have been as good as the negatives I get from a commercial lab. Those have better contrast and higher density than any film I developed myself and I can use the same filtration for each and every film (of the same type) when enlarging. The film base color is always lighter in the negatives I have developed myself than that of those developed in a commercial lab.

Page 2 of 2 FirstFirst 12


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin