Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,542   Posts: 1,544,402   Online: 1022
      
Page 1 of 8 1234567 ... LastLast
Results 1 to 10 of 71

Thread: Chemistry

  1. #1
    Ed Sukach's Avatar
    Join Date
    Nov 2002
    Location
    Ipswich, Massachusetts, USA
    Shooter
    Medium Format
    Posts
    4,520
    Images
    26
    In using both C-41 and RA-4 chemistry, there is a definite shelf life, which can be extended - a lot - by displacing the oxygen in partially filed containers with an inert gas.

    JOBO / Tetenal catalogs a product called "Protectran" for this purpose. In trying to get this (comes in a spray can - I have *one* left), I was just informed that it has been discontinued, and I am searching for a suitable sustitute.

    I know that most of the chemistry manufacturers recommend dry nitrogen. The problem here is a source of dry nitrogen. So far, the only one I've found would be
    a supplier of industrial gasses - an entire "tank" for $LOTS.

    Somewhere, I've read that the suppliers of fine wines carry spray cans of argon, for displacing the oxygen in partially filled wine bottles.

    Anyone here have any knowledge of argon - which I undersatnd is an inert gas - and its probable effects when used to preserve photographic chemistry?
    Or another suitable replacement for "Protectran" or dry nitrogen?
    Carpe erratum!!

    Ed Sukach, FFP.

  2. #2

    Join Date
    Dec 2002
    Shooter
    Large Format
    Posts
    6,242
    Ed,
    If you have a window manufacturer near you they will probably use argon and possibly other inert gases as a UV shield gas for use in "Low E" windows. I would think that any of the gases in the argon, xenon, nitrogen, possibly even helium class would work as a shield to slow oxidation of the chemicals.

    As an aside, I have heard other photographers that use marbles in their partially filled chemical bottles to displace the liquid enough to limit the inclusion of oxygen through partially filled bottles. I have seen marbles that are used in some of the crafts in craft stores. Not sure if they are glass, though.

    Good luck, let us know what you come up with.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

  3. #3
    DKT
    DKT is offline

    Join Date
    Sep 2002
    Posts
    504
    well, the good news is that a tank of nitrogen should last you a lifetime....fwiw, we use "hospital grade" nitrogen with our Wing Lynch machine for doing E6. Nitrogen comes in different grades, and some of it can have small amount of oxygen mixed in as well.... I messed up once & ordered a lower grade of nitrogen and the chemistry really suffered--live & learn. I would think (don't know though) that you could get a smaller tank-size? I've seen photos of a portable WL machine once--that was the top part of model 4E fitted into a truck. If I remember correctly, the picture I saw had a small nitrogen tank lying alongside it. About the size of a scuba tank. Kreonite and some other manufacturers make nitrogen generators for the lab industry though, but I know they cost $$$$ compared to just getting the tanks...once you pay the deposit, the price of the gas really isn't that much. If you actually use it up, the next tank is alot cheaper...we use about 2-3 a year, but I think for what you're doing a tank would last forever almost. can't help you on the argon though, every lab I've ever been in has just used nitrogen.

    KT

  4. #4
    clogz's Avatar
    Join Date
    Dec 2002
    Location
    Rotterdam, The Netherlands
    Shooter
    Multi Format
    Posts
    2,837
    Images
    114
    Surprised to hear that Tetenal has discontinued Protectan. Used to be good stuff.
    In olden days photographers used socalled photo ether to keep their chemicals.As such this is no longer produced by the photo industry but...could'nt we just use normal ether?

    Does anybody know?
    Digital is best taken with a grain of silver.

  5. #5
    b.e.wilson's Avatar
    Join Date
    Sep 2002
    Location
    Provo, Utah
    Shooter
    4x5 Format
    Posts
    141
    The difluoroethane in products like "Dust Off", typically used to move dust off film and into the air, is unreactive and will displace air quite nicely. You can even invert the can and spray some liquid into a bottle and cap it as it evaporates to displace even more oxygen (just pointing the nozzle into the top of the bottle and shooting gas in always brings more air with it). Just be sure not to cap it before the bulk of the liquid has evaporated and displaced the oxygen, and never do it with a glass or other rigid bottle.

  6. #6
    Ed Sukach's Avatar
    Join Date
    Nov 2002
    Location
    Ipswich, Massachusetts, USA
    Shooter
    Medium Format
    Posts
    4,520
    Images
    26
    I contacted JOBO tech for information on a "Protectan" subtitiute - got a "You're on the List" answer ... so I'm waiting.

    While I was there, I mused about and came up with this information from their "Support" section ... "JOBO Quarterly - Issue #4 - JQ9404." This was written by Paul Rowe, a much missed member of the JOBO organiztion who passed away a few months ago.

    The article was titled: "Color Negatives - The C41 Process".
    Paul had conducted quite a bit of research into the process, with specific consideration to uniformity and consistency of processing - these were his conclusions:

    1) Pre-wet of the film produces unpredictable variations.

    2) Acid stop bath introduces unpredictable variations.

    3) Rinse (using water instead of stop bath) after the developer introduces unpredictable variations.


    All of which seems to agree with my own experience, although I haven't been anywhere near as thorough as Mr. Rowe was.

    The *ONLY* place I use stop bath now is in RA-4 Color Printing... I believe it *IS* necessary there.

    I know it is risky to try to extrapolate this to Black and White processing - but I think there may very well be valid parallels there.

    Comments?
    Carpe erratum!!

    Ed Sukach, FFP.

  7. #7
    Aggie's Avatar
    Join Date
    Jan 2003
    Location
    So. Utah
    Shooter
    Multi Format
    Posts
    4,925
    Images
    6
    ..

  8. #8
    glbeas's Avatar
    Join Date
    Sep 2002
    Location
    Roswell, Ga. USA
    Shooter
    Multi Format
    Posts
    3,307
    Images
    109
    I've never presoaked a piece of film in my life. Never had a problem with it. What happens with you Aggie?
    Gary Beasley

  9. #9
    Aggie's Avatar
    Join Date
    Jan 2003
    Location
    So. Utah
    Shooter
    Multi Format
    Posts
    4,925
    Images
    6
    ..

  10. #10
    glbeas's Avatar
    Join Date
    Sep 2002
    Location
    Roswell, Ga. USA
    Shooter
    Multi Format
    Posts
    3,307
    Images
    109
    I think that would happen with me if I got the developer into the tank too slowly. Does this happen with all film developer combos? All tanks? Then maybe the stuff I shoot just never shows that kind of defect off. It *is* kind of odd how that happens.
    Gary Beasley

Page 1 of 8 1234567 ... LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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