Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,941   Posts: 1,557,562   Online: 1121
      
Page 5 of 6 FirstFirst 123456 LastLast
Results 41 to 50 of 54
  1. #41
    Rudeofus's Avatar
    Join Date
    Aug 2009
    Shooter
    Medium Format
    Posts
    1,696
    Images
    10
    Quote Originally Posted by john_s View Post
    And a sodium sulphite rinse, with maybe a pinch of metabisulphite and citric acid is very cheap and known to work.
    It is well established that hypo clearing bath helps in washing out Thiosulfate (and possibly its insoluble Silver complexes), but what Doremus understandably challenges is something different: that a wash step in hypo clearing agent after fixing allows a single bath fixer setup to process as many sheets as normally a two bath fixer setup.
    Trying to be the best of whatever I am, even if what I am is no good.

  2. #42
    Rafal Lukawiecki's Avatar
    Join Date
    Feb 2006
    Location
    Co. Wicklow, Ireland
    Shooter
    Multi Format
    Posts
    737
    I guess we are at the point that only testing will help reject the null hypothesis.

    I'll try to devise a test, and hopefully, run it, but it'll have to wait till I'm back from my upcoming US trips. Late April or even May... I want to run the tests on what some here called an "exhausted" fixer, or which I think is at the borderline, 2g/l, accumulated through a normal use.
    Rafal Lukawiecki
    See rafal.net | Read rafal.net/articles

  3. #43

    Join Date
    Sep 2002
    Location
    Oregon and Austria
    Shooter
    4x5 Format
    Posts
    848
    Quote Originally Posted by Rafal Lukawiecki View Post
    I guess we are at the point that only testing will help reject the null hypothesis.

    I'll try to devise a test, and hopefully, run it, but it'll have to wait till I'm back from my upcoming US trips. Late April or even May... I want to run the tests on what some here called an "exhausted" fixer, or which I think is at the borderline, 2g/l, accumulated through a normal use.
    I imagine the test should be fairly straghtforward. Simply fix a prints in a single fixing bath, do not use a wash aid, wash them thoroughly (overkill here to be sure) and subsequently test them sequentially for residual silver with ST-1. (I know ST-1 test doesn't really give quantifiable results, but it should work for comparison purposes). To really be accurate, you should fix unexposed paper of the same type and size. Unusably expired paper would be ideal for this if one had, or could get it. You should also fix for the same time

    Then, simply note how many prints go through the fix and wash until the stain appears. Now, repeat the experiment adding the wash aid. See if the number of prints that go through the process before the telltale stain appears is significantly more.

    To keep from using lots of unexposed paper, one could use 250ml of Ilford Rapid Fixer in an 8x10 tray, which would, if using paper with developed silver images on it, have a capacity (using Ilford's numbers) of 10 8x10 at a "commercial" level of permanence and 2.5 8x10 at the "optimum permanence" level. However, since undeveloped paper is being used, and there is no image silver formed, the capacity should be significantly less due to the increased amount of undeveloped halides, maybe even less than 50% of the throughput recommendation.

    I don't know how sensitive ST-1 is, so each print from beginning to end should be numbered and tested, stopping when a few prints show increasing levels of stain from the ST-1 test.

    The level of permanence when the stain appears is irrelevant to the experiment; just use the number of prints made before the stain appears as a basis for comparison. If a wash aid really can increase a fixer's capacity by 4x, then one should be prepared to fix four times the sheets used in the first part of the experiment during the second. (I still cannot see how this would be possible...)

    If the wash-aid increases capacity by a lesser amount, that should be apparent as well.

    Best,

    Doremus
    Last edited by Doremus Scudder; 03-24-2013 at 05:48 AM. Click to view previous post history.

  4. #44
    Rudeofus's Avatar
    Join Date
    Aug 2009
    Shooter
    Medium Format
    Posts
    1,696
    Images
    10
    Note that fixing has more variables than just the amount of chemistry that's in the bath: agitation, paper type, emulsion type, ambient temperature, freshness of fixer, ... getting reproducible numbers might be quite a challenge unless one creates very reproducible start conditions. This could also mean that in some instances we could fix much beyond the (most likely conservative) numbers given by Ilford.

    If you want to do reproducible tests I'd say you prepare AgCl and AgBr (from AgNO3 + KCl/KBr + filtration + drying) and season the fixer with predetermined amounts of AgCl/AgBr. You don't need to prepare much seasoned fixer as you can test fixation and washing with small test clips. This test setup allows to to quickly determine how much Silver can remain in fixer for archival fixing with various fixing and washing techniques.

    Once you have these numbers, all you have to do is translate these back to your practical printing setup.
    Trying to be the best of whatever I am, even if what I am is no good.

  5. #45
    Rudeofus's Avatar
    Join Date
    Aug 2009
    Shooter
    Medium Format
    Posts
    1,696
    Images
    10
    Quote Originally Posted by Doremus Scudder View Post
    No, I haven't done serious testing and, if you read my posts carefully, you'll see that I've left the possibility open.

    However, the claim that Rafal refers to and that you reference above is found ONLY in the Ilford data sheet on processing black-and-white materials ( http://www.ilfordphoto.com/Webfiles/200621111117720.pdf ). Such a claim is NOT found in either the data sheet for Ilford Rapid Fix or Ilford Hypam.
    Because this issue is central to this thread, I contacted Simon Galley and asked him whether the information in this data sheet is still valid, i.e. whether use of a hypo clearing bath indeed allows four times higher reuse of single bath fixer. Here is his response (reposted with his explicit permission):

    Quote Originally Posted by Simon R Galley
    Our technical service stand by the statements, they have been verified and checked over many years.

    Simon ILFORD Photo / HARMAN technology Limited
    Trying to be the best of whatever I am, even if what I am is no good.

  6. #46
    Rafal Lukawiecki's Avatar
    Join Date
    Feb 2006
    Location
    Co. Wicklow, Ireland
    Shooter
    Multi Format
    Posts
    737
    I have just stumbled on one more reference which suggests that using hypo clearing agents extends archival capacity of the fixer from its, otherwise, measly equivalent of 10 8x10" sheets per 1 l. In Tim Rudman's "Toning Book" (2010, ISBN 1-902538-23-4) on page 156, chapter "Archival permanence", section "Hypo-Clearing Agents", 5th paragraph reads:

    Hypo-clearing agents play an important part in the archival processing cycle. Firstly, their use extends the archival standard fixer capacity of a single-bath fixer by about a factor of 4.
    Rafal Lukawiecki
    See rafal.net | Read rafal.net/articles

  7. #47

    Join Date
    Feb 2007
    Location
    Slovenia
    Shooter
    Multi Format
    Posts
    780
    Images
    9
    Hi Rafal, I can't see how this is possible. Is hypo able to dissolve Ag(S2O3)- ?

  8. #48
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,624
    Images
    1
    Quote Originally Posted by Rudeofus View Post
    IIRC there were published tests of the individual hypo clearing agents, and that Sodium Sulfite was deemed the best. What one will eventually use probably depends on availability and cost as much as on actual performance.
    I wonder if it were a benefit to use a mixture of different salts,totalling a 2%solution
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  9. #49
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,624
    Images
    1
    Tetenal sells test stripsto measure silver content.for me they worked far better than an iodide test solution
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  10. #50

    Join Date
    Jul 2010
    Location
    Southern USA
    Shooter
    Multi Format
    Posts
    3,956
    Does Rudman provide any scientific proof for his pronouncement?
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

Page 5 of 6 FirstFirst 123456 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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