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  1. #11
    Neanderman's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    There's a 2nd edition of that book
    Wiley published what appears to be a 3rd edition, "Introduction to photographic theory", by Carroll, Higgins & James, 1980. (I say this appears to be a third edition because on the rear DJ overleaf it says that Higgins "co-authored the first two editions of Fundamentals of Photographic Theory.

    I have a copy and will look through it to see if it adds anything.

    Ed
    "I only wanted Uncle Vern standing by his new car (a Hudson) on a clear day. I got him and the car. I also got a bit of Aunt Mary's laundry, and Beau Jack, the dog, peeing on a fence, and a row of potted tuberous begonias on the porch and 78 trees and a million pebbles in the driveway and more. It's a generous medium, photography." -- Lee Friedlander

  2. #12
    Photo Engineer's Avatar
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    That is very odd. I knew Burt much better than the other two and he never mentioned that to me. There is no mention of that in any of the books I have either.

    I've mentioned elsewhere that Burt and his wife used to vacation at Letchworth state park where we also used to stay at the Glen Iris inn. We spent many hours together on the front porch discussing photo theory and product design. This is one thing that he never mentioned even though James and Higgins often came up in our conversations.

    PE

  3. #13
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    To further this discussion about gelatin, first off in the OP I mention the remarks about gelatin. Well, in the section on ripening the authors refer to using an inert gelatin to make the emulsion and an active gelatin to finsih the emulsion after washing. They give no details, but Kodak engineers and Agfa engineers among others knew of at least 3 if not 4 types of active gelatins. So the subject was quite well known at the time.

    Now, to move to modern times we see somewhat the same thing. I have been buying brand "A" inactive oxidized gelatin and recently changed to brand "B" inactive oxidized gelatin. I observed a 1.5 stop speed loss in my Azo type emulsion!

    This indicated to me that there is a change in the emulsion introduced by some ingredient in the gelatin so I heated up emulsion A and B and then coated immediately. I also coated at 2 hours and 8 hours with constant heating at 40 deg C applied for all of this time.

    The results are in the photos attached.

    The surface defects you see are artifacts due to being coated on unsubbed paper. The sample photo on the left shows gelatin A and B side by side fresh, and the sample photo on the right shows gelatin A and B side by side after 8 hours holding in the sink. It is evident that sample B did not change in fog substantially but did gain a bit in speed and/or contrast over 8 hours. This indicates 2 things to me.

    One is that gelatin A has a weak ripening agent in it and is not truly a pure oxidized photograde gelatin as we know it today. It is a weak ripening gelatin as was known 50 years or so ago. It causes fog as well as increased speed.

    Second is that gelatin B has no ripening agent.

    Finally, the emulsion B, through the small change it undergoes, tells me that I need more stabilzer or a longer ripening time during the original make (or both).

    Since my coating sessions rarely last more than 2 hours, I saw little or no change with respect to hold time from either A or B in normal coating sessions, but I did see the unexplained speed difference in fresh coatings, and this long keeping test revealed the reasons for the speed difference.

    Gelatin B is Kodak photograde gelatin and is sold by the Photographers Formulary. IDK who else sells this, but I have verified it with them.

    They change to Gelatin B, when I began to have hints of problems last year with Gelatin A. Gelatin A is still a good quality product, it is just different. And so, to make an emulsion using the methods of James and Higgins, one might precipitate an emulsion with gelatin B (Kodak) and then add A to make up to final coating weight and hold for 1 hour or more at 40 - 60 degrees C as described in the text.

    This will conclude my tests, as it is much preferred to use a gelatin of type B (Kodak) and add the precise amount of sulfur containing agent rather than rely on a gelatin to supply it, as the amount of sensitizer might vary too much and would take extensive tests to qualify a gelatin of type A to be useful.

    PE
    Attached Thumbnails Attached Thumbnails 2 gelatins fresh.jpg   2 gelatins held.jpg  

  4. #14

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    Black Magic?

    [QUOTE=Photo Engineer
    I have been buying brand "A" inactive oxidized gelatin and
    recently changed to brand "B" inactive oxidized gelatin...
    Gelatin B is Kodak photograde gelatin...
    Gelatin A is... a good quality product... just different.
    PE[/QUOTE]

    What was Gelatin A?

  5. #15
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    Quote Originally Posted by Ray Rogers View Post
    What was Gelatin A?
    Ray;

    I don't feel comfortable posting the name publicly. I am concerned thought about differences between this gelatin and the Kodak variety in other alternative processes.

    PE

  6. #16
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    Ron,

    A question about your statement: "The surface defects you see are artifacts due to being coated on unsubbed paper." The only commercially available 'subbed' paper I'm aware of is the glossy baryta that The Formulary sells. Is there another? Or, are you normally subbing watercolor paper before you coat?

    Which paper are your tests printed on? If it is cold press Strathmore, you might consider changing to something smoother or giving your coating bar a bit more of a gap. I know you like the heavier paper because it dries flatter, but I think you'd have better luck judging the density range on a smoother paper. Fabriano Artistico HP works well. And for the purpose of jpeg illustrations, the PF baryta might be best.

    Also, re the various gelatins out there: People may have missed what I think you meant to say - that most problems with materials (and the absolutely inevitable mysteriously-changing-product phenomenon) are alleviated by an intimate knowledge of your process, whichever it may be. With practice and familiarity, it's easier to do tweak-arounds.

    d

  7. #17
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    Denise;

    This is a Strathmore hot press paper. The defects are not visible to the naked eye as such. Rather, the paper has a pleasing tapestry like look and feel. The scanner magnfies this. You have seen some samples like this at the workshop and the above ones look no different (fresh) in the dmin area.

    PE

  8. #18

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    Rhetorical Qs about Gelatin X

    Quote Originally Posted by Photo Engineer View Post
    Ray;

    I don't feel comfortable posting the name publicly. I am concerned thought about differences between this gelatin and the Kodak variety in other alternative processes.

    PE
    Ron,

    By other alternative processes, it sounds like you mean non-AgX processes like carbon tissues, cyanotype or even perhaps AgX Matrix film....

    I wonder if a simple description of the material and the behaviour you are concerned about would not be sufficient to protect those other alternative-process users?

    If "Gelatin A is still a good quality product... just different."
    Seems unnesessary to neuter the nomenclature.

    What promted the change to Gelatin B anyway?

  9. #19

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    Quote Originally Posted by Ray Rogers View Post
    If "Gelatin A is still a good quality product... just different."
    Seems unnesessary to neuter the nomenclature.

    What promted the change to Gelatin B anyway?
    I think it's that Gelatin A fogs and is not truly inert - as it should be and for which it was being sold as. While Gelatin B is inert.

    I think I would have to disagree with the statement that it is a "good quality product" if it did not meet one of the primary characteristics it was supposed to have.

    It still can be used for other uses for which gelatin can be used, but just not as inert gelatin.

  10. #20
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    I have described the differences above. Higher speed with gelatin A, and a high tendancy to go into fog with keeping. Those reasons assisted me in suggesting the change! My guess as to higher quality was paramount in this suggestion. I have tested several gelatins from different companies. My recommendation is Kodak gelatin, 250 bloom photo grade bovine oxidized and deioinized.

    PE

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