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  1. #71
    Hexavalent's Avatar
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    Hi Bill,

    I though of treating some imagesetter film with dye, but there's no practical way to get the goods into the film. It's designed for very rapid processing (under 1 minute), and as such the existing dyes, anti-halo etc., wash out if one tries to soak it in erythrosine (or other) solution.
    Imagesetter film doesn't make a very good camera film, but it does make a very durable film base if it's fixed and washed
    - Ian

  2. #72

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    Handmade Gelatin Dry Plate Making August 18, 2014 through August 21, 2014

    Can anyone confirm that participants will actually coat, expose, and print plates during the 2014 Handmade Gelatin Dry Plate Making Workshop?
    The course description indicates that students will make a silver bromide emulsion suitable for plates to be used in the camera but does not mention the experience of coating, photographing, and printing. Is this a separate workshop?

    The 2013 workshop looked most interesting.

    Regards,

    George

  3. #73
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    George, they did all of it in previous workshops. From start to finish.

    PE

  4. #74

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    Thank you.

    By the way I purchased your book and DVD's - I'm Hooked! I first developed film and enlarged photos in 1970. In 2010 I purchased a Crown Graphic on Ebay and rejoined the hobby. I really missed the hobby for all of those years. As a Chemical Engineer the topic of VAg and the science behind it is interesting. I have found several patents, applications and papers from RIT that describe the process. I have also read all of your posts on this site. I have even obtained the Computer programs Kodak once used to control the reaction - fascinating stuff.

    I hope to make the August Workshop. My wife suggested it as a Christmas gift.


    Regards,
    George

  5. #75
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    What is the name of the conputer program? Just curious as there were several due to having some computers obsoleted. They also differed according to scale.

    There was also a set of programs that allowed for the design of emulsions in the office which then wrote code for the various computers.

    Thanks for buying the book and DVD. I hope it works out well for you. The RIT papers are not as "deep" as the patents. I suggest some of the patents in the book by Lin et al. And Judd et. al. In some of them they are co-inventors.

    PE

  6. #76

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    Photo of all the finished glass plates on GEH course

    Click image for larger version. 

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    Russ

  7. #77

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    The computer code that provided the most complete information of how the process worked is titled “COMPSELECT”. From this reference, the RIT papers, and other patents, I was able to cobble together the parameters for controlling the Crystal Habit from CubicCubo-octahedralOctahedralTabular. The targets were given for the initial potassium bromide concentration, temperature, along with the minimum and maximum bromide concentration breakpoints for each crystal habit zone. The formulas for the Nernst and Debye Huckle equations were embedded as well. The code also contained two-point calibration checks for the silver billet electrode. From all of this I was able to extract enough information to gain an understanding for controlling the silver ion concentration during the precipitation by modulating the salt and silver jet flow rates under PID control and ramp segments. The evolution of this process from the art of making silver halide emulsions to the science of making them is interesting.

    George

  8. #78
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    George, much of the details and references are also in my book, as you know.

    COMPSELECT was written in QNX and so would have to have a bit of translation. It was replaced by MERLIN. Also, there were programs for the Taylor, Siemens and WDPF computers.

    There are patents on the Debye Huckle and Nernst equations. Lots of detail.

    BTW, click on the title of a workshop in the GEH list and you get an expanded description of the course.

    PE

  9. #79
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    George, I can find no on-line reference to COMPSELECT.

    PE

  10. #80

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    COMPSELECT

    Ron,

    This program is written in BASIC. It contains routines for selecting the Halide type: Br, I, and Cl and allows the user to enter a make with up to 15 segments in the flow-profile with holds.

    It has ability to pre-heat the z-batch and utilizes both shallow and deep temperature sensors. It also has routines for storage and retrieval of the various “makes” should you want to repeat a particular flow profile. There are also subroutines for VAg calibration whereby the silver billet, triple junction reference and temperature probes are immersed in standard solutions and checked for proper operation.

    There are detailed error routines for detecting any drift along with suggested possible causes such as noisy signals caused by faulty connections, plugged junctions, leakage rate of the salt bridge solution and poorly platted silver electrodes. It offers corrective actions to replate the silver billet electrode, and replace the lower bridge junction. This combined with the RIT papers and your many posts on VAg have given me a clear understanding of the topic. All-in-all, it lays out the details necessary to construct a working system migrated to todays programming languages and single-board microcontrollers.

    On a related thread you mention the need for higher purity silver for the electrodes and importance of the uniformity of plating. I purchased two lengths of high purity silver rod, diam. 7.0 mm, 99.99%, Sigma-Aldrich item number 26,562-4 (10 grams = 25 mm or 40 grams = 100 mm) for fabricating the silver Billet electrodes. I am planning to round-off and polish the end of the rod to achieve a "bullet" geometry and mount it in the end of a Teflon rod prior to plating. I hoping this smooth-surface geometry will improve the uniformity of plating over wire-type electrodes.

    George

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