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  1. #1

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    Antihalation coating

    What can I use on the back of my plates for antihalation ?

  2. #2
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    Hi! Kevin,

    Nice to see you here again. Does this mean you're back in the dry plate game? As I think you know, someone is having great fun and very reasonable success with your emulsion recipe right now.

    Try this for halation. It's not near as fiddly as it looks at first glance and once you've made the sheets, they can be used over and over again.

    http://www.thelightfarm.com/cgi-bin/...tent=28Apr2011

    d
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

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    Kevin;

    If you are using the old glass plate holders with the red sheet in the middle of the holder (it is usually wavy and not flat), this will serve as a good AH backing for slow blue or ortho plates. This is especially true if your subject is not back lit.

    If you want to go "all the way", then the old guys back 100 years or so ago, got an oxonol dye, which is yellow orange. They coated the backs of the plates with the dye in gelatin and it washed off during processing. Often it was totally removed as they did not harden the gelatin.

    Almost any orange dye can be used, such as a mix of Solantine Pink and Solantine Yellow. You can use food dyes which are really often Solantines.

    PE

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    Thanks for the welcome and backing ideas. I had thaught of just putting a piece of red paper behind the plate.

  5. #5
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    That should work! Bud, as noted above, you may not need it.

    PE

  6. #6
    dwross's Avatar
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    I've run plates through holders with red septums and black septums (the middle, backing part of a holder) and never found that the red does much to help. The problem is that the backing has to be in close enough contact with the back of the plate that there is no air space. In the early days the solution was usually lampblack or caramel coloring in gelatin or reusable applied sheets. The right dyes in gelatin came a little later and probably work the best, but whether or not more so enough to be worth it is certainly a matter of taste and not of necessity.

    There are good illustrations of both irradiation and halation at toward the bottom of this page.
    http://thelightfarm.com/cgi-bin/html...tent=04Dec2011
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

  7. #7

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    hi denise

    i went to your first link and you mention the use of collodion as an AH backing.
    from personal experience when the colodion is dry inks seep in and are part of the
    celluloid and it probably will work very well as a AH backing ... it's rigid too,
    and the cheaper-stuff ( flexible with lanolin i think ) can be bought at some pharmacies.

    i never really like working with collodion mainly because of the vapors and how flammable it is.
    while it would work well and absorb pretty much any ink (or paint i am guessing) once it is dry
    and it can be easily peeled off by poking up a corner and peeling off the plate, personally i'd use something else
    cause i am not really a fan of such flammable stuff. .. after you peel it off, what would do with it then?
    can't really dispose of the stuff in the trash, have it too close to a light bulb and you have a 2nd cleveland clinic fire

    maybe just make a few of them and just reuse them ?

    have fun !
    john

  8. #8
    dwross's Avatar
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    Hi John,

    Thanks for the voice of experience! I never got around to testing collodion. I ordered a small bottle but when i opened it, it smelled so dreadful that I closed it right back up! The press-on black sticky sheets were working so well that I couldn't find the motivation to test collodion just for the sake of testing. I'm still reusing the ones I made way back then -- that is when I'm actually worried there might be halation. It doesn't happen in every and all shooting situations. I've pretty much figured out when to bother. The nice thing about the sheets is that you just pull them off before processing the plates. There's no gunk that gets carried into the developer.

    I've been doing at least 75% of my work on film for over a year. Film (at least the Grafix Dura-lar Wet Media) is very hard to get halation on, even if you want it for artistic purposes.
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

  9. #9

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    the collodion might work well with your film, if you decide you don't mind all that ether and the feeling of
    being a madscientist ... you would just bow the film and have it "kiss" the collodion ..
    but then you'd have to do it someplace ventilated, before you add your emulsion to it, and removing it
    might be as simple as with the glass. when i used it i'd pour it into a little plastic mold, and it came off the
    plastic pretty easily ... i seem to remember putting on the back of photographic film too ( 4x5 olde tmy )it was OK ...
    another suggestion might be "water glass" the stuff the coat eggs with ( sodium silicate ) .. i haven't played with
    it in a long time, it might take inks and dyes too, and i know it isn't sensitive to temperature like collodion ...

  10. #10
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    Irradiation is a short and "improper" term for multiple internal reflections. It is caused by turbidity which is the opaqueness of the emulsion making it cloudy instead of clear. This is reduced by acutance dyes put into the emulsion. They are the things that wash out when you process commercial emulsions. They slow the emulsion down.

    AH layers, for all practical purposes, do not slow down an emulsion.

    Often, what appears to be "irradiation" or halation is caused by UV which varies with season, time of day and lens. Modern coatings contain UV overcoats to minimize or "nrmalize" this problem.

    The orance or black septom decreases the effect of back reflections, but as Denise points out, this is not complete.

    Collodion contains ether and is not recommended for the average household darkroom.

    PE

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