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  1. #1
    Nikola Dulgiarov's Avatar
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    Sensitizing already coated film

    I need help with a little experiment I plan to try:
    I have a thousand sheets of ORWO FU5, which is a very high contrast film used in the graphics industry, formerly made by ORWO. The film is pretty outdated( 1995) but has virtually no fog, or so I have found using it in a variety of situations. It has an unsensitized emulsion, and I use it at a sensitivity of 1.5-3 asa outdoors depending on light conditions. Inside, it's much harder, and with a 3000K continuous lighting setup I get an iso of around 3/8 of an ASA, the same I use for my collodion setup.
    Here;s what I want to try - get some erythrosine and mix a sensitizer such as presented in "The Photographic Negative" by Burbank. Basically it's a two bath process - an ammonia bath to swell the emulsion, ant the dye bath. I know the film has no overcoating or any dye added to it during manufacture - or so I am told.
    So the thing is - it it worth getting some erythrosine and possibly eosine to try to sensitize a film that expired the year I was born ?
    If so, any tips ?

  2. #2
    holmburgers's Avatar
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    Nikola,

    Worth sensitizing a film that expired in '95? That's a tricky question... but I think that your interest in bath-sensitizing coated film is very valuable and worth exploring.

    I have a description of panchromatizing an emulsion with erythrosine & get this.. a chrlorophyll tincture harvested from blue myrtle leaves! F.E. Ives did this in the late 1800's.

    This kind of experimentation would benefit the whole analog community. Imagine how great it would be if you could find a way to post-sensitize LiquidLight and other pre-made emulsions? This would open up a whole realm of interesting stuff...

    I think you'll have to do some original research & work though.. I don't believe anyone is currently doing this.

  3. #3
    keithwms's Avatar
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    What about hypering it. Maybe that will bring it back...?
    "Only dead fish follow the stream"

    [APUG Portfolio] [APUG Blog] [Website]

  4. #4
    Nikola Dulgiarov's Avatar
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    Ok, I'm going to do it for the sake of providing practical information as to whether it is a viable method of improving a film's spectral sensitivity(even a little bit). I've ordered 10g of erythrosine and will give it a shot ASAP. Till then, maybe someone with a similar experience can chime in

  5. #5
    Hexavalent's Avatar
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    I think this has been addressed elsewhere on APUG; sensitization of Liquid Light to IR if memory serves me.

    A few things to bear in mind: dye molecules need to be absorbed onto the silver for effective sensitization. Anti-foggants, stabilizers etc., already in the emulsion may prevent, or hinder this process. The same additives as well as anti-halation dye, acutance dyes may wash out during the swell-and-soak process. You might want to try the swell and soak without dye first, to determine if the emulsion survives the process.

    It might work. Worth a try anyway.

    Looking forward to hearing about your results.
    - Ian

  6. #6
    Nikola Dulgiarov's Avatar
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    Well, after getting two feet of snow this morning and school being canceled for the rest of the week, I decided I couldn't wait for the erythrosine to come from the other side of the country, I visited a local supplier and got a "sample" of erythrosine for the price of telling the guy if it worked or not
    So expect results soon...

  7. #7
    Nikola Dulgiarov's Avatar
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    OK, preliminary results...
    I got my erythrosine today and mixed a sensitizing bath as described in the book "The photographic negative". The first bath is ammonia, and the second is ammonia mixed with the erythrosine solution, in particular - 25mg of erythrosine in 200ml of solution.
    Now, there IS a boost of speed, which I judge to be about 1 2/3 - 2 stops, and a gain in the green sensitivity. However, in the rush I underexposed the test sheets by about a stop, so I can't be objective( I know...I'm very poor at being methodical). Exposed through a 85B filter, which is the only orange/red filter I had, the unsensitized emulsion is very very slow, but the film I bathed in the sensitizer developed normally.
    EDIT: I forgot to mention my little neanderthal test was done under two 2800K floodlights.
    I don;t have a scanner right now, but when I get home, I'll scan them.
    Last edited by Nikola Dulgiarov; 02-07-2012 at 01:04 PM. Click to view previous post history. Reason: add info

  8. #8
    Photo Engineer's Avatar
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    What Ian said above is quite true. An emulsion with all finals in it for keeping is hard to sensitize. OTOH, the Ammonia will move things along. OTOH again, Ammonia, as a silver halide solvent can have speed effects of its own. So, this is a really hard call. Try making an exposure through a green filter using film before and after sensitization. One will be blank and the other should have some image.

    PE

  9. #9
    Nikola Dulgiarov's Avatar
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    Thanks mr. Mowrey, I also suspected ammonia as a cause for the speed increase. I wanted to ask about erythrosine's sensitizing ability - what is its peak wavelength? Also, would a yellow filter work, or is is too far? I'll try immersing the film at time intervals in the dye solution to see what factor does soak time have on the final result. I presume that it would take longer for the dye molecule to enter the emulsion in depth and... attach itself to the agX...when the film has been kept for a long time and probably factory hardened. Burbank suggests a soak time of 60 - 90s, but a fresh emulsion would accept the dye more readily, no?

  10. #10
    Photo Engineer's Avatar
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    Erythrosine peaks at about 540 nm but depends on halide content giving slight shifts and changes in bandwidth. It depends on the yellow filter as to whether you can use one. Remember that Erythrosine is not recommended for Ag/Br/I emulsions by Mees, but old reports show it works well when added before precipitation. I suspect that the Ammonia is redissolving enough Silver halide to reform an Erythrosine-Silver salt or complex.

    I've discussed this with Paul Gilman a while back and he is of the opinion that it has not been studied enough as it is such a poor dye in general. So, he had no real opinion on its use.

    Best of luck.

    PE

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