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  1. #11
    htmlguru4242's Avatar
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    Wow, ISO 15, not too shabby. Any details on the emulsion?

    I wonder if reversal processing will boost the contrast like it tends to do for regular negative films?



    Keep up the good work!

  2. #12
    Photo Engineer's Avatar
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    I've been telling you guys that high speed isn't impossible. I have an ISO 400 - 800 emulsion in my head. I have not been able to make it, but when I do, it will teach me a lot on how to make it practicable in the home darkroom.

    PE

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    Cool job! Looks like nitrate going into decomposition!

  4. #14

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    Thanks for all the replies! The emulsion was the amonia digest one that PE posted a while ago. The only difference is that I used acetic acid to neutralise the amonia (have to admit that it was not too accurate... I was dropping acid till the smell of amonia disappeared). The AgNO3+Amonia @35C was added to KBr @45C during ~15min continuously (I used a micropump, just because I have one... but dropping would also work). I don't have the silver gelatin book, but I remember looking at it and in there I think they just inject the AgNO3 + amonia continuously over 30s.

    Then all the basic steps, then, before coating:

    Alcohol - .4 ml/10ml of emulsion
    Sorbitol - ~0.3g/10ml
    Sensitiser. I use quanidine red .2% and use about .05 to .1 ml/10ml
    Photo Flo - .4ml/10ml

    then coat (after bathing the polyester leader with NaOH for 5min and washing)

    Then hardening (using PE formula from a few posts ago).

    Here was my grief. Due to hurry and anxiety, I did not wait for the gelatin to dry completely before hardening it... So, my nicely coated film had horrible sections where it came off. The second batch (that I wanna process in reversal) survived the hardening process easily but I wait 1 day to dry before hardening it.

    Anyway, many thanks!

  5. #15
    Photo Engineer's Avatar
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    Ok, I think that is too much photo flo. I use 0.5 ml/100 ml of emulsion.

    But, most importantly, using that sulfur sensitization I described previously will probably boost your speed to over 25. I've gotten 40 in most cases. You will also get higher contrast.

    If you use the prehardener, it is a good idea to wash afterwards and then fully process the film. If the film is left in contact with the formalin overnight, it can fog the film. Formalin can do that. It depends.

    PE

  6. #16

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    Hi PE, thanks for the info. I'll put less photoflo

    but the formalin did not seem to fog it too much. I coated another film with chrom allum and I'll see how it goes. By the way, I just came from the dark room and developed some film stripes in reversal and it came positive (very low contrast though - will try longer 1st developer). Once it dries I ppost the pics. Cheers


    Quote Originally Posted by Photo Engineer View Post
    Ok, I think that is too much photo flo. I use 0.5 ml/100 ml of emulsion.

    But, most importantly, using that sulfur sensitization I described previously will probably boost your speed to over 25. I've gotten 40 in most cases. You will also get higher contrast.

    If you use the prehardener, it is a good idea to wash afterwards and then fully process the film. If the film is left in contact with the formalin overnight, it can fog the film. Formalin can do that. It depends.

    PE

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