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  1. #1

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    Color Paper Top Emulson Layer

    Most of the color papers are coated with various top emulsion cover. For Fuji, it is blue layer.

    What does it do? If I understand it correctly, during the pre-wash, this layer is washed away, and the entire emulsion is ready to accept developer chemicals. So it appears this top layer is mainly for protection?

    The reason for my asking is that, when I was doing my test printing last time, some of the test strips came out with the un-exposed paper in fainted blue color. That is the same color of the original Fuji color paper. So the top layer was not completely washed away. When I processed the test strips, I pre-wash with warm water for 30 seconds. Then 50 seconds developer and 60 seconds blix. I skipped the final rinse stage and washed the strips in tap water. I normally wash the final prints with rinse chemical for 2 minutes.

    I never had the same problem before. So I do not know what had happened. Paper coating change, or chemical change?
    A photo amateur
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  2. #2
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    You completely misunderstand the layers in color paper.

    The structure is /overcoat/Cyan (red sensitive)/interlayer/Magenta (green sensitive) / interlayer/Yellow (blue sensitive)/RC/paper/RCbacking

    The paper has this layer order for image stability and sharpness. It contains dyes to also improve sharpness and these dyes wash out during processing. No layer washes off.

    If unexposed paper has a blue color after processing, then it was fogged with a red safelight.

    PE

  3. #3

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    PE, I do not think you understood my question.

    It is the top layer (or overcoat) I was asking. For Fuji paper, it is light blue. During the pre-wash, I can see clearly that the rinse water came out to be blue. Over time, developer becomes dark, mainly due to the blue color too.

    I do not use any safelight with color printing. I've done color printing many times with the same paper, so I know this paper is good. So when the un-exposed paper turns to light blue, I know it is the top layer of the Fuji paper. It was not washed or rinsed properly. This is the first time happened to me and I do not know just why.

    To make this go away, I'll have to extend the pre-wash time, or wash the paper with RA-4 rinse. I skipped the rinse stage just because this is only test strip. So it appears I can't skip the final rinse stage.

    Hope I could have made things a lit more clearer.
    A photo amateur
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  4. #4
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    The bluish color of all color papers is due to a dye in ALL of the layers. It is there to adjust speed and to improve sharpness. This dye gradually builds up in the color developer (if you reuse it) and the developer becomes darker and darker blue. Of course, if you follow the published guidelines, you will know if you are putting too much paper through the developer.

    In any case, the blue dye is never retained in the coating, nor can it dye the coating blue. Something else causes that blue color. I mentioned red safelight fog. It can also be caused by contamination of the developer with blix, and by omission of the stop bath after the color developer.

    If you have leftover dye in the coating (blue dye that should wash out), then a simple re--wash should remove it, but I suspect that you have some other problem. I mentioned several above here.

    The overcoat, as I tried to explain in my OP is just plain gelatin! If it is matte paper, then it also contains a matting agent to make the paper have a rough surface. And the dye is uniformly distributed throughout the coating in both Kodak and Fuji papers.

    PE

  5. #5
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    The Kodak papers we have are a brown/tan colour, Fuji is blue.

  6. #6

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    The blue top layer of Fuji paper is not part of the Dye. It is washed away in pre-wash. It appears to be protective coating, and indicator of the emulsion side of the paper. It is mentioned somewhere that I can't remember. This is the main reason that I'm asking.
    A photo amateur
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  7. #7

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    Quote Originally Posted by RedSun View Post
    The blue top layer of Fuji paper is not part of the Dye. It is washed away in pre-wash. It appears to be protective coating, and indicator of the emulsion side of the paper.
    I worked on Ektacolor paper for 5 years (in the '70s) and it was made like PE says. I can't imagine any reason for a 'protective coating' or an 'indicator of the emulsion side of the paper'; especially in a layer that washed away.


    There might be some specialized material for aero use (or something) that behaves as you describe.

  8. #8

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    Well, anyone who uses Fuji paper can pitch in. My RA-4 process is 30 sec pre-wash, 50 developer, 60 blix and 2 min RA-rinse. After my pre-wash, the water comes out blue. If this is final large print, the water comes out really blue. That is even before any chemical is poured in.

    The last time, when I processed the test strips, I skipped the final 2 min rinse stage. And the test prints came out with the un-exposed part blue, just the same color as the new paper, just lighter. And the edges where the prints attached to the print drum had darker color (blue). It apparently that the test prints were not washed/rinsed properly. So the original blue coating is still on the paper. The un-exposed paper should came out white, just as I had it many times before....
    A photo amateur
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  9. #9

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    I think the distinction may be between 'washed OFF' and 'washed OUT'. As PE has said, the blue appearing dye washes OUT during processing. No gel layer is washed OFF. If your prints weren't properly processed, some of the dye may remain. Did you try additional washing?

  10. #10

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    We are talking completely different thing. This blue color coating (whatever it is) gets washed away during pre-wash, even before developer is poured in. It has nothing to do with any dye.... Do not need to get in developing or processing.
    A photo amateur
    Sinar P2/F2/Nikon F100/Bronica ETRSi/GS/Saunders 4550XLG/Jobo CPP2/CPE+/Colorline 7000

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