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  1. #71
    CMB
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    Quote Originally Posted by gmikol View Post
    Are the UltraStable tissues as sensitive to differences in ambient humidity as dichromate-sensitized tissues?

    --Greg
    Changes in ambient humidity and temperature have little effect on the sensitivity of the UltraStable pigment films. Furthermore, Dark Reaction, the spontaneous hardening of dichromate sensitized films, is practically non-existant with gelatin layers sensitized with Azido compounds. Another problem with dichromate sensitization, post-exposure variations in densities if not processed immediately, is also a non-problem with the UltraStable films.

  2. #72

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    Quote Originally Posted by gmikol View Post
    Most carbon printers know (or at least should know) that dichromate-sensitized tissues are quite sensitive to relative humidity (or more properly, the moisture content of the tissues), which affects speed and contrast.
    --Greg
    Off topic a bit.

    Well, I just learned that the hard way. Recently used three tissues I made a few months ago. Had good notes from my initial prints. Used the exact same negatives, sensitizer & exposure times. Now wanting to make the most of my limited time, I exposed & mated all three.

    Upon development - No tone/paper white until around what should have been zone 7. OOPS

    But I fixed the blister problem

  3. #73
    Philippe Berger's Avatar
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    No problem with the use of potassium dichromate to sensitize the Carbon Tissue BUT
    I make myself my Carbon Tissue for use in 8 days
    I always use fresh potassium dichromate
    I do not include potassium dichromate in the formula of carbon tissuer
    I cupped awareness but still the same concentration, the same temperature, the same time awareness, the same drying time, the same humidity
    I use always the same formula of Carbon Tissuel in eight days of its manufacture
    I always use the same kind of digital negative with Software appoints an application that I created for Carbonl
    My exposure time is always the same, I confirm

    This just to say my personal experience but I'm just practicing as a small amateur photography Carbon

  4. #74

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    Quote Originally Posted by CMB View Post
    Changes in ambient humidity and temperature have little effect on the sensitivity of the UltraStable pigment films.
    Thank you, Charles!!

    --Greg

  5. #75

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    Quote Originally Posted by R Shaffer View Post
    Off topic a bit.

    Well, I just learned that the hard way. Recently used three tissues I made a few months ago. Had good notes from my initial prints. Used the exact same negatives, sensitizer & exposure times. Now wanting to make the most of my limited time, I exposed & mated all three.

    Upon development - No tone/paper white until around what should have been zone 7. OOPS

    But I fixed the blister problem
    That's a huge change in sensitivity. I always thought that the influence of humidity/moisture was maybe +/- 1 stop. Not the huge change you saw.

    At the risk of going further off-topic, it makes me wonder whether something else changed between then and now. Sensitizer measurement error, bulb aging, etc.

    --Greg

    PS--Rob, if you want to discuss this further, we could probably have the mods split this off into a separate thread.

  6. #76
    holmburgers's Avatar
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    Greg's post in the diazo thread just made me think of this.

    Could I substitute dichromate for permanganate in the clearing bath A?

    I know, the irony is terrible... but I don't have any permanganate on hand and wouldn't mind clearing the print I have.

    Thanks guys
    If you are the big tree, we are the small axe

  7. #77
    Photo Engineer's Avatar
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    I have no idea.

    PE

  8. #78
    holmburgers's Avatar
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    I just thought that the powerful oxidizing nature would do the same thing as permanganate, just like in reversal processing.
    If you are the big tree, we are the small axe

  9. #79

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    Quote Originally Posted by holmburgers View Post
    Could I substitute dichromate for permanganate in the clearing bath A?

    I don't have any permanganate on hand and wouldn't mind clearing the print I have.
    Don't know about dichromate, but I just tried hydrogen peroxide. Some web reading suggested that it's oxidizing ability was enhanced in acid solutions. I only had 3% stuff around (drug-store H2O2), so here's what I tried:

    100mL 3% H2O2
    ~1mL 40% citric acid solution (this is about 0.4g).

    It created a just-noticeable lightening of the dye stain in an all-white area (drop test) after about 90 seconds contact. Perhaps if you can easily get your hands on 10% or stronger H2O2, it might be a viable option, and one that eliminates the need for potassium permanganate.

    Good luck--

    Greg

  10. #80
    holmburgers's Avatar
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    Thanks Greg, I might have to give this a shot. I do love grocery store photo chemistry!
    If you are the big tree, we are the small axe

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