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  1. #81
    holmburgers's Avatar
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    Greg,

    This sounds very cool!

    Would you concede that a reduction in speed is made up for by having presensitized "ready to go" tissues though? Then again, heat is a concern.

    Do you plan to repeat the same test with CAS 68988-17-0 to see how they compare?
    If you are the big tree, we are the small axe

  2. #82

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    Well, as mdm suggests, exposure times for separations would likely be much less. Using CMB's target of 1.24 logD for the black UltraStable tissues would probably mean at least 2 stops (if not 3) less exposure that what I did. So for separations, you're right about the trade-offs, pre-sensitized definitely wins. But I'd also like to use pre-sensitized tissues for B&W work, as well. In this case, sitting around for 20 minutes waiting for something to print is a bit of a PITA.

    I plan on making a test of the other sample eventually. It was similar enough to what mdm used, that I wanted to try the other one first. I only get little bits of time here and there over the summer, so it might be a while before I get a chance. I hope to get more time once the fall settles in.

    --Greg

  3. #83
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    I agree, it'd be nice to completely eliminate dichromates for b&w too. For what it's worth, my exposures with 2 CFL black lights can be about an hour long...
    If you are the big tree, we are the small axe

  4. #84

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    Well...I'll acknowledge the possibility that the bulb in my NuArc NL22-8C is at the end of its life. It's the bulb that came with it when I bought it used, and I have no idea how many hours it has on it. I have a replacement, but in an attempt to protect the upper safety glass from shifting / breaking since it gets moved a lot (don't ask), I added nuts to the locating studs. Problem is, now I have a big dis-assembly project to get at the lamp assembly. Don't know why I didn't replace the lamp when I had it all apart...

    --Greg

  5. #85

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    Quote Originally Posted by mdm View Post
    Any yellow stain?
    mdm's question is in regards to use of diazidostilbene sodium sulfonate.

    The answer is yes and no. And that it seems to depend on the paper used for final support.

    The sensitizer itself in solution is nearly clear, and does not seem to have an intrinsic stain, like the diazo sensitizers that have been discussed earlier in this thread.

    On my first test, I used a microporous inkjet paper, which i use sometimes for quick-and-dirty tests, to avoid using up my fixed-out photo paper. It has a tendency to show stain readily (even with dichromate and cyanotype), and it did. There was a significant brown stain that appeared within 2 hours of development and drying.

    The second test was on fixed-out FB paper, and it only started to show very faint stain about 12 hours after drying.

    Both were cleared about 36 hours after drying, using the formula posted earlier in this thread and in the UltraStable thread. Both cleared readily, without the frilling and emulsion damage that mdm reported in his tests.

    Can anyone reading this thread explain the chemistry of clearing these prints, especially the role of the potassium permanganate? For reference, the formula can be found here.

    --Greg

  6. #86
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    Quote Originally Posted by gmikol View Post
    Can anyone reading this thread explain the chemistry of clearing these prints, especially the role of the potassium permanganate? For reference, the formula can be found here.

    --Greg
    +1

    ----------------

    Inkjet papers contain dye mordants much like dye-transfer paper, which is what I transferred a q&d Ultrastable test to. Like your experience, a brown stain appeared in the next couple hours.

    I have seen these compounds (diazo/azido) referred to as dyes before.

    If your fixed-out FB paper was treated in a hardening fixer containing chrome alum or the like, you could expect this to have a mordanting effect as well, though significantly lower. It therefore might be interesting to observe what happens with photo-paper that was fixed out in a non-hardening fixer.
    If you are the big tree, we are the small axe

  7. #87
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    Greg;

    The Potassium Permanganate is a powerful oxidant which is probably there to destroy all of the residual organic chemicals in the coating. The second solution contains Sulfite which is probably there to scavenge any remaining Permanganate.

    PE

  8. #88

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    Thanks, PE, I suspected as much, but it's nice to have a little confirmation.

    This brings up another question, though, and not just directed at PE.

    It seems like we're transfering all of the health and environmental handling concerns from the dichromate to the permanganate. If one of the goals is to come up with a carbon process with fewer potential risks to human health and the environment, it seems like an alternative clearing solution should also be investigated. Would a strong hydrogen peroxide solution (say, 10%) serve a similar role?

    --Greg

  9. #89

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    Quote Originally Posted by holmburgers View Post
    If your fixed-out FB paper was treated in a hardening fixer...[snip]...It therefore might be interesting to observe what happens with photo-paper that was fixed out in a non-hardening fixer.
    The paper I used was fixed-out in a non-hardening fixer (Ilford Rapid Fix). The stain that developed was very faint (but noticeable) compared to your example and my first test, and took much longer to form.

    --Greg

  10. #90
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    Quote Originally Posted by gmikol View Post
    It seems like we're transfering all of the health and environmental handling concerns from the dichromate to the permanganate.
    That's a very good point, but if you look at the clearing formula A, it is a 0.6% solution of potassium permanganate which is then diluted 1:20 for use.

    If we assume we're using a tray and a big print, requiring 1 liter lets say, thats only 0.3225 grams of K-permanganate, whereas a K-dichromate tray sensitizer could require as much as 50 grams.
    If you are the big tree, we are the small axe



 

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