Increasing Azo Contrast

Discussion in 'Contact Printing' started by David Hall, Mar 7, 2003.

  1. David Hall

    David Hall Member

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    For those of use who use Azo in Amidol, we know that using a water bath will decrease contrast up to a whole grade.

    But what if I need to increase it? The highest grade paper I have is 3, and I have a negative that is still flat on that. Is there an exposure or chemical way to take the grade 3 paper toward 4? Using Amidol?

    dgh
     
  2. Jorge

    Jorge Inactive

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    David, I have never tried this and dont know if it will work, but if you can decrease contrast by "bleaching" the latent image with ferrycyanide before you develop, perhaps you can increase it by "toning" the latent image before you develop. Why dont you try selenium toner maybe 1:500 and put the print in the bath before you develop it. Rinse it and then develop it in amidol, and see what happens, and let me know if it worked.
     
  3. Donald Miller

    Donald Miller Member

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    David,

    If what Jorge suggested does not work (it may very well do so), the things that I would try would be:

    1.intensify your negative with selenium toner. Since selenium is proportional to silver density it will increase negative contrast. I have used selenium in dilutions of 1 to 3 for this purpose.

    2. If that doesn't produce enough contrast the next step would be to create a low density unsharp negative mask of your camera negative. This mask would be printed along with your camera negative. The mask will give you an unlimited amount of contrast increase depending on the density of the mask.

    Good luck.
    Donald Miller
     
  4. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    In general I find I need one zone more contrast with Azo than I do with most grade 2 enlarging papers.

    Selenium intensification of the neg will give you about a one-zone boost. I'd try that first. I also use 1:3 for this purpose.

    Another thing you might try is printing down the whole image then bleaching it back to the highlight values you're after.
     
  5. David Hall

    David Hall Member

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    Donald and David,

    I have always been interested in intensifying a negative but never did it because I don't understand the chemistry of it enough...if I intensify it by one full stop, do I either blow highlights or erase shadow detail in the process?

    dgh
     
  6. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Selenium intensification adds density proportionally to the negative. If the negative is flat and you want up to one zone of expansion, you won't blow the highlights, but you will bring them up one zone. If the negative already has sufficient contrast, then you would blow the highlights by bringing them up one zone, but why would you intensify a negative that is already sufficiently intense? You won't lose shadow detail at all. Rather, you'll increase it.
     
  7. David Hall

    David Hall Member

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    Great. I will try the intensification tonight. Anything I need to know other than selenium 1:3? Do I need to constantly agitate to avoid streaking or blotching? Is it easy to see it happening, or do I measure it by time?

    dgh
     
  8. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    I would agitate constantly in a tray, but I've never had streaking problems. You can see it happening if you use a white tray and have good light, but for reference, I usually go about 8 minutes in Kodak RST 1:3, 68 deg. for thoroughly washed negs (re-wet them first, if they are dry) that have been fixed in an acid fixer. I haven't timed it precisely for negs fixed in TF-4, but it's probably shorter.
     
  9. Donald Miller

    Donald Miller Member

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    David,

    I don't think that you can leave a negative in the selenium too long, within reason. It will reach a point of maximum effect and nothing happens after that. The selenium actually would have the same effect on the silver density of the negative that it does on paper. It would tend to make the negative image more archival since the same chemical change occurs.
     
  10. David Hall

    David Hall Member

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    Thanks!

    And, Donald, to answer your signature line...

    "whoosh. Whoosh. Whoosh."

    dgh
     
  11. Donald Miller

    Donald Miller Member

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    David, Think so, huh????
     
  12. c6h6o3

    c6h6o3 Member

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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (David A. Goldfarb @ Mar 7 2003, 11:53 AM)</td></tr><tr><td id='QUOTE'>If the negative is flat and you want up to one zone of expansion, you won't blow the highlights, but you will bring them up one zone</td></tr></table><span class='postcolor'>
    How does it affect pyro stain?
     
  13. Les McLean

    Les McLean Subscriber

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    I've never used Azo or Amidol but when faced with a flat negative that needs more contrast than I can get with the hardest paper grade available I resort to underexposure and overdevelopment just as I would do when looking to increase the contrast when developing film.

    The procedure is as follows. Make the best possible print even though you know it needs more contrast. Make a second print but reduce the exposure by 30 to 50% and process in the same developer used for the first print. You will have to develop by inspection which could take up to 40 minutes, that's the longest I've developed in these circumstances. I process in the dark, switching on the safelight occasionally to check the progress. Clearly there is a large degree of trial and error involved but it does work with both graded and VC papers. Don't be afraid to go to the extremes to get a result.
     
  14. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    c6h6o3: I haven't tried it yet with a pyro neg. Usually I've used it with TMX, which I develop in D-76 (1+1), and which tends not to have enough density range for Azo, but I have read that it works with pyro negs. The effect is actually similar to pyro, since both add density proportionally to the highlights, though selenium intensification doesn't produce the edge effects, etc. of pyro. Try it with a neg that is otherwise a reject and report back!
     
  15. Ole

    Ole Moderator Staff Member Moderator

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    C6H6O3? Would that be the pyrogallol formula, by any chance?


    What about using a higher-contrast paper developer? I can understand why people want to use Amidol (although I can't - no local sources), but even with Amidol it should be possible to make a high-contrast formula?
     
  16. Tom Perkins

    Tom Perkins Member

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    It may be worth a try to take it from the amidol to a second bath with full strength Dektol for about half or a quarter of the devloping time. Sometimes it will set the contrast. Good luck. Tom Perkins
     
  17. Tom Duffy

    Tom Duffy Member

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    Concerning the effect of selenium toning on a pryo neg, I was once told by the tech support guy at Bostick and Sullivan that this would intensify the negative but "eliminate" the pyro stain. "Eliminate" is my word, I don't remember his exact word. I often thought about trying the technique on an unevenly stained pyro neg to see if I could fix it.
     
  18. edbuffaloe

    edbuffaloe Member

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    You might try Fein's Amidol formula--it is very contrasty and gives very clean high values due the quantity of anti-foggant and citric acid. However, it typically gives a rather blue-black image color.
     
  19. David Hall

    David Hall Member

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    Thanks Ed.

    And, while you are here, I remember reading in your Smith-Amidol article that you tone prints in selenium at a much different dilution than he does. Did you try it his way and find that it didn't work for you or that your lower dilition works better or faster? In other words, why the difference?

    dgh
     
  20. edbuffaloe

    edbuffaloe Member

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    I keep a bottle of selenium toner in a standard dilution of 1:15, so that is what I used. I pulled the print when it reached the tone I liked. I would be willing to bet the 1:15 works a lot faster than the 1:128, though I'm not saying it is better or worse--just that it works for me.
     
  21. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    If you use an acid fixer, Azo will reach Dmax in KRST 1+15 in about 3 minutes, I find, and in 4 minutes it will go purple brown. If you use TF-4, you'll reach Dmax in about 45 seconds in 1+15.
     
  22. David Hall

    David Hall Member

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    Great info! David, does Dmax include losing the green cast of the Azo? And you're talking Amidol development, right? Does it matter?

    dgh
     
  23. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Selenium does correct a green cast if you're getting one. I've been developing in Agfa Neutol WA, but will start experimenting with Amidol soon. I don't find that Azo has a green cast with Neutol WA, though it does slightly with Dektol.

    Be sure to time your toning with Azo in selenium, though, and until you are sure of how it works with your particular combination, make sure you have some spare prints in case you go too far. When you cross the line from max black to purple-brown it's very sudden and irreversible. The purple-brown is actually kind of nice for certain images, and you can vary the extent of it with careful timing.
     
  24. jmcd

    jmcd Member

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    Another possible solution to increase contrast with Azo and Agfa WA: yesterday I was printing a negative in WA 1:7, and the print was sharp and overall scene contrast about right, but murky flat in the darker tones. The negative was HP5+, and the scene was recorded in flat light. I made a tray of WA 1:4, and this increased the snappiness of the print to where I felt good about it.