Carbon printing and Nuarc

Discussion in 'Alternative Processes' started by Jorge, Jul 28, 2005.

  1. Jorge

    Jorge Inactive

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    Ok, I am ready to start doing some printing tests with step wedges to determine best exposure and contrast, is anybody here using Nuarc platemakers to expose carbon and if so what is your base exposure? I just need a ball park figure. I dont want to overexpose as that would harden all the gelatin.
     
  2. sanking

    sanking Member

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    Depends a lot on your tissue and how it was made. If you are using B&S tissue, exposures should be in the 2-4 minute range for in-camera negatives that are well (but not over-) exposed.

    The 2-4 minutes refers of course to time after the lamp reachs full intensity. If you have the integrator timed to where one second equals oine unit try exposures in the 120-250 units.

    Sandy
     
  3. Jorge

    Jorge Inactive

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    Thanks, that should be about 150 units, is this what you are using?
     
  4. sanking

    sanking Member

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    Yes, my exposures with the NuArc run from about 125-200 units.

    How are you sensitizing?

    Sandy
     
  5. Jorge

    Jorge Inactive

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    I am planing to start exposure testing with potassium dichromate at 1, 2, 3, and 4 % 1.5 minutes in a mixture of water and alcohol solvent. I figure it will dry faster this way than with just water.
     
  6. mikewhi

    mikewhi Member

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    Excuse me, guys, but this is an English Only Forum, ok? I'm not sure what language you're speaking, but please post to the appropriate forums.

    Gracias.

    -Mike
     
  7. Jorge

    Jorge Inactive

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    Hey Mike, we are using alternative language for alternative printing.... :D
     
  8. sanking

    sanking Member

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    Yes, it will dry faster this way, and I believe this is how Dick Sullivan recommends sensitizing. Or something similars to this.

    However, I just use plain water and squeegee out the excess dichromate on clean plastic or glass (emulsion side down) and the tissue (on plastic base) dries very fast anyway, within less than 30 minutes in my climate. Since you live in an area where I would guess the RH is pretty low I would suggest that the addition of alcohol might just be an added complication.

    Sandy
     
  9. Jorge

    Jorge Inactive

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    If it dries too fast then it curls too much, or is there another reason for slower drying? How "hard" should I squeegee? I would prefer not to use alcohol, so if you think I will be alright without it, I will try it your way.
     
  10. sanking

    sanking Member

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    Squeegee lightly, then place on a drying rack and accelerate drying with a small fan on low at about 3-4 feet from the tissue.

    Not sure which tissue you have, but Dick recently changed bases. The old base was about 3 or 4 mil thick and for some reason you had to limit time in the sensitizer to about one minute or the tissue would frill off at the edges. The new base is about 6 or 7 mil thick and can stand sensitizing times up to three minutes, maybe more but more than three minute is not necessary.

    Be very careful with valuable negatives since they will stick to the tissue if it is not absolutely dry, and sometimes it is difficult to tell that it is absolutely dry in every spot. Best practice is to use thin Mylar between the tissue and sensitized tissue.

    Sandy
     
  11. Jorge

    Jorge Inactive

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    Once again thanks, it looks like I got the thin back since it frilled at the edges with a 1.5 sec sensitizing. No big deal I left enough to extra space for this not to matter.....
     
  12. magic823

    magic823 Member

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    Good to know since I'll be using my Nuarc soon (just as soon as my sink plumbing gets put in.) Again Sandy, thanks for all the help.

    Steve