Re: Two carbon questions

Re: Two carbon questionsSandy,

I already have figure out some aspect (theorical) of the pigment concentration, the tickness of the coating (emulsion) in relation to Dmax, this without taking into account (yet) of what you have very well describe with "the height of the tissue needs to be affected by UV exposure". Obviously, taking exposure and the amount of dichromate into consideration will all affect the end result, ultimately the Dmax, the depth of relief and the oveall response of my (our) carbon prints will be affected by the interrelations of all those variables. You already know all this either intuitively because of your experience with the medium or by methodic testing or whatever, in other words you are probably your own and most severe critic and you know what your doing.

The problem I have is time and my nature. I'll never show a print I've made until I'm convinced I can't do better. The time it took you to be satistied of your work, you can multiply this by at least two in my case if I go at it without a clear an rigorous approach. I need a protocole or a methodology which will allow me to learn an in depth knowledge about the innerworks of carbon printing and it will take me nothing less to acquire this confidence and all this in a reasonable amount of time. I think I have a good example of what I'm thinking of and where you can find it, on the Kodak website they have made available what I call the datasheet for films, I have the TMax 400 in mind but most others would do just as well. With these few sheets you can have a pretty good idea of what to expect from your film and what to do to get it but still I'm sure someone like you can add a few more sheets to these. I'm convinced though, I don't need to explore all the range of possibilities of carbon printing before I can consider my prints as "fine prints" whatever that can mean. I just know that when I'll know, I'll know.

Thanks for sharing your knowledge with us.
Yves

  ----- Original Message -----
  From: Sandy King
  To: alt-photo-process-l@usask.ca
  Sent: Thursday, April 13, 2006 11:27 AM
  Subject: Re: Two carbon questions

    The amount Sandy suggested seems to be about twice as much as my extrapolated value which could mean 5% increase may be far from enough. If I recall correctly Sandy as plenty of experience and I would be confident starting with his numbers instead of mine (guesstimates).

    Regards
    Yves

  Yves,

  I would emphasize that the exact amount of pigment needed is only critical when the goal is to make tissues that give very high relief prints. If the goal is to just make carbon prints that have very good Dmax a considerable excess of pigment does no harm -- you just compensate for it by adjusting the strength of the dichromate sensitizer to the contrast of your negative. In development you would find that a tissue of this type would retain a very large amount of pigmented gelatin when you strip it from the final paper support.

  However, if prints of high relief are desired one must adjust the amount of pigment to the minimum. The coating must be completely opaque, but most of the height of the tissue needs to be affected by UV exposure. In development you would find that a tissue of this type would retain very, very little pigmented gelatin when you strip it from the final paper support.

  Sandy
Received on Thu Apr 13 12:07:26 2006