From: Jean-Paul Gandolfo (jpgalt@infonie.fr)
Date: 10/17/01-02:59:04 AM Z
In a message dated october 16 th, Katharine wrote :
> just by adjusting pigment concentration, dichromate concentration, and
> exposure, any degree of contrast desired can be attained, whatever the
> light source.
About light parameter in pigmented processes the dichromated coating acts
as a strong yellow filter with an absorbing band very effective in the UV
area of the spectra. I haven't the pratice of gum printing, only carbon
printing but I think the problematics are similar. With carbon printing,
without changing your tissue formula, you can have a "multigrad paper" by
printing with various light systems (gas discharg, tungsten, direct sky,
shadow sky light ...). A light source UV rich and visible poor, as black
light, gives a "low deep" (superficial) print, even with a thick coating.
Hope this help
-- Jean-Paul GANDOLFO French National School of Photography Louis LUMIERE BP 22 93161 Noisy le Grand cedexTel : 01 48 15 40 20 e-mail : jpgalt@infonie.fr
----------
This archive was generated by hypermail 2b30 : 11/02/01-08:55:27 AM Z CST