Dick Arentz in his Pt/Pd printing manual seems to imply that this relative
lack of sharpness is inherent to hand coating.
David Fokos (beakman@netcom.com) told me:
>This has nothing to do with the
>emulsions - it's a function of the paper. The smoother and glossier the
>paper, and the less the emulsion soaks in, the greater the sharpness will
>be. Since platinum emulsion won't adhere to a paper as hard and glossy
>as regular photo paper, we use watercolor papers which obviously do not
>have any gloss, and they are a bit less smooth - resulting in a bit less
>sharpness when compared with regular silver-based papers.
I am interested to know thoughts of Pt/Pd printers on this partly because I
am thinking of experimenting with alternative methods of coating.
The following quotes might be relevant to a discussion of sharpness and
granularity of a Pt/Pd print.
>Mike Ware <mike@mikeware.demon.co.uk> said:
>I believe this
>is governed chiefly by the geometry of the light source, but closeness of
>contact between negative and sensitized layer and the depth to which the
>sensitizer has penetrated the paper could also be important
>The issue of 'graininess'
>or granularity in a Pt/Pd print. I believe this commonly appears when the
>development chemistry is too 'slow' - i.e. the exposed sensitizer chemicals
>are partially washed out of the paper before the precipitation of noble
>metal is complete. The result is an image concentrated in the less
>accessible regions of the paper fibres, leaving a fibrous or granular look.
>The remedies are: more vigorous developers, hot developers, and the
>avoidance of any substance that inhibits the platinum chemistry (e.g.
>gelatin).
>Our print-out method does not suffer from this problem because the image is
>substantially complete before immersion in the wet clearing baths.
Pradip Malde (pmalde@seraph1.sewanee.edu) said:
>The greatest culprit here is the use
>of so-called contrast control additives like potassium chlorate. It is
>these additives that increase grain and truncate the highlite values. There
>is a better way to control contrast - see my article in View Camera. ALSO -
>the potassium based system generally is more grainy than the new system
>which I describe in the aforementioned article... check it out.
______________________________
Edgar Y. Choueiri
choueiri@princeton.edu