Hi Bob, good to hear your testing is going well, carbon over palladium sounds interesting. Good luck with that and look forward to seeing the results.
Originally Posted by Bob Carnie
Speaking to others gelatin seems to be a problem for prints with platinum in however palladium works well.
You might be interested in these transcripts of the notes Penn wrote on Platinum printing that are available from the Archives of the Art Institute of Chicago. Some of them are shown below.
'PH of paper greatest importance. Gray stain when even acid paper used without addition of HCL when coating. Bad stain when neutral or alkaline paper (Fabriano, unsized) used. Addition of 1.5 drops per cc of metallic solution required to reduce stain to acceptable level. (Some formulas use oxalic acid in fairly large amount in coating solution. I must explore this more fully.)
Kurt Steirs research (see his notes) indicates paper lasting quality almost entirely dependent on PH of paper. An acid condition is destructive. In our work this acidity is apparently cumulative. An acid paper (W.T.) + acidic result of alum size + hydrochloric acid of process leaves a PH that must be altered by additional chemical baths. (see K.S. notes).
Since we find that W.T. paper is not sufficiently neutral to face our finished prints, we have found from Andrews-Nelson-Whitehead a paper (tissue) used by the Smithsonian and the Library of Congress. Our tests indicate a PH of ________. Mrs. Vera Freeman A-N-W paper Co.
There is a serious difference in the behavior of platinum and palladium as a coating medium. Literature to the contrary is nonsense.
Palladium is softer and tends to have softer edges to the grain. It continues to bleach for hours in HCL. The result is an image with something of the quality of a stain. It tends to the brownish and faded look of an old silver-print. Any unevenness is in the original sizing of the paper is multiplied many times in the bleaching process. Our tests indicate that the dry image is absolutely fast to light.) It is difficult to decide on an exposure since one might attempt to prevision the final result of hours later.
Platinum is harder and clearer than palladium. The grain is more apparent than even in the negative from which the print is made. (There is a limit apparently to the softness one can get on platinum.) However the image as it appears in the developer is exactly what will be there even hours of HCL later! This is a joy. (The image of platinum is much slower coming up than palladium. Id guess 3 mins as against 30 seconds to more or less completion of development). Using platinum as the underprinting gives one the chance to abandon the plate early in the game if it seems that the highlights are too dark or too light, since the image is unalterable by further time or manipulation.
Use of iridium with palladium. Is this basically a toning of the palladium image? Great cost is a discouraging factor in its use.
Because of the time consumed in constant experimentation it is necessary to ration oneself and keep the objective of making fine prints foremost. This leaves many technical questions unanswered.
Our whole use of the platinum process for print-making was conditioned by the existence of modern materials, (estar base films, aluminum sheets, surelyn) which enrich the possibilities of hand-coated platinum (palladium, iridium).
The separation of the enlarged negative image into the basic negative + a highlight mask + 1 or 2 overprintings for the shadows gives enormous scope to the printing possibilities. The image is in effect reassembled in an altered relationship of the components.
The Xenon light makes possible a consistent exposure of a consistent color temperature night and day. We have used it always with a paper test strip. The light is actually on a trolley which allows alteration of distance marked on a tape-measure on the floor.
The further the light source is from the printing frame, the nearer it approaches a point source but the time increases in geometric proportion. From a practice time point of view we tend to use 2 1/2 ft for the 4000 Xenon and 36 for the 8000 Xenon. A large fan blows on the printing frame glass during the entire exposure and an exhaust fan removes the heat that builds up rapidly in the exposing room.
There is a die supplied by Condit who made our strips. A punch is used to make the screw holes that eventually hold the registration strip. Indentations were ground into the printing frame glass to accommodate the raised studs of the registration strip and insure absolute flat contact of the elements enclosed in the frame during exposure.'
Last edited by Davec101; 09-07-2012 at 05:22 AM. Click to view previous post history.