Last night in a conversation with a weaver friend I learned a little bit about metallic and tannic mordents and their associated tonal interaction with various natural dyes.... particularly earth oxides... (we are actually going to Iron Mine Bay this afternoon to a ‘secret’ place to collect a ‘special’ red dirt that I may find ‘interesting’). This got me to wondering about the variations in color tone of Platinum and Palladium prints that are achieved through the classical and modern methods and the unusual serendipitous color tones that appear in my prints when using unconventional developers and emulsion additives.
Specifically what I am wondering about is what is actually causing the variation of color shifts in the process. My perhaps mistaken assumption has always been that the actual image forming compound that remains at the end of the process is pure pt/pd metal and that the tonal continuum was dependent on the proportions of the metals used in the sensitizer... pt/warm-pd/cool and that the tonality that I was seeing was an inherent property of the pure metals.
However, in Dr. Ware’s process variations in tonality are occurring through changes in the RH and I believe other printers are achieving tonal shifts through variations in developer temperatures and changes in paper sizing. How do these factors actually effect the visual tonality of a noble metal? Is what remains after the process something other than what I had assumed? Is there actually some iron or other complex compounds left in the image that are effecting a tonal shift?
I ask this because I have tried using organic sources for tannic/pyro developers with the process and have been getting some unusual colors and I am now wondering if the color shifts may be a result of the formation of iron tannate or some such substance and that the chemistry that is resulting in the color shifts may in fact be a partial dying interaction between the paper/emulsion/developer combination and not something articulated by the nobel metals in the final image.