First and foremost, this process is available today thanks to Pradip Malde and Mike Ware. Full acknowledgments to them.
What is the POP Platinum Palladium or The Ammonium Print Out Method? To begin with, it’s not a develop-out process (DOP). The traditional Platinum Palladium printing process uses a developer, like Potassium Oxalate, to develop the picture. Like Albumen, Salt, Collodio-Chloride, etcetera, the Print-Out Platinum Palladium, or The Ammonium Print Out method uses the sun (or UV light) to develop the picture.
This is from Pradip’s website, “In recent years platinum-palladium printing has regained its place at the summit of alternative photographic practice, renowned for the subtly nuanced tonal qualities of its images, formed by totally permanent ‘noble’ metals in the matte surface of artists’ paper. Willis’s traditional platinotype and palladiotype were development processes, and capable of beautiful results in skilled hands, but they suffered from some chemical inconsistencies. The method described here employs a better-behaved iron sensitizer, derived from the ‘print-out’ platinum process due to Giuseppe Pizzighelli in 1887. Read Mike Ware’s technical comparison of the modernized version with the earlier processes.
This modernized version has some advantages in economy, accessible chemistry, and exposure control. Using the procedures described in these notes, platinum or palladium may be used individually or mixed in any proportion, providing a choice of the image hue between neutral grey-black and rich sepia. A controlled degree of humidity is allowed in the sensitized paper to promote the formation of a printed-out image in platinum/palladium during the exposure, requiring little or no development. A carefully-devised clearing sequence ensures that all the iron is removed from the paper.”
Mike Ware wrote a technical comparison. Here’s an excerpt from the writing, “Thus a ‘print-out’ process results, in which the final image is formed substantially during the light exposure, and no ‘development’ bath is required, simply ‘clearing’ baths to remove the excess soluble chemicals. This enables a modus operandi quite different from the traditional method, and more economical in time, effort, and materials. Images may be printed satisfactorily ‘by inspection’, without prior calibration. The print-out process is ‘self-masking’, in that the blackening of the shadow tones inhibits their further darkening by light, so a long density range in the negative may be accommodated, and the control of contrast is more relaxed. By regulating the relative humidity of the paper before exposure, better image colors result with palladium, because the metal nanoparticles are allowed to grow larger, and can furnish even a neutral black. Provided that a suitable paper substrate is chosen, the method can also yield an excellent print in pure platinum.
In conclusion, it might be observed that, for many artists, the intrusion of technical minutiae into the creative workflow can tend to inhibit their endeavors. If the science can be predesigned to work as transparently and unobtrusively as possible, so much the better for art. Artists deserve the best science.”
Another book I would recommend if you don’t have it is “Coming Into Focus” by John Barnier. Both are excellent for information on semi-obscure historic processes.
