The monochrome prints are only available as Platinum Palladium Prints. This printing process was first patented by William Wallis in 1873. It's widely regarded as the finest photographic printing process available. A properly processed Platinum Palladium print can in theory last forever, and although some estimates suggest they can last a thousand years that claim is obviously difficult to prove. Certainly a Platinum Palladium print will last as long as the paper it's printed on. Some fine Japanese papers have been proven to last a thousand years, and that is why some of my prints are produced on the wonderful Japanese Tosa Washi and Kouzo papers.
A finished Platinum Palladium Print is a thing of rare beauty. A good print is capable of showing twice as many tones as a normal Silver Gelatine Print, with very subtle rendering of the high tones that cannot be matched by any other method. The image of a Platinum Palladium Print is embedded into the surface fibres of the paper and is pure Platinum and Palladium metal, this is why it has such an extreme archival life. What you have as a result is a print that consists solely of the most commonest organic molecule in the World, cellulose, and the most stable of metals known, Platinum and Palladium.
I use a mixture of Platinum and Palladium to enable a range of varying negatives to be printed with predictable results. By mixing the Platinum and Palladium metal salts in various ratios I can control the smoothness, contrast and colour of the final print. This combination is further mixed with light sensitive ferric oxalate salts which converts the Platinum Palladium solution to pure metal upon exposure to strong UV light and development. Humidity and temperature of the paper at the time of coating and development also influences the outcome of the print, I often use a humidification chamber to attain a certain level of humidity for the paper before coating and exposure. Also the temperature of the potassium oxalate developer affects the final tone of the print. A warm developer gives me an almost sepia look. I work surrounded by hygrometers and thermometers, constantly making notes of their readings.
Each print is hand made and therefore unique. Firstly the paper is coated with a Platinum and Palladium emulsion and left to dry for a couple of hours, then an enlarged negative is sandwiched with a sheet of paper and exposed in a UV vacuum press. The exposed paper is developed in a bath of potassium oxalate chemical to intensify the image. After clearing and fixing the paper it is air dried. Quite often to increase the maximum density of the image, the paper is coated and re-exposed up to three times until the desired quality is reached.
Selection of paper is very important to get a good Platinum print. My normal material is a pure unsized 320 gram cotton rag paper. Quite often I use Japanese Gampi and Kouzo tissue paper which give the most beautiful luminous and diaphanous prints. Unfortunately these papers are very difficult to work with, although the results are always worth the effort.
I have heard that some Platinum printers, who have been working with the process for over 30 years, are still striving for the perfect print. I know how they feel because I am often disappointed at the result of a print, but after about the tenth attempt and by tweaking the settings and chemicals I often get a print I am happy with. There's nothing quite like that moment when you look at a finished print knowing that it finally represents the feeling you experienced when you made the image in the first place.