In the dawn of photography, it was far from obvious which light-sensitive substance might lead to success in developing the new art-science. Sir John Herschel, one of its pioneers, wrote in 1839:
'...I was on the point of abandoning the use of silver in theSilver salts had shown great promise for recording photographic images at the hands of Herschel's colleague, Henry Talbot, the inventor of photography on paper; whilst in France, unknown to them, a different process for making exquisite silver images on metal plates had been invented by Nicéphore Niépce and Louis Daguerre. Both the Photogenic Drawing and the Daguerreotype, as these processes were named, had their limitations. Aware of this, Herschel investigated many light-sensitive materials as alternatives to silver salts, including compounds of other noble metals, dyestuffs extracted from flowers and, most significantly, the iron salts of certain organic acids which occur naturally in the plant kingdom.enquiry altogether and having recourse to Gold or Platina...'
In 1842, Herschel discovered that light transformed ferric ammonium citrate into the ferrous state, which could then be used to make permanent images by reduction of a noble metal salt to the inert metal. Thus, he made contact-prints in gold, silver, mercury, and the pigment Prussian blue, which he dubbed, respectively: chrysotype, argentotype, amphitype, and cyanotype. A later innovator, William Willis, found a similar way to print in platinum and palladium, giving us the platinotype and palladiotype.
None of these iron-based monochrome processes, however, proved sensitive enough for the camera. It turned out that Talbot had been on the right track; his invention of calotype set photography on the road to today's negative-positive process, in which the chemical development of a latent image in a silver halide emulsion achieves a photographic speed sufficient to capture the camera negative 'instantaneously'.
The printing of a positive photograph from a camera negative is more leisurely than negative-making, because lengthy exposures are no limitation, and light sources can be intense. So for this purpose the slow contact-printing processes devised by Herschel are brought back into play, and some were accepted into 19th Century photographic practice, when popular negative formats were much larger than today. But, early in the 20th Century, the evolution of miniature camera formats made image enlargement a necessity, calling for the more sensitive gelatin-silver halide development papers. Thus, a major manufacturing industry was founded, which soon dominated the commercial photographic market, forcing the iron-based processes into obsolescence. Ironically (!), the practice died out completely in its birthplace, Britain. But, in a counter-flow to the commercial stream, and driven by dissatisfaction with the increasingly limited range of surfaces and tones offered by the manufactured printing papers, a few dedicated artists in the USA re-discovered the iron-based processes and kept them alive in the intervening years by hand-coating their own papers.
As commerce withdraws its interest from photochemical image-making and re-invests in electronic media, the traditional practices of analogue photography will revert into the hands of those with whom it began - or rather, their spiritual heirs: the dedicated photographic artists, experimenters, and craftspeople. It is very hard to replicate the multi-layered, silver-gelatin printing papers manufactured by the industry, which may soon vanish altogether in the 21st century. Rather, to make permanent photographic images in the future, we may prefer to turn to the simple and beautiful alternative processes.
The chief difference between making an iron-based print and using the silver-gelatin product lies in the hand-crafted aspect. Alternative printers are rewarded for their labour (which is considerable!) by the satisfaction of being true to their materials. Hand-made plain-paper prints distinguish themselves from silver-gelatin by the absence of any binder layer. The image resides within the surface fibres of the sheet, and its matte surface acquires a tactile quality akin to an engraving or a water-colour. Connoisseurship can tell if a print is a good work of art, but can rarely say whether the print is also a good work of science. I believe that artists deserve the best science. To perfect these beautiful processes calls for a degree of scientific professionalism no less than that which has been devoted to the commercial photographic medium.
Subtle quality, total permanence, and ease of working place the platinotype at the summit of alternative photographic printing. Platinum and palladium can yield colours ranging from blue-black, through neutral greys, to rich sepia browns. The tonal separation in the middle values is excellent, and great delicacy can be achieved in the highlights, imparting a beguiling luminosity to the print. This medium has in recent years enjoyed a renaissance, especially in the USA, because it evidently meets an aesthetic need in some people's expressive work. In collaboration with Professor Pradip Malde in the mid-1980s, I developed a modern printing-out method of platino-palladiotype that is economic and reliable, enabling a consistency of working that had been difficult to achieve with traditional process.
The British photographic establishment has been reluctant to acknowledge cyanotype as a valid pictorial medium, thanks to the intolerant response of 19th century British critics to its powerful and uncompromising colour. Fortunately this prejudice did not prevail universally. In the USA, Canada, and France, there are substantial museum holdings of artistic cyanotypes. Herschel's original cyanotype formula has survived essentially unchanged for 160 years, due to its pleasing simplicity and economy; but I found it possible in 1994 to make some small improvements in the chemistry which confer greater speed, stability, convenience and quality on the process.