Thursday, March 31, 2005 at 5:30 pm in the Elvehjem
The decorative uses of that most alluring metal, gold, go back into human prehistory, but knowledge of the metal in its colloidal state dates only from the mid-17th century, when it was first employed as the purple of Cassius for staining glass and ceramics to a fine deep red. This superb pigment has now joined the very select group of noble metals - silver, platinum and palladium - that can be used as image substances for monochrome photographs.
In 1842 Sir John Herschel coined the name chrysotype to describe his invention of photographic printing in pure gold. But by then, silver printing was rapidly improving at the hands of his colleague, Henry Talbot, so Herschel's embryonic gold process was never brought to fruition, owing to its higher cost and inherent chemical problems. Eclipsed by silver prints since the beginning, the elusive chrysotype process has resisted every attempt to tame it. Probably the only historical specimens of chrysotype to come down to us are those made by Herschel himself, now in the collections of the Museum of the History of Science, Oxford, the Royal Society, London, and the Harry Ransom Humanities Research Center, University of Texas at Austin.
Chrysotype resembles the better-known, and at one time widely-practised, platinotype process of William Willis, but there are clear chemical reasons why it is intrinsically more difficult to use salts of gold, rather than platinum, in an iron-based photographic sensitizer. Indeed, the recognition of these difficulties by the leading technical authorities on photography in the past has led them all to discount the feasibility of gold printing. Although the notion has been in the air since the earliest days of photography, it has never before been carried into successful practice. A controllable gold-printing process is only made possible with the aid of some modern chemistry, whereby the vigorously oxidising nature of the gold salts can be moderated. As the culmination of ten years research, Dr. Mike Ware - a chemist, photohistorian, and exhibiting photographer- has perfected formulae for iron-based gold-printing sensitizers. His new chrysotype process is probably the first chemically novel method of precious metal printing to be devised for over a century.
The use of gold confers great longevity on the images: chrysotypes are extremely light-fast and resistant to chemical attack; they enjoy an archival permanence excelling even that of platinotypes because, unlike platinum, gold has little catalytic activity, so does not assist the acidic embrittlement of the paper base which is the besetting disease of historic platinotypes. Colloidal, or nanoparticle gold also has the advantage of a very high covering power, which makes use of the medium significantly less profligate than platinotype. Chrysotype shares with this handcrafted process the same characteristics of a perfectly matte print surface and subtle tonal gradation, but differs from platinotype in one other important respect: besides the fine neutral monochrome tones, chrysotypes can also be made to display a wide range of colour; including pink, magenta, brown, purple, violet, blue or green. This enhancement provides the creative photographer with an extra dimension to explore, in which the colour of a print may be matched to the expressive intent of the picture. It is remarkable that, despite their various hues, the images still consist of nothing but pure gold; the colours are due to the different sizes and shapes of the gold nanoparticles determining the various wavelengths of light which are absorbed and scattered. The particle size is, in turn, controlled by the chemistry of the sensitizer and the conditions of processing, so the photographic artist has full control of this new palette of colour.
Mike Ware will be one of four artists whose works will be displayed in The Color of Iron, a special exhibit scheduled for November 19th, 2005 through January 22nd, 2006 in the Mayer Gallery of the Chazen Museum of Art, on the University of Wisconsin-Madison campus.