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By Mike Ware on

The New Chrysotype Process

The New Chrysotype Process is so named in honour of Sir John Herschel who, in his classic paper of 1842 (1), first coined the term chrysotype to describe the photochemical production of an image in colloidal gold metal.

However, this embryonic process was never accepted into the repertoire of photographic printing, owing to inherent problems of fogging, excessive contrast and uncontrollable colours. A few sporadic reports have appeared in the literature describing attempts by photographers to take up the process—in 1859 (2) and 1911 (3,4)—but today the only known surviving specimens of historic chrysotype prints are about 22 originals by Herschel himself, distributed between archives in Oxford, London and Texas.

Chrysotype is an iron-based printing (“siderotype”) process resembling the more familiar and at one time widely-practised platinotype process; but it is intrinsically more difficult to use gold salts than the analogous platinum or palladium compounds. Indeed, it was the recognition of the chemical difficulties that led both Pizzighelli and Hbl (5) and Abney and Clark (6), in their well-known treatises on platinotype, to discount the feasibility of gold printing. Thus, although the notion of gold printing has been ‘in the air’ since the first days of photography and gold has found several photographic uses (7) (notably as a toning agent for silver prints), it is only with the aid of modern chemistry that the vigorously oxidising nature of the gold salts can be moderated, and a controllable gold printing process developed. The New Chrysotype Process is probably the first chemically novel method of iron based printing to be invented since the end of the nineteenth century (8).

In 1989, as the culmination of six years research, Dr Mike Ware—then lecturer in chemistry at the University of Manchester and an exhibiting photographer—perfected formulae for iron-based gold printing sensitizers which are now fully published (9). The chrysotypes can be obtained in a wide range of colours including pink, magenta, brown, purple, violet, blue or green, even though the images contain nothing except pure gold. It is a remarkable fact that these colours are due solely to variations in the size and shape of the submicroscopic gold nanoparticles interacting differently with light, according to Mie’s scattering theory (10). The particle size of the colloid is in turn controlled by the chemistry of the sensitizer and the conditions of processing. Nanoparticle gold also has a very high photometric equivalent (‘covering power’), making the medium significantly less expensive than platinum printing (11).

Gold images have been shown to be very light-fast and resistant to chemical attack; they therefore enjoy an archival permanence equal to the platinotype, and share with this hand coated process the same characteristics of matt, textured surface and subtle tonal gradation, but with the added enhancement of colour. It is hoped that this extension of monochrome image-making may provide print-makers with a new dimension to explore in matching the colours of their prints to the expressive intent of their images.


Sources

  1. Sir John Herschel, Philosophical Transactions of the Royal Society, 181 (1842)
  2. The Duke de Luynes, The Photographic News, 3:258 (1860)
  3. A J Jarman, Amateur Photographer, 5:722 (1911)
  4. Chapman Jones, The Photographic Journal, 51:159 (1911)
  5. G Pizzighelli and A Hbl, Platinotype, (London: Harrison and Son, 1886)
  6. Sir W de W Abney and Lyonel Clark, Platinotype, (1895)
  7. P Ellis, The Gold Bulletin, 8:1 (1975) p.7
  8. Mike Ware, ‘Herschel’s Chrysotype: A Golden Legend Re-told’, History of Photography, 30:1 (Spring 2006) p.1-24
  9. Mike Ware,’Chrysotype: Photography in Nanoparticle Gold’, Gold Bulletin, 39:3, p.124-131; The Chrysotype Manual: The Science and Practice of Photographic Printing in Gold, (Brighton: ffotoffilm publishing, 2006); Gold in Photography: The History and Art of Chrysotype, (Brighton: ffotoffilm publishing, 2006)
  10. G Mie, Annalen der Physik, 25:377 (1908)
  11. M J Ware, The Journal of Photographic Science, 34:13 (1986)

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