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Herschel's Phytotypes (Vegetable Photographs)

Herschel's Phytotypes (Vegetable Photographs)

The most extraordinary and improbable extension of Sir John Herschel's wide exploration of photo-sensitive materials was the use of juices extracted from flower petals. These 'vegetable photographs' extended photography beyond the usual metallic salts and other chemicals of the laboratory. One of the things Herschel was interested in, beyond the exploration of alternative light-sensitive agents, was colour. Although the nature of the photographic process doomed the invention to being monochrome, the early experimenters, as their products show, had no preconceived notion that this must be 'black-and-white', or even the sepia that became dominant. Talbot's photogenic drawings displayed a wide range of colours; Hunt's process produced a beautiful yellow or greenish image (34450, 62706) and even in 1839 Herschel had found a range of striking colours without going beyond the silver-based image and familiar chemical compounds. In 1842 he built on these beginnings to invent the iron-based cyanotype (blue) and chrysotype (purple).

Meanwhile, in 1841-42, he explored the softer and more delicate colours derived from plants. It was a die/bleach process, operating in the opposite way to the darkening of silver salts. The extract dyed the paper, and exposure to light then bleached it. The result was, as in Hunt's process, a direct positive image. The colours achieved however were not necessarily those expected from the source. Crimson poppy - one of the most successful - produced an image that was a slate blue-grey. The results fascinated Herschel and many of his contemporaries, and were of great scientific originality; but although he published the details in the Royal Society's Philosophical Transactions he concluded it would not be a viable photographic process. Not only was it extremely slow, but the resulting image could not be preserved from further change. Existing fixatives such as hypo were chemicals that neutralised light-sensitive metallic salts; but nothing could be found to arrest the fading of the plant juices. Perhaps he would be surprised to know that a number of his experimental specimens retain their images 170 years later, several of them quite striking.

In his 1842 publication Herschel used the term 'vegetable photographs' for these images formed of plant juices, as he did on the wrapper that contains the Oxford specimens (60488, packet 29). The packet however also contains a contemporary slip of paper (23362) on which Herschel has written 'Phytotype (vegetable colours)'. Whether the coinage was an afterthought, or whether he refrained from using it because of his conclusion that it was not a viable process (and would therefore not need a name), we do not know. In the twentieth century, honouring Herschel's note, the word has been adopted and used in the Museum, and is used in this catalogue. Herschel, who was a great coiner of new terms (see additional narrative to 23362) but always fastidiously correct in his scientific language, chose phyto- (plant) because of its already established currency as a scientific prefix. Other writers dubbed his process 'anthotype', from antho- (flower), which historians of photography now more commonly use. Neither word is at present (2010) in the Oxford English Dictionary.

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