Printing with plants is growing in popularity since it is sustainable and easy to learn. Mike Ware gives us an overview of the difference between anthotypes, photosynthesis and chlorophyll printing.
In January of 1839, the invention of photography was publicly announced, independently by Louis Daguerre using silver-plated metal sheets, and by William Henry Fox Talbot, using writing paper coated with silver salts. Within a week, Talbot’s colleague in the Royal Society, the leading scientist Sir John Herschel, had taken up research into the discovery. Although silver photochemistry has always provided the most sensitive materials for mainstream photography, there have also been episodes during its history when plant substances were used to record images photographically.
Anthotype or Phytotype
Herschel was not entirely satisfied with the brown pictures provided by Talbot’s silver process so, seemingly driven by a desire for a system of colour photography, he set out on a quest for new imaging photochemistry. In September 1839 he first employed the plants and flowers from his own garden, such as common heartsease (viola tricolor). He crushed the petals in alcohol to extract solutions of the dyestuffs (called anthocyanins), which he then painted onto paper as light-sensitive coatings to be exposed to the solar spectrum1. In over two hundred such coating experiments conducted between 1839 and 1842, Herschel demonstrated the feasibility of directly printing positive photographic images by bleaching these plant dye papers with sunlight. Exposure in contact with engravings yielded monochrome prints in various colours – depending on the plant – which Herschel must have hoped would supply the primaries for a full-colour printing system. He dubbed this new process ‘anthotype’ (Greek: ανθος = ‘flower’) or sometimes, ‘phytotype’ (Greek: φυτον = ‘plant’).
The process proved too insensitive for the camera, however, and even the contact printing was very protracted, demanding exposures of hours or even days to bright sun2. Moreover, the resulting pictures were ephemeral: there was no effective means to fix such images because further exposure to light would slowly but inexorably fade them, owing to the fugitive nature of these plant dyes. It is remarkable that a few of Herschel’s anthotype images have survived the 180 years to the present day, to be seen now in the collections of the Museum of the History of Science, Oxford3, and the Harry Ransom Humanities Research Center, University of Texas, at Austin.
To the enduring benefit of the embryonic science of photography, the spring weather of 1840 was remarkably brilliant. Herschel initiated a new series of exposure tests of his ‘vegetable colours’, but this work was interrupted in March by the relocation of the family home from Slough in Buckinghamshire to Hawkhurst in Kent. Once resettled, Herschel resumed his experiments in August, but by then he frequently found the sun to be ‘pale’ or ‘desultory’, requiring long exposures for these very insensitive processes4. He pursued them nonetheless, during the very poor summer of 1841 that followed. The sun was, of course, the only practicable light source available to the early pioneers of photography, and all experiments were at the mercy of the vagaries of the weather. It seems clear from the nature of Herschel’s investigation of the bleaching of these coloured plant juices by light, that he was in pursuit of a direct positive-working colour photographic process, and he stated as much in one of his letters to Talbot5, and in a letter to the 1841 Meeting of the British Association for the Advancement of Science, reporting on these experiments:
“ … a circumstance which … holds out no slight hope of a solution of the problem of a photographic representation of natural objects in their proper colours.6”
The most important conclusion that Herschel was able to draw from his observations was that a dye tends to be selectively bleached by the light of its complementary colour, which was further evidence for the Grotthuss law of photochemical absorption.
By the early spring of 1842, these rather evanescent organic plant dyes were proving unsatisfactory, so Herschel discontinued testing them in favour of further broadening his search for new photosensitive substances for his ‘non-argentine photography’. His attention transferred to deeply-coloured compounds of iron, which eventually led him to his celebrated process in Prussian blue which he named ‘cyanotype’, and several other remarkable iron-based (or ‘siderotype’) processes. Herschel’s plant-based photography was however carried on and taken further by the redoubtable Scotswoman, Mary Somerville (née Fairfax) the founder of the eponymous Oxford women’s college, whose researches were reported to the Royal Society in 1846 by Herschel himself7.
Thereafter, with the development of silver halides as the most successful photographic medium for the next 150 years, the use of plant materials fell by the wayside – until modern times. Since the artistic renaissance of ‘alternative’ processes for photography during the 1990s, there has been a growing constituency of practitioners in this environmentally friendly and sustainable – but potentially impermanent – photographic medium of anthotype. Aspiring practitioners of the process can now find full practical instructions in the informative manual by Malin Fabbri8.
Living and growing plants also provide opportunities for proto-photography. The following two early instances were recorded by Charles Maybury Archer in his Anecdote History of Photography of 18609:
“Mr. Septimus Piesse has called attention to the delicate shading or finishing of leaves produced by the photographic touch of the sun, in the case of geranium and other leaves, where one leaf produced a shade upon the other, the under leaf presenting a beautiful photograph of the upper one, its serrated edge and form being perfectly defined. Wherever the shade was cast, that part of the leaf was of a deep green, while the unshaded parts were of a pale sea-tint.”
“The first principles of a peculiar photographic process were discovered in 1845 by M. Bayard, on the amber and purple surface of a peach. Proud of his peaches, M. Bayard, it is said, was accustomed to mark them with his initials. To effect this he was in the habit of gumming on to the surface his initials cut in small paper characters, and which, under the action of the autumn sun, left their impression on the ripening fruit.”
A latter-day version of this ‘photosynthetic photography’ has been devised since 1990 by two contemporary artists, Heather Ackroyd and Dan Harvey. They project the image of a photographic negative with a very powerful (2.5 kW) lamp onto a vertical ‘field’ of growing grass seedlings, which consequently develop a richer green where the light falls due to a higher concentration of chlorophyll, so providing a positive image.
Because the grass is seeded on a vertical wall it tends to grow upwards, revealing the entire blade instead of just the tip, as a surface to collect the light. The exposure usually takes about eight days. The pieces are quite ephemeral, sometimes lasting only a week, but the artists have recently found a type of grass that stays green much longer than most10.
The photosynthetic photographic process just described employs light to promote the synthesis of chlorophyll within the growing plant; not to be confused with this is the converse photographic practice popularly called ‘chlorophyll printing’, in which sunlight actually bleaches a recently plucked plant leaf, thus providing a positive photographic image if an object or diapositive is interposed between the two.
This printing process is relatively easy to perform: it is simply a destruction by light (especially containing UV radiation) of the same ubiquitous plant pigment, chlorophyll, by a photo-oxidative degradation. So it provides a positive-working imaging process just like the anthotype, but with the difference that a large natural plant leaf, such as a hosta, itself provides the pigmented cellulose substrate for the image, rather than a coated sheet of man-made paper.
The Vietnamese artist Binh Danh is a prime exponent of chlorophyll printing;11 he makes use of single large leaves, photo-bleached in contact with diapositives, and finally sealed into polymer resin blocks to improve their durability. Current research is seeking to improve methods of fixation of chlorophyll prints by de-oxygenation and the incorporation of copper(II)12.
Finally, as an apocryphal footnote to this account of light-sensitivity in natural organic materials, there is the following myth which is often related at an early stage to students of photochemistry: Alexander the Great was said to have exploited light-induced colour changes in a plant dye, in order to coordinate the battle-order of his army, which proved crucial to the success of his campaigns. The Macedonian troops supposedly wore around their wrists bands of rag impregnated with a photochromic dye. Their exposure to the light of the rising sun caused a colour change which signalled the moment of attack. This device has become known as Alexander’s Rag Time Band13.
- Sir John F.W. Herschel, ‘On the Chemical Action of the Rays of the Solar Spectrum on Preparations of Silver and other Substances, both metallic and non-metallic, and on some Photographic Processes’, Philosophical Transactions of the Royal Society of London, 1840, 131, 1-59.
- Sir John F.W. Herschel, ‘On the Action of the Rays of the Solar Spectrum on Vegetable Colours, and on some new Photographic Processes’, Philosophical Transactions of the Royal Society of London, 1842, 132, 181-215.
- Sir J.F.W. Herschel, MS Notebook, vol. III, Science Museum Library, London.
- Letter, Herschel to Talbot, 21 April 1842. NMPFT 1937-4900. See L.J. Schaaf, (ed.), Selected correspondence of William Henry Fox Talbot 1823-1874, (London: Science Museum and National Museum of Photography, Film & Television, 1994), 36.
- ‘Letter from Sir John F.W. Herschel, dated July 31, 1841’, Report of the Meeting of the British Association for the Advancement of Science, Transactions of the Sections (Plymouth: 1841), p40.
- Mary Somerville, ‘On the Action of the Rays of the Spectrum on Vegetable Juices. Extract of a Letter from Mrs. M. Somerville to Sir J.F.W. Herschel, Bart. dated Rome, September 20, 1845. Communicated by Sir J. Herschel,’ Philosophical Transactions of the Royal Society of London, 136, 1846, 111-120.
- Malin Fabbri, Anthotypes, Stockholm: Alternativephotography.com, 2012.
- C.M. Archer, ‘The Anecdote History of Photography’, in W.B. Tegetmeier (ed.), Recreative Science: a record and remembrancer of intellectual observation, Vols 1 and 2. (London: Groombridge and Sons, 1860/1). 187, 231, 244, 348.
- Barbara Morais, ‘How to Preserve Chlorophyll Prints’
- The Xotype Files: http://www.mikeware.co.uk/xotype.html
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