When Light Becomes Memory: Cyanotypes and Anthotypes
- Sarah A
- 8 hours ago
- 3 min read
“We reach forth and strain every nerve, but we seize only a bit of the curtain that hides the infinite from us” - Maria Mitchell, astronomer.
Before the age of silver nitrate and the precision of digital sensors, there were gentler ways of coaxing an image into being. Among them were two processes born as a collaboration between the human hand and sunlight: the cyanotype and the anthotype. Both require a slowing of attention. Both techniques ask the same questions science always asks: What is light? What is time?
The cyanotype’s blue is resolute and enduring - it resists time, it insists on remaining. The anthotype, in contrast, fades. Its fragility is its philosophy. The image vanishes slowly. It teaches impermanence by example: that beauty can be brief, and that ephemerality does not negate meaning.
Cyanotypes
In 1842, the English astronomer and philosopher John Herschel discovered that certain iron salts could darken under ultraviolet light. When he coated a sheet of paper with ferric ammonium citrate and potassium ferricyanide, then placed it in the sun, the paper turned a deep shade of blue. Where light was blocked, the paper remained pale. The image that appeared was not drawn but grown.
His friend Anna Atkins, a botanist and collector, recognised in this chemistry something truly special. She began placing algae, ferns, and feathers on sensitised paper and letting the sun inscribe their forms. The resulting work, Photographs of British Algae: Cyanotype Impressions, published in 1843, is often considered the first book illustrated entirely with photographs.
Atkins' work with cyanotypes published in her book Photographs of British Algae: Cyanotype Impressions (1843): Dictyota dichotoma (young), Chordaria flagelliformis, Cystoseira fibrosa, Sargassum bacciferum, Cystoseira granulata, Cystoseira ericoides.
Atkins, Anna, 1799-1871, Public domain, via Wikimedia Commons
The paper must be prepared in near-darkness, then exposed for minutes or hours, depending on the weather. Once rinsed in water, the deep Prussian blue emerges slowly. The alchemy is literal: ferric iron becomes ferrous, and Prussian blue blooms on paper. It is a print that carries the scent of its origin. It carries the path of a photon.
Creating a blueprint of fleeting things.
Photos: Sarah A.
In the first step of photo reduction, the ferric ammonium citrate contains Fe³⁺ bound in an organic matrix. UV light reduces Fe³⁺ to Fe²⁺ (needed for image formation) while oxidising citrate. The Fe²⁺ created above reacts with ferricyanide to form ferrocyanide and then precipitates as Prussian blue.
Cyanotypes of Indian sea algae: Sargassum sp., Galaxaura sp., Halimeda sp. on water colour paper.
Cyanotypes by Sarah A.
Cyanotyping photos (using negatives) and garden finds. Photo: Sarah A.
Anthotypes
The anthotype emerged as a transient process to the cyanotype. Instead of iron salts, it relies on the pigments of plants. Petals, leaves, or berries are crushed and mixed with alcohol or water to create a light-sensitive emulsion. The paper, brushed with this colour, is then left to the sun.
Photos by Sarah A
The physicist James Clerk Maxwell once wrote that colour exists not in objects but in the mind that perceives them. The artist Georgia O’Keeffe, painting half a century later, echoed the same intuition when she said she painted flowers so people would truly see them. Both spoke to the same hunger: to make visible the intimacy between perception and existence.
In anthotypes, plant pigments such as anthocyanins (found in berries, beetroots, etc), chlorophyll (found in green leaves, spinach), curcuminoids (found in turmeric) are photobleached (degraded) using sunlight. Where the paper is exposed, a higher pigment breakdown results in fading; where the subject blocks the light, the pigment remains intact. The image is essentially the difference between bleached and unbleached pigment.
Where the cyanotype gives permanence, the anthotype accepts impermanence. Perhaps this is what all art rooted in science reminds us: that knowledge and wonder are not opposites. The cyanotype and the anthotype, blueprints of curiosity, reveal the world as it is, and as it might be seen if we slowed down enough to notice the quiet transformations happening everywhere light touches matter.
Light writes us, too.
In every cell, a little photosynthesis continues. In every act of seeing, we participate in the same physics that turns leaf-shadow into art.
About the author:
Sarah is a silly goose, who waddles through life with a microscope in one hand and a paperback in the other. She loves exploration, science, maps and swears by Lord of the Rings. 🏴☠️