Cyanotype is a photographic printing process that produces images in a distinctive Prussian blue. It is one of the earliest non-silver photographic methods, invented by Sir John Herschel in 1842, and widely used for both artistic and scientific applications.
Cyanotype is a contact printing process that uses light-sensitive iron salts (ferric ammonium citrate and potassium ferricyanide). When exposed to ultraviolet light and then washed in water, the chemicals oxidise to form ferric ferrocyanide (blue pigment).
A substrate (usually paper, fabric, or vellum) is coated with a cyanotype solution
A transparent negative or object is placed on the surface
The print is exposed to UV light (e.g. sunlight)
After exposure, it is rinsed in water, fixing the image
Monochromatic: Always blue, unless chemically toned
Direct and indexical: The process creates a 1:1 imprint of the object or negative
Environmentally responsive: Highly sensitive to humidity, temperature, UV intensity, exposure time, and paper type
Low-tech and accessible: Requires no darkroom or expensive materials
Used by Anna Atkins to document botanical specimens—often cited as the first photographic book
Later adopted in architectural blueprints, due to its clarity and reproducibility
Contemporary artists use cyanotype for its material immediacy, tactility, and visual historicity
Cyanotype serves as a model of non-algorithmic computation: it is processual, environmentally contingent, and chemically governed. In your framework, it exemplifies:
Material epistemology: The image is an artefact of atmospheric and temporal conditions—light quality, moisture, and the object’s own opacity all shape the output
Seamful production: The final image retains traces of exposure seams, brushstrokes, and paper irregularities
Indexical modelling: The image does not represent its referent but is produced by direct physical interaction—akin to a model that emerges from proximity, not abstraction
Cyanotype might be thought of as a low-level functor from spatial opacity to chromatic registration—translating the presence or absence of light into a spectral outcome via chemical means. It highlights how environmental and material conditions are not noise but structure, inseparable from the formal qualities of the image.
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