What is a cyanotype?

A cyanotype is a photographic print in deep blue. The astronomer and scientist Sir John Herschel described the process in 1842. Paper is brushed with two iron salts, ferric ammonium citrate and potassium ferricyanide, and left to dry in the dark. Wherever light reaches the coated paper, the salts turn into an insoluble blue pigment, Prussian blue. Rinsing the sheet in water washes away the unexposed coating and leaves the image.

Anna Atkins and the first photographic book

A year later the botanist Anna Atkins began to use the process for her Photographs of British Algae: Cyanotype Impressions, issued in parts from 1843. She laid seaweeds directly on the coated paper and let the sun do the rest, so each plate shows a white silhouette on blue. It is generally counted as the first book illustrated with photographs. That plate-on-blue look is what we call a photogram.

Why it is blue, and why it looks hand-made

The colour is the pigment itself, not an ink. Because the coating is brushed on by hand, a cyanotype usually shows a ragged edge, uneven density and the odd stain. Later the same chemistry made engineers’ “blueprints”. Artists still use it because it is simple, permanent and very hard to make look mechanical.

Cyanotypes at TirajArt

We do not coat paper: our cyanotypes are made in Tiraj, our own printmaking software, from public-domain museum images. It rebuilds the brushed coating, the tonal range of Prussian blue and the paper fibre. There are two kinds: blue images on pale paper, such as Polypodium Phegopteris, and white photograms on blue after Atkins, such as Crown Imperial.

How to hang them

Cyanotype blue is strong. A single print holds a wall on its own; three together look calm if they share the same ground, all pale or all blue. The Blue Garden set mixes both: a dark photogram between two pale prints. Print on white matte paper so the blue stays clean.