Cyanotype

Description

The cyanotype process was invented by Sir John Herschel in 1842 and used almost immediately by the botanist Anna Atkins to produce Photographs of British Algae (1843) — the first photographically illustrated book in history. The process is iron-based, not silver, so it sits outside the mainstream photographic lineage. It prints in Prussian blue, requires only sunlight to expose, and washes out in water. Architects used it for blueprints (the name "blueprint" comes from the cyanotype). Contemporary photographers, printmakers, and textile artists have revived it as a hand-process medium. Visual rules: a single distinctive Prussian-blue tone with white highlights; no mid-tone range like silver gelatin — contrast is steep, often almost two-tone; objects placed directly on coated paper produce photograms with crisp silhouette edges and soft penumbral halos; sunlight exposure (5–30 minutes typical) means UV-rich light is part of the look; paper texture is always visible because the chemistry coats absorbent fiber; staining, fingerprints, and water-development irregularities are characteristic, not flaws. Use it for botanical and natural-history imagery, textile and pattern design, hand-made book and zine work, scientific-illustration callbacks, and any image that should feel like a physical specimen rather than a photograph. Generative models will give you "blue-tinted photo." Specify "cyanotype photogram on cotton-rag paper, Prussian blue single tone, white highlights, steep contrast almost two-tone, crisp silhouette edges with soft penumbral halo, visible paper fiber texture, hand-coated brush marks at edges, sun-exposed."