Cyanotype Quiz – Alternative Process Photography Knowledge

Cyanotype sensitizer is prepared by mixing two solutions, one containing ferric ammonium citrate and the other containing potassium ferricyanide. When mixed and coated on a surface, the combined chemistry reacts to UV light to form the characteristic blue-cyan image.

Light is the foundation of every image. Hard light creates sharp shadows and contrast; soft light wraps around and minimizes wrinkles. Knowing how to read light and position yourself or modify it is more important than any technical setting.

UV exposure causes the ferric iron in the sensitizer to reduce to ferrous iron, which then reacts with the ferricyanide to form ferric ferrocyanide, a compound known as Prussian blue. This reaction is self-fixing: the wash step removes only the unreacted sensitizer, leaving the stable blue compound in the exposed areas.

Water dissolves the unexposed ferric ammonium citrate and potassium ferricyanide that did not form stable Prussian blue during UV exposure. The wash removes this yellow-green residue, revealing the bright white and blue image. No chemical fixing bath or stop bath is required.

Cyanotype sensitizer can be coated onto any surface that absorbs and holds liquid: watercolour paper, cotton fabric, linen, unfinished wood, and other porous materials. The versatility of the substrate is a major reason the process is used in craft, fine art, and alternative process photography.

A digital negative is an inkjet-printed transparency of the inverted image. When laid over sensitized paper and exposed to UV light, it blocks or transmits light proportionally to the image's tones, transferring a photographic tonal range rather than the simple shadows of a physical photogram.

Light is the foundation of every image. Hard light creates sharp shadows and contrast; soft light wraps around and minimizes wrinkles. Knowing how to read light and position yourself or modify it is more important than any technical setting.

Prussian blue oxidises further when exposed to hydrogen peroxide or air, deepening the blue and increasing shadow density. Applying a dilute peroxide rinse or simply hanging the print to air-dry accelerates and completes this oxidation, boosting the maximum density and perceived contrast.

Prussian blue is pH-sensitive and bleaches or shifts in colour under acidic conditions. Applying vinegar or citric acid solution to a fixed cyanotype destroys the blue in treated areas, producing a bleaching effect. Neutralising with a wash and then re-exposing or toning allows the photographer to work into the image.

Sir John Herschel discovered the cyanotype process in 1842 while researching light-sensitive iron compounds. The process predates many better-known photographic methods and became widely known through Anna Atkins, who used it to create the first photographically illustrated book.