Chrysotype Photography Guide — Iron-Gold Printing Process Explained

The chrysotype is one of the rarest and most historically fascinating photographic printing processes — an iron-gold process invented by Sir John Herschel in 1842, just three years after the announcement of photography itself. The name comes from the Greek chrysos (gold): the image is composed of colloidal gold, producing prints in rich purple, blue, magenta, and violet tones depending on the particle size and the chemistry used. Herschel's original process was frustratingly unpredictable and was largely abandoned. In the 1990s, Dr Mike Ware reinvestigated the chemistry and developed a reliable modern chrysotype process that produces stunning, permanent prints in a palette of colours unique among photographic processes. Gold is the most stable of all metals, making the chrysotype one of the most archivally permanent photographic processes in existence. This guide covers the history, Herschel's pioneering experiments, Ware's modern reformulation, chemistry, technique, and the extraordinary beauty of chrysotype prints.

Herschel's Invention and the Problem of Unpredictability

John Herschel — the polymath who also invented the cyanotype and coined the terms "photography," "negative," and "positive" — was fascinated by the photographic potential of gold salts. He demonstrated that ferric iron compounds, when reduced by light to ferrous iron, could in turn reduce gold salts to metallic gold. The resulting colloidal gold particles formed a visible image on paper. However, Herschel found the process maddeningly inconsistent — the gold would sometimes reduce too quickly, fogging the paper; the colours varied unpredictably; and the sensitised paper had a very short shelf life. Herschel never achieved reliable results and moved on to other experiments. The chrysotype remained a historical curiosity for 150 years.

Mike Ware's Modern Chrysotype

Dr Mike Ware approached the chrysotype with the tools of modern chemistry. He identified the sources of Herschel's problems — unstable sensitiser solutions, uncontrolled gold reduction kinetics, and inadequate fixing — and reformulated the process using gold(III) sodium thiosulphate as the gold source and ammonium iron(III) oxalate as the photosensitive agent. Ware's chrysotype sensitiser is more stable, the gold reduction is controllable, and the resulting images are reliably beautiful. The modern chrysotype produces prints in a range of colours from cool blue-grey through purple to rich magenta, depending on the concentration of the gold salt, the paper used, and the development conditions. The gold image is extraordinarily permanent — gold does not tarnish, oxidise, or react with atmospheric pollutants.

Process and Technique

Coat high-quality fine art paper (COT 320, Arches Platine, or similar) with the chrysotype sensitiser under safelight. Dry. Expose under UV light through a contact negative. The chrysotype is a developing-out process — little or no image is visible until development. Develop by immersion in a dilute bath that promotes gold particle formation. The image appears in deep purples, blues, or magentas. Clear in dilute acid to remove iron residues. Wash thoroughly. The resulting print is a precious object — literally made of gold — with a colour palette uniquely its own and a permanence that exceeds all silver- and platinum-based processes.

The Chrysotype Aesthetic

Chrysotype prints are unlike any other photographic process in colour. The rich purple, violet, and magenta tones — caused by the specific optical properties of nano-scale colloidal gold — are strikingly beautiful and completely unique. The matte, embedded quality of the image within the paper fibres, combined with the extraordinary permanence of gold, makes the chrysotype a jewel among photographic processes. The process is rare, expensive (gold salts are not cheap), and technically demanding — but it produces objects of irreplaceable beauty and historical resonance, connecting the modern printer directly to Herschel's earliest experiments with the chemistry of light.