Watercolour (Gumprint)

Watercolour gum (gumprint, gum bichromate print) is one of the most versatile and oldest photographic processes. Its principle was discovered by Mungo Ponton in 1839, who observed that paper soaked in potassium bichromate hardened under light. It was Alphonse Poitevin who, in 1855, had the idea of mixing watercolour pigment with sensitised gum arabic: by exposing this layer under a negative, the exposed areas harden and retain the pigment while unexposed areas dissolve during washing.

The gumprint enjoyed its golden age between 1890 and 1920, within the Pictorialist movement. Photographers such as Robert Demachy, Edward Steichen, and Gertrude Käsebier used it to create images halfway between photography and painting, asserting photography as a fine art in its own right. Each colour layer is applied, sensitised, and exposed individually — a four-colour print therefore requires a minimum of four passes.

At Picturale, we have reformulated gumprint chemistry to make it 100% non-toxic and workshop-safe, while preserving the chromatic richness and depth characteristic of the process.

The gumprint made by Maison Picturale is an entirely handmade print where each colour layer is a unique pictorial gesture.

We work on 100% cotton satin watercolour paper at 640 g/m², capable of withstanding multiple watercolour passes without warping. In four-colour mode, each print requires four successive layers — cyan, magenta, yellow, and black — each individually sensitised, exposed, and developed. The result is an image with vibrant colours and a grain impossible to achieve with digital printing.

The gumprint also comes in monochrome (single colour) and sanguine (brick-red to burnt sienna tones), offering a range of renderings from Old Master drawings to contemporary watercolour.