Mordançage — The Dark Art of Bleach-Etch Printing in the Darkroom

Mordançage is one of the most dramatic and mysterious darkroom techniques in all of photography — a chemical process that selectively bleaches and lifts the dark areas of a silver gelatin print, creating veils and blisters of lifted emulsion that can be peeled away, reshaped, or left in place to produce images of haunting, surreal beauty. The mid-tones remain intact while the deepest shadows and darkest tones dissolve and blister, producing an inverted relief — like a photographic bas-relief emerging from the paper. The technique was pioneered in the early twentieth century and refined by artists like Jean-Pierre Sudre, who used mordançage to create luminous, otherworldly prints that blur the boundary between photography and sculpture. This guide covers the chemistry, process, creative possibilities, and practical tips for producing mordançage prints.

How Mordançage Works

A fully developed and fixed silver gelatin print is immersed in a mordançage solution — a mixture of potassium bromide, copper chloride or copper sulphate, and glacial acetic acid in water. The solution selectively attacks the dark silver deposits in the emulsion. In the darkest areas, the chemical reaction produces silver bromide — the same compound that forms the light-sensitive crystals in unexposed paper — and the gelatin emulsion swells, blisters, and lifts away from the paper base. The mid-tones and highlights, which contain less silver, are less affected. The result is a print where the dark areas have been partially dissolved and physically displaced — creating veils, wrinkles, and bubbles of lifted gelatin that cast shadows and catch light in three-dimensional ways that flat printing cannot achieve.

Chemistry and Preparation

The standard mordançage bleach solution consists of: 50g potassium bromide, 10ml glacial acetic acid (concentrated), 5g copper sulphate (or copper chloride), dissolved in 1 litre of water. Mix carefully — glacial acetic acid is concentrated and corrosive. Use proper ventilation and protective gloves. The solution should be prepared fresh; it deteriorates over time. You also need standard photographic developer (to redevelop if desired) and fixer. Work in a well-ventilated area — the acetic acid produces strong fumes, and the copper compounds are toxic. Use separate trays for the mordançage solution, developer, fixer, and rinse water. Never mix mordançage chemicals into your regular processing trays.

Step-by-Step Process

Begin with a fully processed silver gelatin print — developed, stopped, fixed, and washed. The print should have good dark tones (Zone II–III) because mordançage works on the silver density in these areas. Soak the print in water for several minutes to soften the gelatin. Immerse the wet print in the mordançage bleach solution. Watch carefully: within 30 seconds to several minutes, the dark areas will begin to lighten and the gelatin will start to blister and lift. The timing depends on the silver density, paper type, and solution strength. When the blistering reaches the desired extent, remove the print and rinse in running water. At this point, you have several creative options: leave the lifted gelatin in place (producing translucent veils), peel or scrape the lifted areas away (revealing white paper beneath), redevelop the print to rebuild tone in the bleached areas, or manipulate the lifted gelatin with tools.

Creative Options After Bleaching

The artistic power of mordançage lies in what you do after the bleach. Option one: peel the lifted emulsion away entirely, revealing bare white paper where the darkest tones were. This creates an eerie tonal inversion — the deepest shadows become the lightest areas. Option two: leave the veils in place. The lifted gelatin forms translucent curtains and bubbles that hover above the paper surface, creating depth, shadow, and a sculptural quality. When the print is dried, the veils collapse flat but retain their wrinkled, textured character. Option three: redevelop the print after mordançage. Immerse in standard developer — the silver bromide created by the mordançage is still light-sensitive and will redevelop into dark silver, rebuilding tone in the bleached areas. This can produce solarisation-like tonal effects with edge lines and partial reversals. Option four: combine options — peel some areas, leave veils in others, and selectively redevelop.

Paper Selection

Fibre-based (FB) papers produce the best mordançage results. The thick, absorbent paper base allows the gelatin to lift and blister more dramatically than on resin-coated (RC) paper, where the plastic base restricts emulsion movement. Warm-tone papers (such as Ilford Multigrade Warmtone FB) produce particularly beautiful results — the warm silver tone combines with the mordançage effects for a rich, antique quality. Double-weight FB paper is preferred for durability — the print must withstand extensive wet handling. Papers with high maximum density (Dmax) produce the most dramatic blistering because there is more silver for the mordançage to attack. Glossy papers show the lifted emulsion texture more clearly; matte papers produce subtler effects.

Subjects That Work Well

Mordançage is most effective on images with strong tonal contrast — deep blacks and clear whites. Portraits with dark backgrounds are classic mordançage subjects: the dark background blisters and lifts while the lighter face remains intact, creating a portrait emerging from a sea of wrinkled, dissolved darkness. This produces an effect that is simultaneously beautiful and unsettling — the face seems to float in a decomposing field. Botanical subjects with dark leaves and bright flowers work beautifully. Architectural images with strong shadow areas produce dramatic stripping effects. Nudes against dark backgrounds allow the skin tones to remain pristine while the surrounding darkness transforms. Avoid images that are predominantly mid-tone — mordançage needs strong darks to have sufficient silver to attack.

Solarisation vs Mordançage

Mordançage and solarisation (Sabattier effect) are often combined. After the mordançage bleach and rinse, exposing the wet print to room light and then redeveloping produces a combined solarisation-mordançage effect — Mackie lines (bright edge lines between tonal regions) appear alongside the mordançage stripping and blistering. The combination produces some of the most visually complex and surreal images possible in the traditional darkroom. Jean-Pierre Sudre was a master of this combined technique, producing prints of extraordinary luminosity and otherworldly beauty. The process is unpredictable and requires experimentation — each print and each combination of bleach time, light exposure, and redevelopment produces unique results.

Safety and Best Practices

Wear chemical-resistant gloves at all times — the copper compounds and concentrated acetic acid are toxic and corrosive. Work in a well-ventilated space — the acetic acid fumes are strong and irritating. Use separate, labelled trays for the mordançage solution to prevent cross-contamination with regular processing chemistry. Dispose of mordançage chemicals responsibly — copper compounds should not be poured down the drain. Contact your local hazardous waste facility for disposal guidance. Handle wet prints carefully — the swollen, blistered gelatin is fragile and tears easily. Use print tongs or lift prints by the edges. Have clean water available for immediate rinsing if chemicals contact skin.