Lumen Print

What It Is

Lumen printing uses vintage or expired photographic silver gelatin paper — the same paper used for darkroom black and white printing. When exposed to sunlight (without any developer), the silver halides in the paper slowly reduce to metallic silver, creating a colour image. The colours produced — yellow, orange, pink, purple, brown — come not from applied dyes but from the partial reduction of silver halides at different rates, influenced by the organic chemistry of whatever is placed on the paper.

Unlike cyanotype or anthotype, lumen printing requires no coating preparation. Any silver gelatin photographic paper works — often expired paper gives better results, as the degraded emulsion produces more unpredictable and vivid colour ranges.

Process

From the San Casciano workshop (Almudena Romero, Day 3, 2025):

1. Collect botanical materials — leaves, petals, ferns, grasses, seed pods, or any flat organic form.
2. In subdued indoor light, place objects directly on the paper's emulsion side (the shinier side).
3. Cover with glass to ensure full contact between object and paper.
4. Expose in direct sunlight. Exposure time: 5 minutes to several hours depending on UV intensity, paper type, and desired result. Check periodically.
5. When satisfied, remove objects and either fix immediately (sodium thiosulphate fixer) or scan/photograph before fixing — the unfixed image will continue to change and eventually fade to overall brown.

Cyanolumen

A hybrid process combining cyanotype and lumen printing: coat the paper with cyanotype sensitizer, dry, then expose with objects. The iron chemistry of cyanotype produces a blue ground; the lumen process adds warm organic colours from the botanical objects. The result combines the structural blue of cyanotype with the warm, unpredictable tones of lumen.

Fixing and Preservation

• Fixer (acid): Sodium thiosulphate solution (standard photographic fixer). 4–6 minutes. Removes remaining unexposed silver halides, stabilizing the image.
• Water wash: Wash thoroughly after fixing.
• Unfixed lumen: Deliberately unfixed lumen prints continue to change — darkening, shifting color over months or years. Used as time-based work.
• Scan before fixing: The pre-fixed colours are often more vivid and warm than the post-fixed result. Many artists scan or photograph before fixer.

Caffenol — Sustainable Developer

Caffenol is a photographic developer made from coffee, washing soda, and vitamin C — household chemicals replacing commercial darkroom developer. Used in the San Casciano workshop as a sustainable alternative. Coffee grounds (used) work slightly differently from fresh coffee. Processing time varies (30–60 min in caffenol versus 2–3 min in standard developer).

Common Failures

• Pale, low-contrast result: Insufficient UV exposure. Increase time or work in higher-UV conditions (summer, midday, high altitude).
• Image fades before fixing: Sun re-exposure after removing objects continues to bleach the image. Move indoors or work under red/orange safelight after removing objects.
• Image turns uniformly brown: Over-exposed or unfixed image that has continued to reduce. Normal for unfixed time-based lumen work.

Jay's Studio Note

Lumen printing was introduced on Day 3 of the San Casciano workshop as a process of maximum uncertainty — the artist sets conditions and then steps back. The paper does the rest. The coffee-and-washing-soda caffenol developer, made from the workshop kitchen supplies, connected the photographic process back to the same material logic as the bioplastic and natural dye work: using what is already there, in the environment, to make the image.

Related Materials

Cyanotype · Anthotype · Chlorophyll Printing · Watergram