Overview

Lumen printing is a camera-less photographic process that uses expired or outdated black-and-white photographic paper exposed directly to sunlight. Objects placed on the paper block light, creating photograms with unique colours and tones that emerge from the paper's degraded silver halides.

How It Works

Unlike traditional darkroom printing where paper is exposed briefly and then developed, lumen prints are exposed for extended periods (hours) in direct sunlight without chemical development. The image forms through direct photochemical action—a "printing out" process similar to historical techniques.

The colours that emerge—pinks, purples, browns, oranges—result from:

The paper's age and storage conditions
Organic material in contact with the emulsion
Moisture levels during exposure
Exposure duration and UV intensity

Materials

Paper

Expired black-and-white photographic paper (the older, the better)
Different brands/types produce different colour palettes
Fibre-based paper often produces richer colours than RC
Store paper improperly (warm, humid) to accelerate colour potential

Objects

Anything that blocks or filters light:

Botanical materials (leaves, flowers, feathers)
Translucent objects (glass, fabric)
Found objects
Negatives (for more traditional photographic images)

Contact Frame

Glass-topped frame to hold objects flat
Or simply glass and backing board with clips

Basic Process

Setup: In subdued light, place objects on photographic paper, emulsion side up.
Contact: Cover with glass to ensure firm contact.
Exposure: Place in direct sunlight, typically for about 30 minutes to 4 hours (longer exposures shift the colours further).
Assessment: Check periodically—colours shift and develop over time.
Optional fixing: Fix in a dilute ammonium thiosulfate fixer to make the print stable (expect it to bleach considerably and the colours to shift; Matusz gives no dilution or time), or leave it unfixed and scan it immediately.

Fixing Considerations

Unfixed Prints

Retain full colour range (pinks, purples, oranges)
Will continue to change with light exposure
Must be stored in complete darkness
Scan or photograph immediately to preserve colours

Fixed Prints

Fixing shifts colours dramatically—usually toward brown/sepia
Removes most of the pink/purple tones
Print becomes light-stable
Traditional archival properties

Partial Fixing

Some practitioners fix only briefly, as a compromise between colour retention and stability. There is no standard time, so test on scrap prints.

Colour Palette

Different papers and conditions produce different colours:

Factor	Effect
Paper age	Older paper often produces more colour
Storage conditions	Heat/humidity accelerate colour potential
Botanical contact	Organic materials react with emulsion, creating colour
Moisture	Wet botanical materials intensify colour reactions
Exposure length	Longer exposures deepen and shift colours

Common Colours

Pinks/magentas: Often from fresh botanical material
Purples: Extended exposure, certain paper types
Oranges/browns: Very long exposures, fixed prints
Yellows: Some paper types, certain plant materials

Advanced Techniques

Wet Lumen Prints

Placing botanical material on paper while wet intensifies chemical reactions between plant material and silver halides, often producing more vivid colours.

Toning Unfixed Prints

Gold or platinum toning can alter the colours and help preserve them (Matusz soaks the print in water for a few minutes first, then tones before the dilute fix).

Multiple Exposures

Moving objects during exposure or re-exposing with different objects creates layered imagery.

Combination with Other Processes

Some practitioners coat lumen prints with cyanotype or other emulsions for multi-layered work.

Technical Considerations

Exposure Time

Typical: about 30 minutes to 4 hours in bright sun
Extended: from several hours to days; exposures of up to two months have been tested
In one comparison (5 minutes, 30 minutes, 2 days and 2 months on Fomatone MG Classic), the 30-minute print was among the most balanced

Season and Location

Summer sun produces faster, more intense results
Winter/overcast requires longer exposures
Altitude and latitude affect UV intensity

Paper Selection

Experiment with different papers:

Ilford Multigrade
Kentmere
Kodak Polycontrast (discontinued in 2005; expired stock only)
Oriental
Expired papers from any manufacturer

Each behaves differently. Build a collection of expired papers for varied results.

Documentation

Because unfixed lumen prints continue to change, many practitioners:

Scan immediately after exposure at high resolution
Photograph under controlled lighting
Keep detailed notes on paper type, exposure, and conditions
Accept that the physical print is ephemeral

Characteristics

Camera-less (photogram technique)
Unique colour palette impossible with conventional processes
Each print is one-of-a-kind
Meditative, slow process
Environmentally connected (sun exposure, botanical subjects)
Uses materials otherwise destined for disposal

Safety

Material	Hazard	Precautions
Photographic paper	Minimal	None required
Fixer (if used)	Mild irritant	Gloves recommended; normal darkroom ventilation

Lumen printing is one of the safest photographic processes, requiring no hazardous chemicals for the basic process.

Tips for Success

Collect expired paper — ask at photo labs, buy cheaply online
Use fresh botanical material — it produces more colour than dried
Try wet processes — moisture intensifies colour reactions
Expose longer than you think — colours continue to develop
Scan before fixing — you can always fix later, but you can't unfix
Keep notes — with so many variables, records help you learn

Historical Context

While not a historical process per se, lumen printing connects to the earliest days of photography when images were "printed out" by direct light action rather than chemical development. It also echoes the photogram experiments of Man Ray and Moholy-Nagy, applying their camera-less approach to a medium that generates its own colour palette.

Sources

Lumen prints, AlternativePhotography.com (Marek Matusz)
Lumen Printing: How Exposure Time Changes the Image, AlternativePhotography.com
Kodak black and white paper discontinued, Photography Blog (2005)
The Experimental Darkroom, Routledge

This guide combines established practice with community experience. Always follow safety precautions and cross-reference with primary sources before mixing chemicals.

Lumen Prints

At a glance

Image characteristics

Key chemicals