A brief overview of Lumen photography, an old camera-less process. Lumen is a cameraless technique using silver gelatin paper.
Always be careful when handling chemicals. Read the health and safety instructions.
Black and white photographic papers are used in this process. Some have reported that old, outdated papers work best. This might have to do with age of papers, but also with the emulsion types available years ago, but no longer manufactured.
In any event dig into your photo storage and take those forgotten 20 years old, fogged papers. Have fun with them. Both exposure and development are done with the UV light and sun is the best source.
Place a plant cutting on the paper and leave it in the sun for hours. My exposures vary from about 30 minutes to 4 hours. I place a piece of glass to slightly flatten the plant cutting. In the heat of the summer the photographic paper will get moist in the area of contact with the plant. That is one of the important aspects of producing color shifts. As the exposure progresses the paper will darken.
Try different brands and types of photographic papers. My examples here are made on fiber base, Forte warm tone paper. Typically warm tone papers will produce most interesting color combinations.
Development – none!
After exposure I soak the print for a few minutes in water and then tone if needed. Gold and platinum toners work best for me. I fix in a dilute solution of ammonium thiosulfate. The print will bleach considerably at this point. Toning, especially gold toning helps preserve the delicate colors of the original. Wash the print according to B&W archival standards and admire your artwork.
For some of the best examples look at work of Jerry Burchfield.