Lumen prints are made by placing plant material directly on out-dated black and white photographic paper. Glass is placed over the flora and paper, then exposed to direct sunlight for 1 to 6 hours .During the exposure, heat, moisture and chlorophyll affect the photographic paper producing a colored image. After the desired exposure the prints are fixed and then washed.
Lumen prints resemble photograms but differ in that they are “printed out” images meaning the image prints out from the paper. This is the opposite of photogram images, which are “developed out” using chemicals in the darkroom.