Lumen prints are made by placing flora of one kind or another directly on B/W photographic printing paper. Glass is placed over the flora and paper and then the paper is exposed to direct sunlight for 4 to 6 hours or more. During this exposure period the moisture and chlorophyll affect the photo paper surface and impart some soft colors, depending upon the flora that is chosen. 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.