A lumen print is essentially a solar photogram – a camera-less process involving black and white photographic paper, a subject matter that usually (but not always) consists of an organic material, and of course, the most important element – The Sun. The results will vary due to exposure times, density of photogram or negative, quality of light and, most importantly, the type of paper. Each paper will have a different color, depending on whether it was old or new, fiber or resin, and the manufacturer.