A lumen print is a contact print made only using sunlight on black and white photographic paper. The image is “burnt” onto the paper and then fixed – no developer chemicals are used.
A cyano-lumen is a combination print. Cyanotype fluid is used to coat the black and white photographic paper under safelight conditions. Once dry the coated paper is then used to form a contact print in the same way as traditional lumens or cyanotypes. The image is then rinsed and fixed.
The silver particulates in the paper react to the long exposure time by clumping to form interesting colour variations. Different manufacturers papers having different colour characteristics.