When framing, be sure the mat board is alkaline free and use UV glass or plexiglas. Cyanotypes are alkali sensitive. The bright blue image will fade if matted, framed or stored in an alkaline environment. Once faded, it will not return. Cyanotypes should not be exposed to strong sunlight. If this occurs, place the cyanotype in a dark environment for a few weeks to recover to its original blue. A good practice is to let it rest in the dark every so often.