Solar Plate is the name some fine art printmakers have given to a new method of making relief or intaglio prints from a photosensitive material originally developed for the commercial printing industry (where it is used in a process called flexography). The technical name of this material is "photopolymer".
Photopolymer is sensitive to sunlight or Ultra-Violet (UV) light – not to artificial light. So there is no need for a darkroom. The plates can be prepared indoors and then taken outside for a timed exposure (this varies from a few minutes in summer sunshine to up to half an hour on a dull winter’s day).