Tenebrism is a compositional technique using very pronounced chiaroscuro, in which some areas of a painting are kept completely black, allowing other areas to be strongly illuminated -- usually from a single source of light. The technique was popular during the Baroque period, and Caravaggio is usually credited with invention of the style.
Chiaroscuro is the dramatic effect of contrasting areas of light and dark in an artwork, particularly paintings, to achieve a sense of volume in modelling three-dimensional objects and figures. It comes from the combination of the Italian words for "light" and "dark."
Frottage is a method of reproducing a texture or relief design by laying paper over it and rubbing it with some sort of drawing utensil. The technique was developed by Max Ernst in 1925. Inspired by an ancient wooden floor, the patterns and graining of which suggested strange images to him, he captured these by laying sheets of paper on the floor and then rubbing over them with a soft pencil.
The Blue Period refers to the works produced by Spanish painter Pablo Picasso between 1901 and 1904 when he painted essentially monochromatic paintings in shades of blue and blue-green, only occasionally warmed by other colors. According to the artist himself, this period was an artistic response to his depression over the death of Carlos Casagemas, a friend who shot himself because of an unrequited love for Germaine Pichot who was later depicted in Picasso's Les Demoiselles d'Avignon. "I began to paint in blue," he wrote, "when I realized that Casagemas had died."
Assemblage is an artistic form or medium similar to collage and usually created on a defined substrate that consists of three-dimensional elements projecting out of or from the substrate. It typically uses found objects, but is not limited to these materials.