Spray paint art
Spray paint art uses spray painting on a non-porous material, such as wood, metal, glass, ceramic or plastic.
Spray paint art is usually street art, in large cities. Themes may include surreal landscapes of planets, comets, pyramids, cities, and nature scenes. The pieces can have a simple one-colored background or a multi-colored backgrounds in which the paint swirls together or fades from one color to the other through a series of differing values of each color. It is said to have originated in Mexico City in the early 1980s. 
-  "Spray-paint artists have exploded onto the scene - but is it art?" (Knight Ridder/Tribune News Service Article date: December 8, 2003 Author: Robinson, Gaile Copyright COPYRIGHT 1999 Knight-Ridder/Tribune News Service)