Watercolor
Watercolor is a water-soluble painting medium traditionally applied to paper in thin layers with a soft brush. The principle components of the paint are a gum binder (gum arabic or gum acacia) and pigment for color. Watercolor paints are made in both transparent and opaque forms, but when not specified, the term 'watercolor' generally refers to the transparent form. (The opaque form, identical in composition except with added pigment or chalk, is called gouache.) High quality watercolor paints are semi-liquid and packaged in tubes, while student and hobbyist grades usually appear in sets of dry pans of color. Either form requires the artist to add water to bring the paint to a usable consistency.
The distinguishing features of watercolor are its transparent binder and finely ground pigments. Together, these characteristics allow the paper support to show through the water-diluted paint, becoming the source of whiteness and luminosity in the painting. Darker areas of a composition can be built up in thin washes instead of a single, dark layer of pigment.
Accomplished watercolorists include Winslow Homer, Charles Burchfield, and Andrew Wyeth.