Watercolor Painting Mediums
Generally, watercolors are mixed with water for creating transparencies, but mediums such as gum arabic or premixed watercolor medium can increase the brilliance of colors. There are also several different mediums available to increase the fluidity, sheen and texture of watercolors.
Adding a medium to watercolors will ensure that the color is not over-thinned. Gum arabic increases brilliance, gloss and transparency and is the most commonly used medium. Ox gall improves wetting; adding it to a wash improves the flow on hard sized papers. Winsor & Newton Aquapasto provides watercolors with a texture which can be scratched out or thickens washes for use in lifting and moving color.
Art masking fluid and liquid frisket are not strictly mediums but allow the masking out of areas within a wash.