A substance mixed with pigment, it holds raw pigment in such a way that it becomes workable in a painting medium. Its purpose is to weld the pigment granules into some sort of shape---liquid, semi-liquid or solid---where brush, knife or hands can carry the color to the canvas or paper. In oil paint, raw pigment is usually combined with a linseed oil binder to form a fluid paint. Watercolor's binder is gum Arabic, and pastel is bound with gum tragacanth. Joe Singer writes in his book, "How to Paint Portraits in Pastel" that 'it is often the binder and not the pigment that is the main cause for the deterioration of paintings, especially oil.' Source: Roger Dunbier, PhD, Unpublished essay on Mediums. <br><br>The nonvolatile adhesive liquid portion of a paint that attaches pigment particles and the paint film as a whole to the support.<br><br>That which holds the paint together, such as linseed oil for oil painting, polymers for acrylics, gum arabic for watercolors and gouache.<br><br>The ingredient in the vehicle of a paint which adheres the pigment particles to one another and to the ground. It creates uniform consistency, solidity, and cohesion.Also see adhesive, adobe, mortar and pestle, polymer clay, and solvent.