Watercolour paint consists of finely ground powdered pigments suspended in a water-soluble binder. Water is mixed with the paint during application. When water evaporates, the binder fixes the pigments to the surface, usually paper. The binder is made up of gum (e.g., gum arabic or dextrin), glucose, glycerine, brightener, fillers, and wetting agents. Glucose and glycerine slow drying time and make the pigments easier to dissolve. Brightener enhances colour and textures. Fillers help pigments adhere to surfaces.
Dried watercolour paint is not water-resistant nor permanent; it bleeds and lifts when layered or rewetted. Workable fixative may be used sparingly to secure under layers, but this method is not without controversy.
Watercolours are sold in blocks or tubes. The paint can be applied wet-on-wet and wet-on-dry for different effects. The main difference between watercolour and other heavy media is transparency. The whites in oils and acrylics are created by adding opaque white paint. The whites in watercolours are achieved by exposing the white of the paper. Apart from paper, watercolour paint also adheres to certain plastic, vellum, leather, fabric, and specially primed canvas.