This is the medium that, together with gelatine, acts as the binder for water colour pigment. Water colours also contain glycerine to keep them moist. The added advantage of Gum Arabic is that by adding a little to the water when mixing paint, gives additional body, making it less runny and easier to blend. It is particularly suitable for the kind of painting that is built up in small, separate brush strokes, as it prevents them flowing one into the other.