Gum Arabic is the binder for watercolour. It is also used as a medium to help keep diluted watercolours from sinking below absorbent surfaces. It slows down the drying time of the paint giving more time to work on wet on wet, it also controls spread. Gum Arabic gives a crisp appearance to watercolour edges, increases transparency and gloss, while Gum Arabic washes will have greater depth and appears more luminous than colour washes alone