A natural sponge is a marvellous, and perhaps essential, addition to a basic set of watercolour painting materials. It is ideal for creating mottled or speckled textures, for the patina of granite rocks, fine foliage, or multiple flowerheads. To use, moisten the sponge in water to soften it and squeeze the water out fully. Mix up plenty of creamy paint on the palette (and I mean plenty because the sponge is greedy), and then dab the sponge in the paint and onto the paper, turning the sponge as you go to avoid any repetitive patterning. Colours can be applied in several layers both wet-into-wet or wet-on-dry. But even more useful is that the soft rubbing motion of a natural sponge can be used to lift and remove patches of paint more quickly and effectively than with a brush. On thick paper you can actually rub quite vigorously, I have lifted staining colours to quite an extent by allowing the paper to dry thoroughly in between repeated rubbing, and as soon surface of the paper shows signs of scuffing, I stop! Use a stencil to protect areas you do not wish to erase.