Watercolours (UK), also called watercolor (US) or aquarelle (French), are paintings whose colours are water-based pigments. These are coloured materials gained from earths, rocks, plants, or chemicals, dissolved in water and then dried into a powder in the form of cakes or tablets. When water is added, the powdered pigment becomes liquid again. The pigment is applied to white paper or white card by brush or cloth or cotton wool, and allowed to dry. Unlike painting in oil-based pigments (coloured materials dissolved in oil), a watercolour cannot be painted over without spoiling the colour, whose purity depends on the white backing below. Therefore each area of a watercolour painting is painted only once, without alteration, and appears fresh and original rather than worked over. Watercolour painting is often used in Chinese, Korean, and Japanese paintings. Fingerpainting with watercolours came from China.