Scumbling involves painting a transparent layer of color over an area of color that has already dried, so that the lower layer shows through the upper layer, creating a translucent effect. To stop the colors running into each other, the lower application of paint must be completely dry. The colors blend together on the paper at the points where the colored areas overlap. The light sections visually recede into the background, whereas the dark sections appear more prominent.
Both scumbling and washing help you create an impression of space. If you combine the two techniques in one painting, the effect will be more varied.
Paint a light red circle with well diluted red paint. Leave it to dry completely. Apply a second circle over it, offset from the center, in yellow. An orange area will appear at the point whether the colors meet.
You can also use the same color to produce tones of different strengths and intensity at the points where the layers overlap. The more layers of color overlapping one another there are, the more intense the color appears.
