Opposed to glazing, which admits the presence of a transparent medium, scumble means an opaque coating. The technique remains similar, though (intermediating painted surface and public's eye).
Both scumbling and glazing are part of what is generally known as "indirect painting". In other words, the artist looks for an elaborate creation process involving multiple layers of paint added to obtain a complex and modified painting. Indirect painting has been approached by reputed painters like Van Eyck, Rembrandt, El Greco or, closer to our times, Modigliani, Soutine, Paul Klee and Braque.
Using the scumbling technique, the artist doesn't mean to conceal the paint underneath, but only to change its effect. However, scumbling is different in that it involves applying a semi-opaque paint over a darker color. Most indicated combinations are those using Naples yellow and opaque white over dark shades. Most common result is pearled opalescence, but there the painting can also enhance a smooth smoky effect.
Consequences of scumbling include, as well, accentuated brush marks and support irregularities in the layers beneath. Therefore, the artist tries to add essence and meaning to the underpainting, as early layers of paint are called. Scumbling is correctly proceeded only on completely dry underpainting. In case scumbling doesn't result into the targeted effect, paint can be removed while still fresh and wet with the help of a soft, clean and moistened textile, dipped into turpentine or not.
Help me improve this site: Send me your feedback. Thank You.