“By Scumbling is meant, the application of opaque tints very thinly, over parts that have already been painted, and that are sufficiently dry and firm, to undergo the operation; it is usually performed with a hog's hair brush, very sparingly charged with the tint to be employed; which is called a Scumble, and must be generally lighter, though nearly of the same tone of colour, as the part over which it is passed.
"Scumbling may with proper judgment, be used in any part of the picture, but it is better if possible to avoid using it over shadows, more particularly such as are wished to be kept transparent, and to confine its application chiefly to the lighter parts where it may be required.
"Its use is to weaken the force of colours that are too strong, and force themselves too much on the eye, for the preservation of harmonious effect; to give air and distance to objects that seem too near, and to soften and unite such tints on the surface of particular objects, as may be too violently contrasted for breadth of effect.
"A Scumble is generally a tint made of some colour mixed with white; its usual effect is to render the part of the picture where it is employed, somewhat cooler, grayer, and less defined than before; hence it is of great service in connecting any tendency to muddiness or dirtiness of colouring; and also to what is called hardness, or over-distinctness of detail.
"Scumbling, in its effects may be viewed as the opposite of Glazing; and if a picture has been injured by too free a use of the latter, it may, in a great degree be remedied by the former; indeed each is to a great extent, calculated to remedy any errors that may be committed in the use of the other; and their judicious combination in the same picture, is found to produce the greatest possible clearness, brilliancy, transparency and richness of colouring."
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Painting by William Logsdail. St. Martin in the Fields, courtesy Art Renewal Center. Second painting by F. Waugh.
Document courtesy Graydon Parrish. Title: The Guide to Oil Painting, page 41. Kownky, Dillon and Rowney, 51 Rathbone Place.