Oil Painting - Special Effects

One way to make flake white crisp and useful for sharply textured effects for under- or overpainting is to mix in a little egg yolk by working it into the point thoroughly with the palette knife. The egg yolk must be added a little at a time, until the desired manipulative properties are obtained, avoiding an excess which might produce tempera or water-soluble paint. For the same reason, neither turpentine nor water should be added during the mixing, although the paint may be freely diluted with turpentine during its use. This mixture is a dual emulsion in which oil is the surrounding medium or external phase, and it can be handled and thinned like any other opaque oil paint except that it dries or sets up more rapidly. It tends to dry to a mat and somewhat coarse finish.

Another means of achieving this crisp handling quality is to grind titanium or zinc white to paste consistency in whole egg and mix two parts of it thoroughly with two to three parts of flake white [p. 114] tube oil color. Some artists use an egg-and-oil tempera emulsion, such as the one mentioned on page 145, instead of straight egg; the entire procedure requires a little experimentation to suit the individualÍs personal requirements, and the resulting dried paint films have to be carefully examined to see whether or not they are tough and flexible enough before adopting any such mixture of materials for continual use, especially on canvas. Casein paints will also mix with oil colors in the same way, but the combination of casein and linseed oil is not recommended because of rapid after-yellowing and embrittlement of such mixtures on aging. Ready-made textural whites of this nature are sold in tubes under proprietary names; these are believed to be of synthetic-resin origin.

Throughout the nineteenth century a number of complex painting mediums were added to oil paints in order to alter their brushing qualities, and virtually all these have been discarded because of the rapid decay of the paintings in which they were used. Chief among these offenders was a jelly-like substance with a curious name, megilp. Made by mixing heavy mastic varnish with a linseed oil that had been cooked to blackness with litharge or white lead, this material was used with oil paints to impart a brushing quality that overcame many difficulties, at the almost certain cost of the eventual disintegration of the painting. History teaches us that the wisest course is to adhere to the simple oil paint technique as much as possible, to use oleoresinous painting mediums with restraint, and to avoid complex jelly mediums. [pp. 113-115]