TEMPERA, the name given to the painting processes in which the medium employed is an albuminous, gelatinous or colloidal material. Practically, this is equivalent to saying that any painting process in which a vehicle, or binding material, other than oil is employed is tempera.
Yolk of egg, either alone or with the addition of a little vinegar, was the vehicle most generally used, but many other substances were also employed. Among them were the liquid obtained by boiling parchment or the skins of animals in water, which is practically the same thing as using glue. Pliny mentions the use of milk as a medium.
In more modern times it was the medium of the Italian Primitives. Cimabue learnt it from the Greeks, or so says Vasari, and Giotto, Fillipo, Lippi, Ghirlandajo, Botticelli and many others used it for their inspired works. Raphael, Titian and Tintoretto probably used it, at least for under-painting. In northern Europe tempera was earlier supplanted by oil than in Italy, but many of the Flemish and German Primitives employed it.
The panel was then covered with old linen cloth held in position by more size. On this surface the gesso grasso, or heavy plaster of Paris, ground in size, was spread with a spatula. The gesso sottile or final ground, composed of thoroughly slaked plaster of Paris mixed with size was then applied with a brush.
Devotees of tempera painting as practised by the Italians are convinced, not only of its great permanency, but of its peculiar charm. To quote Miss Herringham, the translator of Cennini:
"There is no doubt that while fresco and tempera produce a deco rated space in itself pleasant and figures and other objects can be suggested in slight chiaroscuro (q.v.) without appearing unfinished or crude, this is not the case in oil painting, which seems incap able of giving that pleasantness to the surface of a wall and re quires a completeness in values, tones and tactile qualities which makes the spectator look into the picture and forget the surface. Therefore the one art is monumental, where the surface must not be forgotton or obliterated and the other on the whole appears op posed to monumental painting." Roger E. Fry, writing in the Burlington Magazine of the charm of classic tempera says : "One may sum up the whole question of tempera as a medium by saying that, while it is more difficult than in oil painting to produce any effect at all, it is yet more difficult, almost impossible indeed, to produce with tempera those thoroughly ugly and uninviting surfaces which it requires pro- found science to avoid in the clayey mixtures of oil paint. Noth ing would be likely to have a more restraining and sobering in fluence on our art than the substitution of tempera for oils as the ordinary medium of artistic expression." Modern Uses.—Egg tempera, the medium to which both of these laudatory comments apply, is doubtless a most charming medium and an exceedingly permanent one, as demonstrated by the apparently magnificent preservation of many specimens of very great antiquity. It does, however, as Fry points out, present many technical difficulties, principally because of its exceedingly rapid drying. "Transitions of colour" says Fry, "must be made by hatched strokes or else by continual laying one thin coat over another until the transition is produced." This was the practice of the early Italians. In these days of "ready mixed" colours, procurable anywhere, there is not much occasion for the keeping alive of the ancient practices. Occasionally, however, an artist uses them successfully for current work.