After the vases had been made on the wheel, Dr. Birch writes, they were duly dried in the sun, and then painted; for it is evident that they could not have been painted while wet. The simplest and probably the most common, process was to color the entire vase black. The under part of the foot was left plain. When a pattern was added, the outline, faintly traced with a round point on the moist clay, was carefully followed by the painter. It was necessary for the artist to follow his sketch with great rapidity, since the clay rapidly absorbed the coloring matter, and the outline was required to be bold and continuous, each time that it was joined detracting from its merit. A finely-ground slip was next laid upon a brush, and the figures and ornaments were painted in. The whole was then covered with a very fine siliceous glaze, probably formed of soda and well-levigated sand. The vase was next sent to the furnace, and carefully baked. It was then returned to the workshop, where a workman or painter scratched in all the details with a pointed tool. The faces of female figures were colored white, with a thick coat of lime or chalk, and the eyes red. Parts of the drapery, the crests of helmets, and the _antyges_, or borders of shields, were colored with a crimson coat, consisting of an oxide of iron and lime, like a body color. In the second style of vases the figures are painted in a dark brown or black, of an unequal tone, on yellow ground, formed of a siliceous coating over the pale red clay of the vase. An improvement upon this style was the changing of the color of the figures by painting, or stopping out, all the ground of the vase in black, thus leaving the figures of the natural red of the clay, and the marking of the muscles and finer portions, as an outline, of bright brown. After the paint had dried, the slip, or the siliceous glaze, was laid over the vase, except the under part of the foot and the inside. The colors used were few and simple, and were evidently ground excessively fine, and made into a kind of slip. Of these colors the black was the most important and the most extensively used. Great difference has always existed as to the nature of this color. Vauquelin takes it to be a carbonaceous matter, such as plumbagine or black lead. The Duc de Luynes asserts it to be an oxide of iron. Of opaque colors, the most important and extensively used is the white, said by Brongniart to be a carbonate of lime or fine clay. Red and yellow are sparingly used. Blue and green are rarely found, and only on vases of the latest styles. The liquid employed for mixing the colors is supposed to have been water.