This section is from the book "A Treatise On Architecture And Building Construction Vol4: Plumbing And Gas-Fitting, Heating And Ventilation, Painting And Decorating, Estimating And Calculating Quantities", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
Black And Gold Marble. The ground being black, paint the large spots, from which the fibrous veins are to run, with yellow ocher and white, whose brightness must be heightened by the addition of a little vermilion. The masses must be dabbed with freedom upon the ground, with a brush full of color, and, while quite wet, threads drawn from them in all directions, some, of course, larger and thicker than others. White veins, with small threads attached, crossing each other and the yellow veins in all directions, are sometimes seen running in the deepest parts of the black. Care must be taken that the threads are connected with, and run in the same direction as, the thicker veins. If the ground is properly prepared, the yellow and white veins may both be painted at once in oil color. In cabinetwork, most beautiful imitations of the finest specimens of this marble are produced by spreading a leaf or two of gold in any part of the work where gold and silver leaf, and where white veins, are intended to run. The black ground is then to be rather thickly painted over the whole surface, covering the gold and silver leaf. After the color has been on a short time, take a round, pointed bodkin, or similar instrument, and draw this color in small, reticulated veins, from off the gold and silver leaf. The metal then shows in fine lines. The larger masses are to be wiped off with the wash leather over the point of the thumb or a piece of wood. When the black is dry, the yellow and white veins are to be painted as before directed, and drawn over the gold and silver, which by this means will, with great brilliancy, show through them. Otherwise, paint the ground in deep ivory black; put on the veins in white, yellow ocher, burnt and raw sienna, using a camel's-hair brush; glaze the spaces between the veins with a thin coat of gray, or white, over which pass a few white veins. The veins may also be put in with gold leaf.
Porphyry. Mix the ground color of Venetian red with a little vermilion and white until the required tint is obtained. The first layer of spots is produced by sprinkling in the following manner: Mix some of the ground color with a larger quantity of white, in a paint pot, and use a large brush well worked in the color; hold the palette knife over the paint pot, and brush the hairs of the brush against the edge, so that as much as possible of the color may be forced out of it; then, taking the handle of the brush between the palms of the hands, roll it to and fro with a rapid motion, the ends of the hairs being below the level of the top of the paint pot, but not touching the paint. This is called wringing out the brush, whereby a further quantity of the paint may be discharged; now hold a stick in front of the work and strike the handle of the brush against it; the color that may still remain will thus fall on the surface in a variety of small dots. Great care on the part of the painter is at this stage demanded, so as to distribute the spots equally; otherwise, while one part of the work may be left only partially spotted, others are so thickly covered that the drops will run together and form blotches. When this work is sufficiently dry, the sprinklings may be repeated by dipping the brush into a color rather deeper than the ground. It may be Indian red, with sufficient white to give it a body. The sprinkling with this color must be done very sparingly, and rather more freely in some parts than others.
The last sprinkling is to be done with a clean, small tool, dipped in white paint only; the spots to be very fine. As much color, therefore, as possible should be previously removed from the brush; when it is found that so little color remains in the brush that although it will scarcely mark a board when rubbed on it, there will still be enough to produce the fine dots. In imitating some specimens, the three layers of spots are put on, and, in addition, a narrow opaque white vein is run among the spots, from which transparent threads are in turn drawn in various directions. These cannot be added until the whole of the sprinkling is quite dry and hard, and must then be formed with a sable pencil, hard threads being drawn out with a feather.