The best megilp, seldom, however, used for graining on account of the expense, is made from mastic varnish and boiled oil. To make it, pour the boiled oil into the varnish, and use the jelly formed by the mixture. As a hard and fast rule cannot be laid down for mixing graining colors, the proportions depending on the conditions under which the work is done, the colors should always be tested before use. The color should rub out cleanly, easily spread, and the lines left, by the comb should keep their place, not running into each other or settling down. A method of oak graining now seldom practiced consisted in first laying the markings in with a flat, square-edged fitch, dipped in a mixture of sweet oil and beeswax. When this was dry, the graining colors, made up with weak beer, were applied. When the work had thoroughly dried, the beeswax was carefully washed off with turpentine. Ordinary graining color is best made with about equal parts of oil and turpentine, to which is added paste driers, one-eighth of the whole bulk, with sufficient coloring matter.

The coloring pigments used as ingredients of all oak grounding and graining paints may be briefly classified as either opaque or transparent. Of the former class are the chromes, yellow ochres and Venetian red, which should be. used only in making stains for grounding paints. Raw and burnt sienna, or terra di sienna, raw and burnt Turkey umber and vandyke brown may be considered as being transparent, though the quality is possessed by them in a varying degree. They are sufficiently translucent to give due effect to any colored ground upon which they may be superimposed. For purposes of glazing and overgraining, ivory and blue-blacks and Prussian and indigo blue may be used, though the two latter are required seldom.

Prussian blue is a good working and staining color, and a quick drier. Venetian red is cheap but permanent, and must be procured ready ground in oil. It is useful for grounds.

Lemon and orange chromes, when of best quality, are chromates of lead. They are brilliant, have good body and covering power, and make good tints when mixed with white. When used in oil they must be protected by varnishing, especially if exposed to impure air, which in time will turn them black. The chromes destroy Prussian and some other blues. The yellow chromes are made in three shades; the fourth shade is the orange chrome, a deep rich color. The shades are varied by increasing the chromate for deep orange, and lessening it for the pale yellows. These colors are injured by damp and impure air, sulphur fumes and hydrogen, but the orange chrome is said to last better than orange oxide of lead.

Chrome of either middle or orange tint, may be useful to a slight extent in staining ground colors, when very bright and rich imitations are required. Generally, however, chrome conduces neither to good coloring nor to the attainment of a natural woody effect. The chrome-yellow tint sometimes forms a ground for light oak, whilst orange-red is used for medium oak.

White-lead, the basis of all graining grounds, is one of the most frequently used pigments, and also one of the most faulty. It is made by suspending rolls of ordinary thin sheet lead over malt vinegar or pyroligneous acid, in close vessels, the evaporation from the acid being kept up by a steam bath underneath. The lead is thus reduced to a white powder ready for being ground with linseed oil into a paste. White lead improves by keeping and for good work should be stocked for at least twelve months after purchase. Very pale and old linseed oil should be used in the thinning, otherwise it will probably soon discolor. It is, however, about the best pigment for preserving wood from the effects of the weather. Zinc white is an oxide of zinc. It does not discolor and is a very pure pigment. It is a substitute for white-lead, but is not so employed in the practice of graining.

Vermilion is used only in the most exceptional cases; it can be had as a fine dry powder, free from grit, and is a very brilliant color in oil. The best quality only is permanent, and that is a sulphuret of mercury. Chinese red, or vermilion, is of a deep crimson tone, but has bad covering power, and, unless well protected, will soon fade under the action of light and impure air.

Indigo possesses great body, and is a good glazing color. It is not very durable and is injured by impure air.

Ivory black is made by placing ivory dust in a covered crucible exposed to a great heat. An inferior color known as bone black is made by treating bones in a similar way. Ivory black, the deepest and purest of the blacks, being somewhat hard, requires very careful grinding, and unless ground very fine is useless. It is best ground in turpentine, and diluted for use with turpentine, gold size and a little varnish. In drying it will become dull, so that it should not be used unless it is afterwards to be varnished. If thinned down too much with turpentine it will not bind, so that when the varnish is applied it will rub off onto the rest of the work and spoil the whole. Ivory black, when purchased unground, resembles drops and is sometimes called drop black, but bone black is prepared in the same way.

The various ochres, Oxford, yellow and Italian, are used only in the composition of grounding paint, and never in graining color. Really, commercial yellow ochre is the only one of this class of pigment there is need to use, since the addition of a little Venetian red will give any warmer tint desired. This latter tint, a kind of burnt ochre, can alone be commended for obtaining warmth in grounds. Yellow ochre is not a very bright color; it is best purchased in tubes, otherwise it is not thoroughly ground. Ochre is an earth found in most countries, and is of all shades, from the warm yellow of the Oxford ochre to the pale straw yellow of the French earth. The ochres are not liable to change through any chemical action, and may therefore be considered permanent.