permanent, as it is not liable to change by the action of light and oxygen, or by damp and impure air.
Vandyke brown, a transparent earth pigment, is a very slow drier, and, if used in oil, requires to be diluted with a drying agent. It has a dark color, inclining to neither yellow nor red, but yet extremely rich and deep. In oak graining, it is generally ground in water, its color being warmer and richer than when used in oil. It is the principal pigment used in overgraining oak. It is a bog earth.
Neutral blacks and blues, previously mentioned, are also to some extent transparent. Blue-black in conjunction with Vandyke brown is largely used for overgraining oak. Black enters into the composition of the dark grounds for antique oak. The effects of transparent blues may be regarded by some grainers as questionable, but it must be remembered that richness of color in woods is only a matter of comparison and contrast, and, therefore, if instead, of forcing the color values by bright grounds, bright graining color and rich overgraining, some contrasting cool tones are introduced, it is possible to obtain more natural color variety and yet retain the subdued contrasts of the real oak. Prussian and indigo blues are vastly different when ground in water from what they are in oil; whilst the tints are considerably mellowed by the final coating of copal or oak varnish. The first stages of oak graining should be worked in subdued tones rather than in false bright ones, and any desirable enrichment should be left for the glazing and overgraining to accomplish in preference to struggling in the final phase to modify early faults.
Megilp is added to oil graining color to, ensure that the latter shall not spread when combed. In ordinary and cheap oak graining an excess of the drying agent is made to serve the purpose, but the megilp generally acknowledged to give the most satisfaction is a preparation of beeswax. A few ounces of pure wax is shredded and dissolved, by the application of heat, in linseed oil; add to the dissolved
