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.
Umbers, natural pigments consisting of a mixture of clays and brown hematite, are valuable on account of their transparency and of their good drying qualities when in oil; the latter qualities are so pronounced that umbers may be employed as drying agents. Raw umber is unsurpassed as a graining color for light imitations, whilst burnt umber may be used for antique oaks from light to the darkest. In mixing grounds, also, umbers are invaluable. Raw umber does not injure colors with which it is mixed. Burnt umber is very permanent, and is sometimes used instead of Vandyke brown.
Raw sienna is the yellow pigment used for very rich and light oak, but, properly, should seldom be required, as decided yellow and bright tones are not characteristics of real oak. The siennas are used in oak colors to produce a forced richness. Similar in nature and preparation to the umbers, they are more transparent, but lack the natural drying qualities of umber when used in oil. Siennas are used to produce those imitations which are obtained by the use of pigments ground in water; they are useful for graining in mahogany, maple and walnut. Raw sienna is rather an impure yellow, but has more body than the ochres and is also more transparent. By burning it becomes burnt sienna, which has similar properties. Burnt sienna is a rich, transparent and red-brown pigment; gold size may be used as a drier with it. It dries better than raw sienna, and is very
