Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/51

Rh passed off there will be found left the oil at the bottom of the saucer. Fresh spirit may be added, and the process repeated until there is enough oil to pour off.

Tar. The spirit of tar is in two shades, one a rich amber, the other a dark brown, but both are alike in nature. The oil of tar corresponds to it in the same way as the oil of turpentine does to the spirit of turpentine. The spirits of oil of tar are of similar use to the other spirit and oil, and are employed principally by those who object to the vapor of the turpentine as causing headache or affecting the throat. The spirits of turpentine and of tar are extremely volatile, the former being somewhat more so than the latter; and

during the working, sufficient may pass off to render the paint somewhat troublesome to deal with. This difficulty is, however, only a slight one, and is easily overcome by the use of a little

Oil of Lavender. Oil of spike, as it is sometimes called, is a perfectly volatile and fluid oil, but very much less volatile than either of the above mentioned spirits, and a small quantity is added to the other mediums used when it is desired to keep the work open, to counteract its drying or fattening through loss of spirit.

The mediums should be kept in bottles with closely fitting stoppers, especially the spirits, as otherwise these would quickly become "fat" by evaporation.