"open" a little longer, usually allowing, ample time to obtain the desired result. If, however, the worker is slow and hesitating, clove-oil is to be recommend in preference. It is seldom necessary to add thick oil. With the powder colors, however, the thick oil is most essential, and must be added in about equal quantity in bulk to amount of powder..
Mix with the palette knife until thoroughly in corpora ted, then thin with either lavender or spirits of turpentine, or even both. The exact quantity must be determined by experience. Just so much is required as to enable the painter to get over a specified surface before it dries ; and it is desirable as soon as this has been accomplished to dry immediately. Therefore the only gauge is good judgment, which can only be acquired by practice. The large the surface to covered, the longer must the color be kept from drying ; and the less expert usually require More oil than those who, accustomed to its use, can work expeditiously. It is not easy to give more definite directions as to quantity, as it so largely depends upon the dexterity of the painter.
Spirits of wine, or or alcohol, is indispensable for cleaning brushes, palette, knife, etc. Turpentine will answer for this purpose in lieu of alcohol, but it does not cleanse those articles so thro-
