One of the attendant drawbacks of houses that are newly built, or have been hastily finished for letting, is the inferior painting of the woodwork, and its speedy destruction. The wood is not thoroughly dry, and the consequence is the preparatory coat does not adhere; the pores being full of dampness, it is impossible for the oil to sink into them, especially as oil and water are unmiscible. Another equally injurious condition is the gum-resin which exudes from the knots of new pine and other timber. Painted over before it has time to come to the surface, the coat is destroyed by the action of the gum. Now, these cvils have to be endured so long as the wood has no time to get seasoned. The painter follows the carpenter without any interval of time, and before the action of the weather can bring out the moisture and resinous substances. A coating of shellac is usually given to the knots, though this is often so thin as to be worthless. Crude petroleum, as a preservative coat, is found to be an admirable preparation for the painting. The petroleum is thin, and penetrates the wood, filling up the pores, and giving a good ground for the coats of paint. According to one American authority, the preparation is of great value.
The priming coat should be thin and well rubbed in, and it is better to use a darker colour than white-lead as a base. White-lead forms a dense covering to the surface, though it has its disadvantages. When petroleum has formed the first coat, two other coats will suffice, one being the priming coat, and a third coat may be given after the work has stood for a season. It is a very desirable plan to leave the painting, or rather finishing coats, for a time, so that any imperfections in the wood or work may be discovered; it also allows time for any change of colour that may be made. After the priming coat, it is usual in good work to stop all cracks, nail-holes, and other defects with putty; but in the commoner class of paintings, the coats are laid on quickly; the preceding coat has hardly time to dry before the next is put on, and all the defects of wood, bad seasoning, exudation of gum, etc, quickly begin to show themselves through and disfigure the work. A good paint ought to possess body power of covering up, of flowing evenly from the brush, and become hard. Though zinc-white has less body than white-lead, it is more durable, and will stand sulphur adds without blackening.
Some colours stand better than others; the ochres, Indian and Venetian reds, burnt and raw umber are reliable, and may be used without scruple. It is also worthy of notice that salt air acts injuriously on white-lead, and zinc-white is therefore preferable in situations exposed to the sea-air. (Eng. Mech.)