Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/414

406 brush. With care, paint will look well for a long time if guarded from the influence of the sun.

Painting, Effect of, on Wood. It is, of course, generally understood that the main purpose of painting wood is to preserve it from decay, but this effect is only to be expected when the wood is previously quite dry, if this is not the case, the painting is injurious instead of being beneficial to the timber. There is a cause which affects all wood most materially, which is the application of paint, tar, or pitch before the wood has been thoroughly dried. The nature of these bodies prevents all evaporation, and confines the internal moisture, which is the cause of sudden decay. Both oak and fir posts may be brought into a pre-mature state of decay, by their having been painted prior to a due evaporation of their moisture, and painting affords no protection to timber against dry rot. On the other hand, the doors, pews, and carved work of many old churches have never been painted, and yet are often found to be perfectly sound, after having existed for centuries. Painted floor-cloths are very injurious to wooden floors, and soon produce rottenness in the floors that are covered with them, as the painted cloth prevents the access of atmospheric air, and retains whatever dampness the boards may absorb, and therefore soon causes decay, carpets are not so injurious, but still assist in retarding free evaporation.

Putty, To make. Pulverize the required quantity of whiting, which has been specially dried, and pass through a sieve of about forty-five holes to the square inch, mix the powder with as much raw linseed oil as will form it into a stiff paste, which should be well kneaded and left for a day or so, it must then be worked up, a small quantity at a time, so that it may be rendered quite smooth, and that balls of the dry whiting powder may not be imprisoned in different parts of the putty, for these would make their appearance when the putty was being used, and would of course injure the adhesiveness of the composition. Putty