BRUSH

device composed of natural or synthetic fibres set into a handle that is used for cleaning, grooming, polishing, writing, or painting. Brushes were used by man as early as the Paleolithic Period (began about 2,500,000 years ago) to apply pigment, as shown by the cave paintings of Altamira in Spain and the Prigord in France. In historical times the early Egyptians used brushes to create their elaborate tomb paintings, while the ancient Chinese employed the tip of a long-haired brush to make the many intricate characters of their writing, a practice continued in the Orient today. The type of material used to make a brush and its design are dictated by the intended use. Hog bristles, for example, have long been used for paintbrushes and art brushes because such animal fibres are flexible and resilient and display an excellent capacity for holding paint. Each individual bristle has a broad, sturdy base and a tapered tip that splits into several fine filaments. The hair of other animals such as horses, oxen, squirrels, and badgers is used in certain kinds of household and toilet brushes, as are various types of plant fibres, the most important of which are piassava obtained from a Brazilian palm and palmyra bassine derived from the palmyra palm of Africa and Sri Lanka. Such plant fibres are converted into brush material by soaking, beating, and drying. Cotton fibres also can be used for brush bristles. They are treated with acetic acid followed by diffusion of the acetylated product in acetone. The resulting solution is spun and projected through the tiny orifices of a device known as a spinnerette and allowed to solidify. Artificial brush fibres are most commonly made of nylon and polyethylene, though vinyl and steel wire are also used for certain applications. Nylon fibres are either tapered and split like hog bristles for use in paintbrushes or left untapered for making cleaning brushes, hair brushes, and toothbrushes. Polyethylene fibres, which are rather short and stumplike, are suitable for massage brushes. Brush bristles are joined to handles and backs of wood, plastic, or metal in several ways. Paintbrushes and art brushes are assembled in a metal cup that forms a mold for the desired brush shape. After the bristles are trimmed to size and bound together, they are transferred to a metal ferrule into which cement or a gum rubber solution is poured. When this adhesive has hardened, a handle is fastened to the ferrule. Many household and toilet brushes are produced by inserting tufts of fibres into holes drilled in brush backs.