Finishes are applied to woods for two reasons, first, that the wood may be protected and, second, that its appearance maybe bettered.

Of the materials used the following are the chief ones: Stain, filler, wax, varnishes, oil, and paint. These may be used singly or in combinations one with another or others in finishing.

Stains are used to give color to close grained woods. They are also used upon coarse grained woods before the application of a relatively darker filler.

Varnishes are of two kinds: spirit or alcohol and copal or oil varnish. The former, because of its rapid drying qualities is used mostly in manual training schools where dust abounds and no special finishing room free of dust and of even temperature is available.

Shellac or spirit varnish is a solution of lac and alcohol. Lac is soluble in both grain and wood alcohol but grain alcohol is preferable. Beds of crude lac are found in parts of Africa and South America where the lac has been left by the decay of leaves and twigs which it at one time encrusted. Crude lac is deposited upon leaves and twigs of certain of the lac-bearing trees by countless numbers of insects which draw out the sap.

Stick-lac is crude lac which has been purified somewhat of the bodies and eggs of the insects and rolled into stick forms. When crushed and washed it is known as seed-lac. When fully purified, which is done by melting and straining, it is spread out and is known as shellac.

White shellac is obtained by bleaching. Orange shellac is unbleached. Pure white shellac is used where the more yellow shellac would discolor. Orange shellac is stronger than white and will last longer but is harder to apply because it sets more rapidly.

Shellac varnish sets quickly, dries hard, but softens under moisture. Unlike oil varnish, it does not "level up" and must, therefore, be brushed on quickly, using long, even strokes. No spots must be omitted for they cannot be "touched up."

Most of the above finishes are applied with a brush. The best brushes are made from bristles of the wild boar of Russia and China and are expensive. They should be well cared for, being cleaned when not in constant use. Brushes which have been used in filler, or paint, or oil varnish are cleansed with turpentine, or kerosene, or gasoline, or benzine. Brushes which have been used in shellac are cleansed with alcohol. Brushes which are used from day to day should be kept suspended over night in the liquid being used, so that their bristles shall not touch the bottom of the bucket, otherwise they lose their shape, Fig. 123.

Fig. 123. Brush Holder

Fig. 123. Brush Holder.

Alcohol evaporates rapidly; shellac, therefore, should be kept in a receptacle which may have a top placed over it when not in use. White shellac is used for finishing light colored woods. It should be kept in a glass or stone jar, otherwise the metal will cause it to discolor.