WAX FINISH AND PAINTING Instead of varnish, wax is often used for finishing natural or stained wood surfaces. This is one of the oldest methods of wood finishing. The material used was formerly beeswax dissolved, with the aid of heat, in turpentine, or simply the plain pow dered wax, spread with the aid of weighted brushes. Both methods are still used, especially in the finishing of hardwood floors, but the commoner modern practice is to use prepared waxes, consisting of several kinds of wax with a small propor tion of a volatile solvent. This treatment produces a dull finish, which becomes lustrous with rubbing. The usual undercoat for wax is shellac varnish. No special skill is required to produce this finish, vigorous rubbing being the chief essential. The same effect is produced in more permanent form by the so-called "hard wax finishes," containing carnauba or other hard waxes.
While not usually classified as a method of wood-finishing, painting is more commonly practised than any other method. In the methods just considered the purpose is to enhance the natural beauty of the wood itself, whereas paint is applied for the pur pose of concealing the wood. Other types of finishing require that the wood shall be uniform in colour and free from defects and blemishes, but as paint (like enamel, already considered) per manently hides the surface, no selection is necessary.
Preparation for painting is essentially the same as for the types of finishing already discussed. The surface is sandpapered ; open grain woods are filled with paste filler coloured with the paint to be used; nail holes, cracks, etc., are stopped with putty similarly coloured ; the surface is again sandpapered ; and finally all resinous spots and knots are coated with a shellac varnish. The first or "priming" coat is then applied. This coat usually contains some what more oil and more volatile "thinner" (turpentine or mineral spirit) than the succeeding coats, to facilitate penetration and assure firm adhesion. The second coat contains less oil and less volatile "thinner" than the priming coat ; and the third, which is usually the finishing coat, less "thinner" than the second coat.
The methods of decoration with paint are of infinite variety, depending upon the taste, skill and ingenuity of the craftsman, since the hues, tints and shades at his disposal are practically unlimited and the possible combinations countless.
Various chemicals which in reacting with the chemical com ponents of the various woods produce colour changes of greater or less intensity are occasionally used by wood finishers, though to a less extent than formerly. The most popular of these is the treatment known as "fuming." It consisted formerly of prolonged exposure of the wood—chiefly oak or mahogany—to the fumes evolved from strong ammonia. It is now commonly brushed on the surface, but the older process yields more uniform effects. Other chemical stains with which varied effects may be produced on different woods are tannic, pyrogallic, chromic, picric, acetic, nitric, hydrochloric and sulphuric acids, the alkalis, potassium bi chromate, potassium permanganate, copper sulphate (blue vitriol), ferrous sulphate (green vitriol), ferric chloride, chrome alum and manganese sulphate. These chemical agents all have the advan tage of producing permanent coloration, in contradistinction to many of the commonly used dyes. Wood treated in this way is finished as with ordinary stains.
Various effects are produced by first applying ground coats of • flat paint or enamel, and after this foundation is dry applying a coat of transparent glaze of a different colour and while still wet stippling, wiping with a rag in various patterns, imitating graining with brushes and a whisk broom, etc. The effect known as "an tiquing" is produced in a similar manner, by applying over the flat ground coats a semi-transparent glaze coat of somewhat darker tone. Raw umber or a mixture of raw and burnt umber is com monly used. While the glaze is still wet it is wiped off with a soft rag. Sufficient colour remains to give the "antique" effect desired. The "old ivory" effect is produced by adding to white paint a little raw sienna and burnt umber for the ground coats and after these are dry glazing with a thin mixture of the raw sienna and burnt umber. Ebony is simulated by painting first with vermilion (Japan colour) and finishing with two or three coats of black tinted with Chinese blue. All these special finishes should be pro tected with one or two coats of varnish.
The first type, used to replace varnish in the finishing of fur niture and similar industrial products, is applied to surfaces already stained, filled and otherwise prepared in practically the same way as for finishing with varnish. The lacquer coating hardens within a few minutes. Two or three coats are usually applied, the final coat being rubbed as in finishing with varnish. Pigmented spraying lacquers are most largely used for finishing automobiles, railway coaches and similar products. The rate of drying is somewhat slower than that of the clear lacquer, but still quite rapid. Two or more coats are applied, with or without rubbing according to the finish desired.
Brushing lacquers were devised for domestic use. They are pigmented, like the coloured spraying lacquers, but the speed of drying has been retarded so as to permit application with a brush. They are, nevertheless, completely hard within about 3o minutes. They are "flowed" from the brush and cannot be worked over like varnish. The technique is different, but easy to acquire, and the results are novel and both beautiful and enduring.
Still more recently, to meet the competition of lacquer and to overcome some of its disadvantages, the quick-drying oil var nishes known as "four hour varnishes" have been developed. They are, to all intents and purposes, oil varnishes in which certain synthetic resins have been substituted for the fossil resins com monly employed.
See PAINTS, CHEMISTRY OF; VARNISH; GILDING; ENAMEL; LACQUER ; DECORATIVE ART.