Practical hints for furniture men

Finishing is the process of applying to the surface of wood a thin coating of varnish or other substance, to render it durable, enhance its beauty or change its appearance. There are numerous methods of finishing, and a variety of materials are used; the varieties of varnish being the principal. The distinctive qualities of these varieties are treated under the article Varnlshes.

In their natural state all woods are more or less porous, consisting of bundles of hard fibres, with interstices filled with a softer substance. These constitute the grain, and as the hard or soft parts predominate the wood is said to be hard, fine, or close-grained, or soft and open-grained. To fill these softer parts, or pores, and give to the whole an even, uniform surface, hard, and capable of a brilliant polish, is the object of the finishers' art. This hard, firm surface was formerly gained by the successive application of several coats of varnish, at least three preliminary coats being required to fill the pores; the inequalities were then reduced by fine sand or glass-paper, and several additional coats laid on, the last, after becoming thoroughly hard, being polished if desired. In this operation, however, a great quantity of varnish is absorbed by the open pores of the wood, and it is consequently so expensive that it is now seldom used. Recourse is therefore had to various plans to render the wood non-absorbent before applying varnishes, and certain compounds called fillers are largely used for this purpose.

The Processes. - Finishing, although comprehending many minute sub-divisions, may be divided into four principal processes, i.c, Filling, Varnishing, Rubbing, and Flowing, Polishing, &c. Each of them are treated at length in their proper order, and for full information regarding the successive operations, the learner must refer to these heads: here we shall give a general view of the entire operation without details. The process described is tor fine work. First make the article to be finished quite clean and free from dust; then apply the proper filler with a brush; rub it well into the grain with excelsior or tow, rubbing across the grain when practicable, then clean all the surplus filler from the surface]with rags; after filling, allow the article to stand for several hours, during which time the filler should become quite hard and dry. Before proceeding to apply the varnish, if necessary, make the surface of the filler quite smooth, with sand-paper; then apply a coat of varnish, allowing it to get quite hard; after the last coat of varnish, with fine sand-paper, sand-paper the surface sufficiently to make it entirely .smooth and remove any lumps or irregularities. The number of coats required depends greatly upon the quality of filler used, regarding which some remarks will be found under the head of Fillers. It is said that with some fillers one coat of varnish is sufficient, but this can scarcely be the case with fine work, as it is not possible for one coat of varnish to give sufficient body to rub; four, or possibly three coats are more desirable. When the last coat of varnish has been applied, the article is ready for "rubbing" with pumice stone, moistened with linseed oil and applied with a bit of hair-cloth or coarse rag. This is for the purpose of making the varnish perfectly smooth and preparing it for the polishing. After rubbing, if a dead finish is desired, the work is complete, but the body of the work is generally cleaned up with a little oil well rubbed in, which gives it a lustre, afterward rubbed with a cloth dampened with alcohol which removes the surplus oil from the surface. The veneered panels are either "flowed" or "polished," which processes are described under these heads.


FILLING.

Fillers - These compounds play a very important part in the art of finishing, not only in the great economy of material and time required, but in producing a handsomer and more durable finish than possible, except at great cost, without them. Oil is sometimes used as a filler, but its use is not recommended; applied directly to the wood its effect is to swell the fibres, or "raise the grain," which remains in that condition until the oil becomes entirely dry, or disappears. During all this time the fibres are gradually shrinking, and consequently moving or checking the varnish. The qualities essential to a good filler are: that it shall readily enter the porous portion of the wood, and shall very soon harden and render the wood impervious to the varnish, which should lie smoothly upon the surface, giving brilliancy and effect to the natural beauty of the wood; that it shall not raise the grain of the wood; that it shall not change the color of the wood. These conditions are satisfactorily filled by very few of the home-made fillers ordinarily used in shops, and while we give a number of receipts, our readers are advised that they will obtain better satisfaction, at less cost, by purchasing some of the patent fillers now coming into general use, of which we can recommend the very excellent fillers of the Bridgeport Wood Finishing Co., New York, and J. W. Kenna & Co., Chicago. In these fillers very little oil is used and a large amount of dryers, so that the wood becomes perfectly dry and hard in a few hours, preventing any swelling or shrinking of the fibres of the wood after the varnish is applied. The following fillers should be allowed to di-y until quite hard. About eight hours are usually sufficient.


APPLICATION OF VARNISHES.

Preliminary to applying the varnish the pores of the wood should be filled, according to instructions given in the preceding receipts. Sufficient time should be allowed for the filler to become perfectly hard, and if any lumps or inequalities remain, the surface should be made perfectly smooth by the use of glass paper. All dust, specks, etc., should be carefully removed by the brush made for that purpose, and the work is then ready for the varnish.

Varnishes of all kinds should be uniformly applied, in very thin coats, sparingly upon the edges and angles, where the varnish is liable to accumulate. In first placing the brush on the surface, it should be applied, not close to the edge, which would be liable to give too thick a coat at that part, but at a little distance from the edge, and the strokes of the brush should be directed towards the ends alternately, with steady rapid strokes, and only very moderate pressure. If the surface is small, the whole may be passed over in one operation, and then the brush may be returned to the edge at which work was begun, and it may be passed over the surface a second or a third time, to distribute the varnish uniformly, and work out the air bubbles. Sometimes, in small surfaces, the second series of strokes is made at right angles to the first, in order to distribute the varnish more equally, and the third is laid on in the same direction as the first; but unless this is done expeditiously and equally, it leaves cross-lines, which injure the appearance of the work.

Large surfaces are more difficult, as the varnish thickens too rapidly to allow of the entire surface being covered at one operation. They must therefore either be worked gradually from the one edge to the other, as in lading a tint of water-color, or the varnish must be applied upon separate portions successively; but it is rather difficult to join the portions without leaving irregular marks. It may, however, be successfully accomplished by thinning off the edge with light strokes of the brush made in the same direction as those on the finished portion; but some care is required to avoid disturbing the former coat while it is still soft and easily acted upon by the fresh varnish. In the same manner, in laying on a second or any subsequent coat of varnish, care must be taken not to continue the application of the brush sufficiently long to disturb the previous coat, which is speedily softened by the fresh varnish; and if the application of the brush were continued too long, the preceding coat would be disturbed, giving to the work an irregular or chilled appearance. A sufficient interval of time should be allowed between each coat for the perfect evaporation of the solvent, whether alcohol, turpentine or oil. The time required for this depends partly upon the kind of varnish employed, and partly on the state of the atmosphere. Under ordinary circumstancss, spirit varnishes generally require from two to three hours between every coat; turpentine varnishes mostly require six or eight hours; and oil varnishes still longer - sometimes as much as twenty-four hours. But whatever time may be required, the second layer should never be added until the first is permanently hard; as when one layer is defended from the air by a second, its drying is almost stopped, and it remains soft and adhesive. In applying spirit varnish, some little tact and expedition are necessary, in order to spread the varnish uniformly over the surface before it becomes too much thickened by evaporation, or it will exhibit a very irregular surface when finished. If the surface does not exceed a few inches square, no material difficulty is experienced, as the whole may be brushed over two or three times before the varnish becomes too thick; but surfaces containing two or three square feet present much greater difficulty, as it is necessary that the varnish should be sufficiently worked with the brush to exclude all minute air-bubbles, which would spoil the appearance of the work, and can seldom be entirely removed until just before the varnish is becoming to thick to flow or spread uniformly after the brush has passed over it.