6. Finishing Furniture

There are two general types of finishes, classified according to whether they are transparent or opaque. The transparent finishes, designed to bring out the natural beauty of the wood are oil, water, and spirit stains, rubbed oil and wax finishes, shel­lacs, varnishes, and clear lacquer. The opaque coat­ings include paint and lacquer enamels.

The most vital step in the finishing of furniture is the preparation of the wood surfaces. The wood is the foundation of the finish, and whether the finish is opaque or transparent, what lies under it will affect its character and reflect the degree of skill and care bestowed upon it.

In all newly made furniture, whether a copy of an old piece or the latest modern design, the basic treatment is the same. The wood must be smooth and free from rough grain, and all dust carefully wiped off before any finish is applied. The first stage in finishing any piece is the smoothing of the surface, and for this operation steel scrapers, sand­paper, and steel wool may be used.

Scraping

On certain woods, such as soft pines and cedar, it is sometimes advisable to smooth the surface after planing by scraping. The tool used is a flat piece of steel such as a piece, 5" x 2½ ", cut from a hand saw blade. The edge must be perfectly straight, and filed to a slight bevel, say 30 degrees, and smoothed on an oilstone. Then a cutting edge is formed on it by rubbing a piece of hard steel along the edge so that a burr is formed on one or both edges. The scraper is used by holding it firmly with both   hands,   bowing   it   slightly   outward   in   the center and pushing (and sometimes pulling) it along parallel to the grain of the wood. The corners of the scraper should be rounded off so that they will not accidentally dig into the wood or scratch the surface. Curved scrapers can be used for hollow and rounded surfaces and for work on mouldings.

Sanding

The best type of sandpaper for fine cabinet work is the garnet paper, and the most useful grits are (in order of increasing coarseness) the 4/0, 3/0, 00, and 1/2. The 6/0, wet-or-dry paper, dipped in water, is often used for smoothing between finish coats. Sandpaper is always applied along the grain in a straight forward and back motion.

For flat surfaces the paper may be wrapped around a wood block. This helps to avoid ridges and keeps the paper from rubbing off the arrises and rounding the edges. No block is used in sand­ing rounded surfaces, though rounds or half-rounds may help in cleaning up some interior curves and the insides of holes.

Working with Steel Wool

Pads of steel wool can be used to finish any wood surface, though flecks of metal are apt to become imbedded. It is, however, better reserved for smoothing after the application of filler or the first coating. The coarsest wool used for these purposes is the No. 1; and Nos. 0 and 00 are generally better for fine work. In all cases the steel wool is applied in the direction of the grain. If a coating of any kind has been applied it is necessary to use long, sweeping, light strokes so as not to generate appreciable heat in any one spot.

Raising the Grain

For an extra-smooth surface it sometimes pays to raise the grain by slightly dampening, and sand off the swollen fibers after the surface has thor­oughly dried.   In administering this treatment, the very small amount of moisture required is best applied with a damp (not wet) cloth. After drying, the raised fibers can be smoothed off with No. 000 garnet paper applied with the hand (not with a block). Moisture can be used also to eliminate small nicks and dents. A folded wet cloth is held over the damaged area and heat is applied by means of a soldering bit or flat-iron. The steam generated swells the crushed or cut fibers, which are then allowed thoroughly to dry. Light sanding completes the operation.

The surfaces are finally prepared for the applied finish by removing all traces of dust and grease. This is best done by wiping gently with a rag slightly dampened with turpentine. Excess glue should be gently scraped off during final sanding.

Filling the Grain

All wood is porous to some degree, and if the grain is open, as in the case of oak, chestnut, wal­nut, mahogany, and cherry, a much smoother sur­face is secured by applying a special filler. It is also much simpler and cheaper to use a commercial filler of powdered quartz than to load the pores with paint, shellac, varnish, or lacquer.

The filler can be used either before or after the wood has been stained. If done before, the filler should be colorless; if applied after the stain, it should be the same color as the stain.

Sometimes a contrasting filler is used to get special effects with transparent finishes.

The fillers, which are usually mixed with linseed oil and a thinner such as turpentine, benzine, or naphtha, may need still further thinning before ap­plication. The filler is worked into the pores with a stiff-bristled brush, and, when almost dry, the excess is wiped off with burlap, across the grain. When dry, this surface may be cleaned with a soft cloth along the grain. A day later the surface can be smoothed with 00 steel wool. Since there is oil in the filler, it is advisable in the case of light-colored woods to give them a wash coat of thin, white shellac. This will prevent the oil from darken­ing the grain. Some finishers also use shellac as a sealer after filling.

Stains

Of the three types of stain available, the oil stain is much the best in the hands of a novice. The water stains raise the grain, and both they and the spirit stains are quite difficult to apply without streaking.

The oil stain should be applied with a clean varnish brush, after testing the color on a piece of scrap wood of the kind used in the furniture. If a light finish is required, the stain can be wiped off after a minute or so. The longer it is left, the darker it will become, within limits. If the stain is too dark to begin with, it may be thinned with turpentine. Since end grain absorbs more stain it normally finishes darker. This can be checked by dampening it with clear turpentine before staining.

In staining horizontal grains it is usual to begin in the center and work toward the ends. For vertical grain, as in cabinet ends, start at the top and work down. Any recesses or inside angles should be done first, but do not let any part dry before completing the whole surface.

The use of a water stain calls for a preliminary dampening, drying and finish sanding of the wood to forestall any raising of the grain by the stain. To the novice it may be easier to apply the stain with a spray gun, though even that is not proof against unevenness. If a brush is used it should be a fairly large one, and the stain applied rapidly because it is so quickly absorbed by the wood. Excess stain would be wiped off each surface as it is completed, and any lap marks may be toned down by going over the whole surface with a dry brush. The excessive darkening of end grain can be controlled by dampening it first with water or lightly brushing with glue size. Most of the water stains need to be freshly mixed a short time before use, preferably in slightly warm water.

In spirit stains the solvent is alcohol, and the rapid evaporation makes it difficult to apply the color evenly. Otherwise the method of application is the same as for water stains, though no prelimi­nary dampening or sanding is necessary.

Clear Finishes

One of the most satisfactory finishes that does not change the natural color of the wood is white shellac. Afer filling the wood grain, if necessary, several coats of clear shellac are applied. The first coat needs to be thinned by adding ½ gal. alcohol to 1 gal. of 4-lb.-cut shellac. Succeeding coats should have less thinner, and the final one is the full 4-lb. strength. Three or four coats should be sufficient, with a light sanding with 006 garnet paper between applications. The surface can later be protected and given a pleasing deep gloss with a coat of wax, well rubbed.

Varnish will give an even richer finish than shel­lac though it may darken the wood a little. It takes more care and effort to do a varnishing job because of the length of time the surface remains soft and picks up dust. A dust-free room kept at a tempera­ture of about 70 degrees F. is the first requirement. Either a glossy or dull-finish varnish can be used. A dull finish can be given to a glossy varnish by rubbing with steel wool or pumice. The varnish can be used over a surface sealed with shellac, and each coat allowed to dry overnight. Some varnishes need 72 hours to dry. Before applying the next coat, always test the last one by pressing with the fingernail. If this makes an impression, the coat is not dry.

Between each coat rub down the varnish lightly with 6/0 garnet paper or 2/0 steel wool along the grain, and wipe off with a clean, soft rag. A final coat of wax can be applied if desired.

Lacquer forms an excellent transparent surface that will stand abuse, but it is best applied with a spray gun. Some slow-drying lacquers have been developed for brushing. They may or may not have solvents that enable them to be used over other finishes. Lacquer dries quickly and so is not so likely to pick up dust. Three coats should be ap­plied, and sanding is not necessary because one coat softens and unites with the coat underneath. Either glossy or flat lacquers can be procured to give any required finish.

Bleaching

To get a light finish on dark woods, or to remove dark streaks from light woods, a bleaching process is necessary. Streaks on light wood can often be touched up with a strong, hot solution of oxalic acid in water. The acid must then be ''killed" by applying an alkaline solution, such as soda or borax. For bleaching the dark woods a more powerful bleach is required. Such bleaches can be obtained from most paint stores with full directions for their use. All bleaches raise the grain, and should be followed by careful sanding.

Various types of blond finishes can be applied to the bleached wood. Most of them use a natural-color, or slightly tinted filler. A number of commer­cial finishes are available to simulate the transparent finishes on surfaces that have been finished in some other way. For example blond maple or limed oak can be simulated by applying first a ground color over which a graining compound is brushed, then wiped off with cheese cloth. The final coat is a clear lacquer.

Opaque Finishes

For finishes that hide the grain of the wood there is a wide choice of opaque lacquers, enamels, and paints. These can all either be left plain or decor­ated by stenciling, transfers (decalcomanias), or free-hand painted designs. The pigmented lacquers need to be sprayed, but enamels with synthetic bases can be brushed on. With enamels the best results are obtained by priming soft woods with thin shellac, and heavily grained woods with thinned varnish enamel or a special undercoater. For dark woods this undercoater can be tinted to the approxi­mate final color. Two coats of enamel are usually sufficient, with a light sanding between applications.

Toning and Antiquing

Light woods newly finished have a pristine air that sets them apart from older furntiure that they are used alongside. This "sore thumb" effect may not always be desirable and it sometimes helps to tone down the new finish. This is quite simple, par­ticularly on pieces that have a shellac finish. All that is required is a thin paint wash made up of about three parts burnt umber and one part burnt sienna, oil colors. These are well diluted in turpen­tine, with a few drops of japan drier added. This is mixed to a thin creamy consistency and brushed over the entire surface to be treated.

In a few minutes, when this coating shows signs of drying, almost all of it should be wiped off. The wiping must be carefully done, in the direction of the grain, using very soft rags with no hard folds or seams. If this is done properly, all the wood grain will be exposed, but the whole surface will have a soft warm tone. Highlight effects can be obtained by wiping over the edges and high spots a second time.

The finish should not be streaky, and if the first attempt is not successful, the paint can be wiped off, and a new attempt made.  This finish is left to dry for 72 hours, and can then be waxed as usual. If a hard wearing surface is needed, as in table tops, this toning can be varnished over in the regular way.  For furniture that is to be antiqued the same system  is  used,  but a  little  more  color  left on. The surface is then waxed with a wax darkened with some of the same paint mixture.

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