147.Wood Finishes.—Finishes are applied to wood surfaces (1) that the wood may be preserved, (2) that the appearance may be enhanced.
Finishing materials may be classed under one or the other of the following: Filler, stain, wax, varnish, oil, paint. These materials may be used singly upon a piece of wood or they may be combined in ""various ways to produce results desired.
148. Brushes.—Good brushes are made of bristles of the wild boar of Russia and China. These bristles are set in cement and are firmly bound by being wrapped with wire in round brushes or enclosed in metal in flat brushes.
A large brush, called a duster, is used for removing dust or loose dirt from the wood. Small brushes, used for tracing, usually have chiseled edges, Fig. 239.
Bristle brushes are expensive and should be well cared for. Brushes that have been used in shellac and are not soon to be used again should be cleaned by rinsing them thoroughly in a cup of alcohol.
This alcohol may be used later for thinning shellac. Varnish and paint brushes should be cleaned in turpentine. If they are to be laid away for some time, a strong soap suds, or lather made from some of the soap powders, should be well worked into the brush, after the preliminary cleansing. It should then be carefully pressed into proper shape and laid way flat on a shelf. When the brush is to be used again, it should first be washed out, to get rid of all the soap.
Brushes that are used from day to day should be kept suspended, when not in use, as in Pig.240, so that their bristles shall be kept moist, without their touching Warn- spac Since alcohol evaporates rapidly, shellac cans with cone tops should be used. Fig. 241 shows a can which is made double. Varnish is kept in the inner portion and water in the outer ring.
The cover fits over the inner can and into the water space, thus sealing the varnish air-tight but removing all danger of the cover's sticking to the sides of the can. The brush is suspended from the "cleaning wire" so that its bristles rest in the liquid.
If delicate woods are to be varnished, stone or glass jars would better be used to hold the liquid, as metal discolors it slightly.
149. General Directions for Using Brush.—(1) Hold the brush as in Fig. 242. (2) Dip the end of the brush in the liquid to about one-third the length of the bristles. (3) Wipe off the surplus liquid on the edge of the can, wiping both sides of the brush no more than is necessary to keep the liquid from dripping. A wire stretched across the can as in Fig. 243 provides a better wiping place for the dripping brush. In wiping the brush on the edge of the can, some of liquid is run" down the outside. (4) Using the end of the brush, apply the liquid near one end of the surface to be covered. (5) "Brush" in the direction of the grain. (6) Work towards and out over the end of the board, leveling the liquid to a smooth film of uniform thinness. The strokes should be "feathered", that is, the brush should be lowered gradually at the beginning of the sweep and raised gradually at the close, otherwise, ugly "laps" will result. The reason for working out over the ends rather than from them will appear with a little thought. (7) Now work toward the second end. The arrows, Fig. 244, show the general directions of the final or feathering strokes.
Edges are usually covered first and adjoining surfaces afterward.
It frequently happens that surplus liquid runs over a finished surface, especially when working near the arrises. This surplus can be "picked up" by wiping the brush up- on the wire of the bucket until the bristles are quite free of liquid, and giving the part affected a feathering sweep.
If the object has an internal corner, work from that out over the neighboring surfaces.
Panels and sunk places should be covered first. Afterward, the raised places, such as stiles, rails, etc., may be attended to. Wherever possible the work should be laid flat so that the liquid may be flowed on horizontally. This is of especial advantage in varnishing. Vertical work should always be begun at the top and carried downward.
Tracing consists in working a liquid up to a given line but not over it, such as painting the sash of a window. Tracing requires a steady hand and some practice. A small brush is generally used and the stroke is made as nearly continuous as the flow of the liquid will allow.
150. Fillers.—Fillers are of two kinds, paste and liquid. They are used to fill up the wood pores and thus give a smooth, level, non-absorbent surface, upon which other coverings may be placed. Paste fillers are for use upon coarse grained woods such as oak and chestnut, while liquid fillers are for close grained woods such as Georgia pine.
Fillers are not a necessity, especially the liquid, but the saving effected by their use is considerable. Not only are they cheaper than varnish but one or two coats of filler will take the place and permit a saving of two or three coats of the more expensive material.
Liquid filler should be applied evenly with a brush and allowed to dry twenty-four hours, after which it may be sanded smooth with No. oo paper. It is used mainly upon large work such as porch ceilings and interior finish, like Georgia pine. On fine cabinet work, one or two coats of thin white shellac is used as a filler upon close grained wood. Shellac forms a surface which, after twenty-four hours, can be sandpapered so as to make a very smooth surface. Varnish applied to the bare wood has a tendency to darken and discolor it. Filling with shellac preserves the natural color.
Paste filler is sold by the pound in cans of various sizes. The best fillers are made of ground rock crystal mixed with raw linseed oil, japan and turpentine.
For preserving the natural color of the wood, filler is left white; for Flemish, it is colored brown; for antique and weathered finishes, it is dark. Fillers can be purchased ready colored.
151. Filling with Paste Filler.—(1) Thin the filler with turpentine until it makes a thin paste. (2) With a stiff-bristled brush, force the filler into the pores of the wood and leave the surface covered with a thin coating. (3) Allow this to stand until the filler has "flatted," that is, until the "gloss" has disappeared and the filler becomes dull and chalkish. The time required for this to take place varies. Twenty minutes is not unusual. (4) Rub the filler off just as soon as it has flatted—do not let it stand longer, for the longer it stands the harder it is to remove. Rub across the grain as much as is possible, using a wad of excelsior. Finish fine work by going over it a second time with a cloth, rubbing with the grain as well as across, that the "high lights" may be clear of filler.
On fine work use a felt pad to rub the filler into the pores, and rub off with a cloth only.
Twenty-four hours should be allowed the filler to harden. One filling is sufficient for ordinary work; on fine work the above process is sometimes repeated after the first filling has hardened.
The striking contrasts in the grain of wood such as oak and chestnut, obtained by the use of colored fillers, are due to the dark filler's remaining in the open grain but being wiped off of the close grain—the "high lights."
On quarter-sawed oak, each flake is sometimes sanded with fine paper, No. oo, to remove the stain that the contrast may be sharper.
Excelsior and rags used in cleaning off filler must not be allowed to lie around, but must be burned, as they are subject to spontaneous combustion and are dangerous.
152. Stains.—Stains are used to darken the high lights of wood preparatory to the application of a relatively darker filler. By varying the intensity of the stain different results may be obtained with the same color of filler. Stains are also used without fillers.
There are three kinds of stains: (1) water, (2) oil, (3) spirit. Each kind has its advantages and its disadvantages.
Water stains are cheap, penetrate the wood deeply, and are transparent. They cause the grain of the wood to "rough up," however, and for this reason are used mainly upon hard woods which require darkening before the application of a filler. The wood is sanded before the filler is applied. Where water stain is not to be followed by filler, it is customary to thoroughly moisten the surface to be covered with water alone. After this has dried, the surface is sanded with fine paper and the stain applied. The stain does not raise the grain as it otherwise would.
Water stains may be applied with a brush or a sponge. They are sometimes heated that they may enter the wood more deeply. Any coloring matter that can be dissolved in water will make a wood dye or stain.
Oil stains, like water stains, are often used to stain wood before filling. They are more generally used where no filling is desired. They are easier to apply evenly than water or spirit stains. They do not raise the grain of the wood like the other stains. On the other hand, they do not penetrate and therefore cannot color hard woods dark. Neither do they give the clear effects.
Most oil stains are applied with a brush, after which the surface of the wood is immediately wiped clean with a cloth.
Spirit stains are but little used where surfaces of any size are to be covered. They are expensive, fade easily, and are hard to apply evenly.
They are applied with a brush and dry very quickly. A stain which penetrates deeply and is clear is obtained by placing the wood in a closed receptacle in which is placed a dish of concentrated ammonia. The fumes of this liquid cause a chemical change to take place, giving to the wood a rich nut-brown color.
153. Waxing.—An old finish that has recently become popular is that of waxing. It takes the place of the varnish, by which it was supplanted years ago.
Wax finish is easily applied and is cheaper than varnish. It will not stand wetting. However, it is easily repaired.
Our ancestors used to make wax polish by "cutting" beeswax with turpentine.
Rapid drying and hardening waxes can be purchased now-a-days. They require a smooth surface and a very thin application for a successful result. Too much wax upon a rough surface' will produce very ugly, white, chalk-like spottings as the wax dries. These are especially noticeable upon dark finishes. Waxes colored black overcome this but are not needed if the ordinary wax is properly applied.
In finishing with wax the following directions may be followed: (1) Stain the wood if a very dark finish is desired. (2) If the wood is coarse-grained, put on two coats of paste filler and rub it off carefully, that a smooth surface may be prepared. Allow the stain twelve hours in which to dry, also each coat of the filler. (3) With a soft cloth apply as thin a coating of wax as can be and yet cover the wood. Wax is in paste form. (4) Allow this to stand five or ten minutes, then rub briskly with a soft dry cloth to polish. (5) After this coat has stood for one hour another may be applied in the same manner.
A thin coat of shellac brushed evenly upon the hardened filler "brings out" the grain and makes an excellent base for wax as well as varnish. It should stand twenty-four hours and then be sanded smooth with No. 00 sandpaper before the wax is applied.
There are other patent preparations which give the same soft effects as wax and are as easily applied—in fact, some of them are but wax in liquid form.
154. Varnishes.—Varnishes are used where a hard, transparent coating is desired. There are two kinds, (1) shellac or spirit varnish, (2) copal or oil varnish.
Varnishes vary greatly in quality and therefore in price. If made of specially selected pale gum for use on light or white woods the price will be higher than for that of ordinary color tho the quality may be no higher.
Rubbing varnishes are so made that they may take a "rubbed finish."
Varnishing should be done in a room in which the temperature can be kept from 70 to 80 degrees Fahr., and which is comparatively free from dust. The surface to be covered must be clean, dry and filled even and smooth.
155.Shellac.—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 up on 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."
156.Shellac Finishes.—The use of one or more coats of shellac preparatory to a varnish finish has been noted.
A very simple finish, and one that is easily applied, is obtained by covering stained wood with a very thin coat of shellac.
To obtain the finish known as egg-shell gloss, (1) Coat the smooth wood with from three to six applications of thin shellac. Allow each coat twenty-four hours in which to harden. (2) Rub to a smooth surface each hardened coat, using curled hair or fine steel wool or fine oiled sandpaper.
157.Oil or Copal Varnishes.—Oil varnish is composed of copal gum, boiled oil and turpentine. Copal gums are obtained from Africa mainly, in certain parts of which they are found as fossil resins, the remains of forests which once covered the ground.
Pressed flaxseed furnishes crude linseed oil while the long leaf pine of the South furnishes the turpentine pitch.
The oil is prepared for use by boiling it in huge kettles with different materials which cause it to change chemically. It is then put away to settle and age, that is to clear and purify itself. It takes from one to six months for the oil to reach a proper degree of clearness and purity. Turpentine is obtained from its pitch by distillation.
The copal gums are melted and boiled thoroly with the oil. Turpentine is added after the mixture of gum and oil has cooled sufficiently. The whole is then strained several times, placed in tanks to age or ripen. Form one month to a year, or even more, is required.
The quality of varnish depends upon the qualities of the gums, the proportion of oil and turpentine and the care which is exercised in the boiling process.
158.Flowing Copal Varnish.—(1) Lay on the var nish quickly in a good heavy coat. Use a good varnish brush and dip the bristles deeply into the liquid, wiping them off just enough to prevent dripping. (2) Wipe the
bristles quite free of varnish; go over the surface and pick up as much of the surplus liquid as the brush will hold. Replace the varnish in the can by wiping the bristles on the wire of the can. Repeat until the entire surface has been left with but a thin smooth coating.
Two, three, four or more coats are applied in this manner, forty-eight hours being allowed between each for drying. Dry varnish comes off in sanding as a white powder; if not dry it will come off on the sandpaper as little black spots.
159. Typical Finishes for Coarse-grained Woods. —Egg-shell gloss: (1) One coat of water stain, English golden, etc., according to the result desired. (2) Allow time to dry, then sandpaper lightly with fine sandpaper. This is to smooth the grain and to bring up the highlights by removing stain from some of the wood. Use No. 00 sandpaper and hold it on the finger tips. (3) Apply a second coat of the stain diluted about one-half with water. This will throw the grain into still higher relief and thus produce a still greater contrast. Apply this coat of stain very sparingly, using a rag. Should this stain raise the grain, again rub lightly with fine worn sandpaper, just enough to smooth. (4) When this has dried, put on a light coat of thin shellac. Shellac precedes filling that it may prevent the high lights—the solid parts of wood—from being discolored by the stain in the filler, thus causing a muddy effect. The shellac being thin does not interfere with the filler's entering the pores of the open grain. (5) Sand lightly with fine sandpaper. (6) Fill with paste filler colored to match the stain. (7) Cover this with a coat of orange shellac. This coat of shellac might be omitted but another coat of varnish must be added. (8) Sandpaper lightly. (9) Apply two or three coats of varnish. (10) Rub the first coats with hair cloth or curled hair and the last with pulverized pumice stone and crude oil or raw linseed oil.
Dull finish: A dead surface is obtained by rubbing the varnish, after it has become bone dry, with powdered pumice stone and water, using a piece of rubbing felt. Rub until the surface is smooth and even, being careful not to cut thru by rubbing too long at any one spot. The edges are most likely to be endangered. Use a wet sponge and chamois skin to clean off the pumice.
Polished finish: The last coat should be rubbed first with pulverized pumice stone and water, and then with rotten stone and water. For a piano finish rub further with a mixture of oil and a little pulverized rotten stone, vising a soft felt or flannel. A rotary motion is generally used and the mixture is often rubbed with the bare hand.
Gloss finish. For a gloss finish, the last coat is not rubbed at all.
160. Patching.—It frequently happens in rubbing with pumice that the varnish is cut thru so that the bare wood shows. To patch such a spot proceed as follows: (1) Sandpaper the bare place lightly with very fine paper, No. 00, to smooth the grain of the wood raised by the pumice water. (2) If the wood has been stained or filled, color the spot to match the rest of the finish. Apply a little with a cloth and wipe off clean. (3) When this has dried, carefully apply a thin coat of varnish to the bare wood. Draw it out beyond the bare wood a little, "feathering" it so that there shall not be a ridge. (4) Allow this to dry hard and apply a second coat, feathering it beyond the surface covered by the first coat. (5) Repeat until the required thickness has been obtained; then (6) rub with pumice and water. Rub lightly, using a little pumice and much water. The slightly raised rings made by the lapping of one coat upon another will need special attention. It is best not to sandpaper between coats, because of the danger of scratching the rubbed finish adjoining the patch.
161. Painting.—The purpose of paints is to preserve the wood by covering it with an opaque material. Paints are usually composed of white lead or zinc oxide and coloring materials mixed or thinned with raw or boiled linseed oil. Turpentine is also used for thinning and as a drying agent. Paint must be well brushed out so that a thin film may result.
In painting, (1) Cover the knots with shellac, or the oil of the paint will be absorbed thru two or three coats and discoloration result. (2) Put on a prime coat. This coat should be mixed as thin as it can be and still not "run" when applied to vertical surfaces. (3) Fill the nail holes with putty. Sand lightly if a smooth finish is desired. (4) Apply two or three coats of paint thin enough to flow freely but thick enough to cover well and not "run."
The second coat is given a little more than the usual amount of turpentine that a "flat effect" may prepare the way for the final gloss coat. If the last coat is to be dull, turpentine is used in it as well as the second. Oil causes gloss, turpentine causes a dull or flat effect.