The function of stains is to change the color, and to enchance the grain and texture of the wood. Stains may be divided into four general classes, which are not, however, entirely distinct. (1) Oil stains, (2) Water stains, (a) made from anilines, (b) made from dyes other than anilines, (3) Spirit stains, (4) Stains due to chemical changes.
(1) Oil stains. Advantages: they are easily prepared, are easy to apply evenly, and they
The pigments most used for oil stains are: burnt and raw umber, burnt and raw sienna, Vandyke brown, drop black, and medium chrome yellow. These colors may be varied by mixing. For example, for a green stain, take two parts of drop black and one part of medium chrome yellow, and dissolve in turpentine or benzine. The addition of a little vermilion gives a grayer green. The green may be made bluer by the addition of Prussian blue, but the blue already contained in the black gives a soft, pleasant green.
For antique oak, add a trifle of burnt umber and black to raw sienna thinned to the right consistency.
For a reddish brown, thin burnt umber to the right consistency. This may be grayed by the addition of a little green.
A walnut stain may be had by adding a little Venetian red to asphaltum, thinned with turpentine or benzine.
Aniline oil stains. Advantages: the colors are clear and easily obtainable. Disadvantages: the colors are likely to be crude and too bright, and unless great care is taken the tones are metallic and not soft enough to suit wood. It is necessary to purchase colors soluble in oil. These can be had of William Zinnser and Company, 197 William Street, New York. Four colors are necessary to get the desired shades, Bismarck brown, dark yellow, dark blue, and black. Bismarck brown comes in powdered form at $2.40 per lb., dark yellow comes in powdered form at $2.40 per lb., dark blue comes in lumps at $3.20 per lb., black comes in lumps at $2.40 per lb. These may be dissolved in three ounces of turpentine to one ounce of boiled oil, to one teaspoonful of color, a process that will take place much faster if the mixture is heated. Great care must be taken, however, not to set fire to the turpentine. When cool, thin with turpentine to the proper consistency, apply to the wood with a brush and rub clean with cotton waste.
(2) Water Stains. Advantages: they are cheap and clear and do not obscure the grain as oil stains are likely to do, and they penetrate deeply into the wood, especially when applied hot. They may be made of any coloring matter that is soluble in water, and are particularly good for hard woods and for use in large quantities. It is possible to stain wood much darker with them than with oil stains. Moreover, the brushes used with them are easily taken care of. Disadvantages: they are difficult to prepare and they raise the grain of the wood. The former disadvantage may be overcome by buying them all prepared.
The difficulty of the raising of the grain is to be obviated either by washing the wood in water and, when dry, rubbing down with sandpaper before applying the stain, or rubbing down after staining and re-staining when necessary.
a. Water stains made from anilines. Aniline stains are likely to fade, but the addition of a little vinegar is said to hinder fading. For Mahogany, dissolve 1 oz. Bismarck brown in 3 quarts of boiling water. Use when cool.
b. Water stains made from dyes other than anilines. The number of these is legion; some of the simpler are given.
Reddish Brown. Dissolve extract of logwood of the size of a walnut in ½ cup (4 oz.) of hot water. Apply hot to wood repeatedly until desired color is obtained.
Black. Dissolve extract of logwood of the size of a walnut in ½ cup (4 oz.) of boiling water. Add a teaspoonful of alum. Apply repeatedly until the wood is dark brown. Prepare acetate of iron according to directions for making dark brown, on next page. Apply this to wood already browned with logwood. If the grain is raised, sandpaper lightly, or rub with steel wool and then with boiled oil.
(3) Spirit Stains. These are expensive and hence little used. A few illustrations are given.12
Footnote 12: For detailed directions for treatment of different woods, see Hodgson, pp. 112-153.
Black. Aniline black, cut in alcohol, gives a bluish effect but if the wood thus stained is rubbed with raw linseed oil, it becomes black.
Another Black. Dissolve extract of logwood in wood alcohol. Develop the color by going over the work with tincture of muriate of iron.
Golden Oak. Dissolve asphaltum in naphtha until it is as thin as water and makes a yellowish stain; or to equal parts of asphaltum, varnish, and gold size japan, add enough turpentine to thin to proper consistency.
Mahogany. Dissolve Bismarck Brown in alcohol.
Aniline stains may be cut in alcohol and mixed with equal parts of white shellac and banana oil (amyl acetate) and all applied in one coat.
(4) Stains due to chemical changes. Certain substances like ammonia, potassium bichromate, and acetate of iron, give chemical reactions on certain woods and make very effective and inexpensive stains. Moreover the artistic effect of some of them is unexcelled. When applied in solution they are likely to raise the grain.
The effect of ammonia, either the liquid or fumes, is much the same as the effect produced by aging or weathering. Ammonia also cuts the pith rays of oak and makes it possible for other stains to take hold. For this reason it is much used as a preliminary treatment for oak finishes. The color effect is to lessen the yellow and increase the gray.
The method of application is simply to expose the wood for a day or more to the fumes of strong ammonia (28%) in a tightly closed box. If the surface of the wood is moistened with water just before exposure, it turns darker than if exposed dry. The stain penetrates so deeply that it may be sandpapered after the exposure without harm. After fuming and sandpapering the surface should be oiled to prevent finger marks.
Dark brown for chestnut, or oak, or mahogany. This is obtained with a solution of acetate of iron, made as follows: digest one part by measure of iron dust in 8 parts of glacial acetic acid. After the chemical action is well started, add several times as much water to keep the mixture liquid. When the chemical action has ceased, the stain is ready for use. If a lighter shade is desired it may be still further diluted.
To darken mahogany. Make a saturate solution of bichromate of potash. Dilute a portion of it with water 1⁄2, or 1⁄3, or 1⁄4, or in any proportion according to the darkness required. One part of the solution to two or three parts of water gives a good color. Apply the solution to mahogany with a brush. This solution alone is likely to be too brown. The reddish tinge of the wood may be saved by mixing as follows:
|100% solution of bichromate of potash
|Breinig's mahogany water stain
|Apply with a brush and wipe off the surplus.
Bichromate of potash on oak gives a rich brown.
Bichromate of potash on ash gives a rich red.
Bichromate of potash on black walnut gives a dark brown.
A decoction of logwood treated with tannin gives yellow red, with sugar of lead gives gray brown, with ferric nitrate gives black. A decoction of fustic extract treated with dilute nitric acid gives brown, etc.13
Footnote 13: For other effects obtained by chemical changes, see table on pp. 185-189 in Brannt's Painter, Gilder and Varnisher, and also Woodcraft 9: 71, June, '08.
Commercial Stains. Some of the more noteworthy commercial stains, suitable for school use, are those of:
The Bridgeport Wood Finishing Company, 55 Fulton St., New York. Among their water stains some of the best are: Flemish oak, weathered oak, walnut, silver gray, forest green, and mahogany, especially if the latter is modified with bichromate of potash. Other effects may be obtained by mixing these, as forest green, which is too bright alone, mixed with walnut or some other reddish color gives a grayish green. Of the penetrating oil stains the golden oak and mahogany are very good.
The Sherwin Williams Company, of Cleveland, Newark, Chicago, etc., produce a fine line of spirit stains.
The Adams and Elting Company, Chicago, have a stain called adelite, in which banana oil appears to be the solvent. It is very easy of application, only one coat being needed. It is applied with the brush.
Berry Brothers, of Detroit, Mich., the famous varnish makers, furnish a great variety of colors in their water stains and also a combined stain and finish under the trade name of Lacklustre.
Devoe and Reynolds, 101 Fulton Street, New York, make a variety of oil stains which can be applied either in one coat with a brush or rubbed in with cotton waste.
The Chicago Varnish Company, make a specialty of artistic, chemical stains, but unfortunately they are not yet (1910) available in small quantities.
S. C. Johnson and Son, Racine, Wis., furnish a variety of spirit stains called "wood dyes."
The Craftsman Workshops, Eastwood, N. Y., furnish oil stains to be applied with a brush or waste. These are deservedly famous for they give especially soft, agreeable effects on fumed oak.
In general, it should be remembered that oil stains are better for soft woods, water stains for hard woods, and the spirit stains are good for both. But without a sense of color, no number of recipes will avail.
The object of filling is to give a perfectly level and non-absorbent basis for varnish covering or other finish. This can be done with shellac carefully rubbed down with fine oiled sandpaper, but this method requires much toil and patience, and has therefore been given up by furniture finishers. The best fillers, (such as "Wheeler's Wood filler"),14 are made of silex in needle-shaped particles mixed with raw linseed oil, japan and turpentine. When applied to wood it should be thinned with turpentine or benzine, and applied with a brush along the grain. As it dries, the color becomes grayish and it should then be rubbed off across the grain with fine shavings or cotton waste. It is best to have fillers of several colors on hand, such as light, black, mahogany, and "golden oak" to be used according to the stain applied. The filler should be applied after staining the wood and should be allowed to dry thoroly, say forty-eight hours, before it is covered with shellac or varnish. Its use is more necessary on open grained woods, like oak, chestnut, and mahogany, than on close grained woods, like whitewood, maple, and pine, but it is best to use it on all woods that are to be highly polished.
Footnote 14: Made by the Bridgeport Wood Finishing Co., 155 Fulton St., N. Y.
Cans should be kept tightly covered when not in use. Since oil darkens wood, if wood is to be kept light, a filler without oil, as whiting and turpentine, should be used.
There are three principal forms of wood polishes, each of which has its virtues and defects. They are: (a) oil, (b) wax, (c) the varnishes.
(a) Oil. The great advantage of oil polishing is its permanence. It will stand both wetting and warmth and gives a dull, glossy finish. In some woods, as sweet gum and mahogany, it brings up the figure.
Process. Apply either raw or boiled linseed oil diluted with five parts of benzine or turpentine. The advantages of dilution are that the mixture penetrates the wood better, leaves a thinner film on the surface and is more economical. Then rub, rub, rub, day after day. Little and often with unlimited friction, is the best rule. This makes a nice finish for well-fumed chestnut, turning the color to a rich brown.
(b) Wax. Wax is an old English polish, commonly used before French polish and varnish were introduced, especially for hard woods like oak. Its advantages are that it is cheap, easily prepared, easily applied, and easily repaired. Its disadvantages are that it will not stand wetting, is easily marred, requires constant care, is not so hard and dry as varnish, turns slightly sticky with warmth, and is likely to turn white in crevices.
To prepare it. To one part of melted beeswax add one part of turpentine. Mix and cool. It can be bought prepared, as, Bridgeport Wood Finishing Company's "Old Dutch Finish," Butcher's Wax, Johnson's Wax, and others.
Process. Rub the wax evenly over the surface with a stiff brush or the fingers. Let it dry for some hours, and then rub with a cloth: flannel or a piece of felt is best. Put on several coats, leaving the work over night between coats. Rub often with a warm cloth.
(c) Varnishes. The function of varnishes is to cover wood with a hard, transparent coating that is non-porous and impervious to moisture. There is a great range among them, from thin, easily worn, dull finishes to durable, strong, and highly polished coatings called "rubbing varnishes." The polished surface can be secured only by much labor thru the application of successive thin coats of good varnish, carefully rubbed down.
Varnish may be applied to wood, stained, painted, or in its natural condition as well as to metal, leather, paper, and various other substances. A good varnish should be adhesive, that is, it should cling firmly to the surface to which it is applied; it should be elastic, so as not to crack on account of the expansion and contraction of the material to which it is applied; it should dry in a reasonable time; it should be limpid so as to flow easily in application; it should be transparent and brilliant when polished; and it should be durable. The necessary conditions for all good varnishing are a perfectly smooth, even, filled surface of dry wood, a temperature of about 70° and no dust in the air.
In general, there are two classes of varnish, based on the character of the solvent, (1) Spirit varnishes and (2) Oil varnishes.
(1) Spirit varnishes are sometimes made with copal resins dissolved in some spirit, as one of the alcohols, benzine, acetone, etc. They dry with great rapidity owing to the volatilization of the solvent spirit, leaving a coat of pure resin of great hardness and brilliance, but one which is likely to crack and scale when exposed. They are not much used. Shellac is the most common and the most useful of the spirit varnishes. Its basis is resin lac, a compound resinous substance exuded from an East India scale insect (Carteria lacca) found mostly in the province of Assam. The term "lac" is the same as "lakh" which means 100,000 and is indicative of the countless hosts of insects which are the source from which this gum is obtained. The larval insects insert their proboscides into the bark of young shoots of certain lac-bearing trees, varieties of Ficus, draw out the sap for nutriment, and at once exude a resinous secretion which entirely covers their bodies and the twigs, often to the thickness of one-half inch. The females never escape and after impregnation their ovaries become filled with a red fluid which forms a valuable dye known as lac dye. The encrusted twigs are gathered by the natives in the spring and again in the autumn, before the young are hatched, and in this condition the product is known as "stick lac." After being crushed and separated from the twigs and washed free from the coloring matter the product is known as "seed lac." It is then melted and strained and spread out in thin layers in a form called "shell lac." This is what is known as orange shellac in the market. It may be bleached by boiling in caustic potash, and passing chlorine thru it until the resin is precipitated. It is further whitened by being pulled. This is what is known in the market as "white shellac." It comes in lumps. Orange shellac is the stronger and is less likely to deteriorate, but white is easier to apply because it sets less rapidly. Another advantage of the white is its colorlessness. Shellac is soluble in both grain alcohol (ethyl alcohol) and wood alcohol (methyl alcohol), but grain alcohol is preferable. Great care must be taken not to mix even a drop of water in it or it will curdle. To make perfect the process of ordinary filling, shellac may be used as a filler either by itself or preparatory to other processes. Since it dries quickly it can be rubbed down in six or eight hours either with No. 00 sandpaper oiled, or better, with No. 00 steel wool. This process when repeated several times gives a good "egg-shell" finish. It may be applied alone over stained wood or the shellac itself may be colored with aniline dyes cut in alcohol. This, for example, is an easy way to get a black finish.
A good waterproof wood polish is made thus: 1 pint alcohol, 2 oz. gum benzoin, ¼ oz. gum sandarac, ¼ oz. gum anime. Put in a bottle, and put the bottle in a hot water bath until all solids are dissolved. Strain and add ¼ gill clear poppy oil. Shake well and apply with cotton cloth.
A soft, dull, glossy finish may be obtained by applying two coats of a mixture of one part each of white shellac and banana oil (amyl acetate). When dry, sandpaper lightly and wax.
French polishing. The finest of shellac finishes is French polish. It is a thin, clear, permanent finish, but the process takes time and patience. It is not much used in practical work, because of the time expense, but is often employed in school shops, because only a few materials are necessary, it dries quickly, and gives a beautiful finish. The polished surface is obtained by adding successive thin coats according to the following process:
(1) Preparation. The surface of the wood must be perfectly smooth and even, sandpapered in the direction of the grain, stained, if desired, filled, rubbed smooth and quite dry. (2) Apply two or three thin coats of shellac. After each coat when dry, rub with No. 00 oiled sandpaper or No. 00 steel wool. Wipe thoroly. (3) Make three pads, about the size of a walnut, of clean, white, cotton waste, enclosed in some fine old or washed cloth with no sizing or lint,—one pad for shellac, one for oil, and one for alcohol. Fill one pad with shellac of the consistency of milk, enough in the pad so that when squeezed hard it will ooze out. The common mistake is to put too much shellac into the pad. Rub with circular motion, as indicated in Fig. 304, never letting the pad stop on the surface. (4) Sprinkle a very little finely powdered pumicestone and put a little oil on the surface of the wood here and there with the tip of a finger. Rub with second pad until surface is dull. Wipe clean. Repeat (3) and (4) several times. Some use raw linseed oil to prevent sticking. Others use three or four cloth coverings on the shellac pad, removing the outer one as it dries. A simpler way is to keep the shellac in pad, 1, thin by moistening with a little alcohol. (5) Spiriting off (Follows process 4.) Dampen pad, 3, with very little alcohol and wipe quickly in the direction of the grain. This should remove the circular marks. Too much alcohol in this third pad will "burn" a dull spot. The rubbers are said to improve with use, and may be preserved in closely stoppered jars to prevent evaporation. The different kinds of pads should be kept separate. Or the cotton waste may be thrown away, and the cloths washed in strong borax water. In the process just described, shellac alone, dissolved in alcohol, is used. The shellac may be used with other ingredients: for example, 1 pint grain alcohol, ¼ oz. gum copal, ¼ oz. gum arabic, 1 oz. shellac. Strain through muslin.
Another recipe for finishing. Use 4 drams grain alcohol, 2 drams orange shellac, 5 drams tincture of benzoin, 1 teaspoonful of olive oil. Dissolve and strain. Apply with pad in direction of grain.
Oil or Copal Varnishes. The old Cremona varnish once used for violins is supposed to have had amber (Greek, electron) as its base. It was a fossilized coniferous resin found on the shore of the Baltic Sea. The art of making it is said to be lost, probably because of the difficulty and danger of melting it, for this can be done only in oil on account of the danger of ignition. Hence its use has been abandoned.
Perhaps the most beautiful of all varnishes is lacquer, much used in China and Japan. It is made from the juice of the lacquer tree, (Rhus vernicifera) which is tapped during the summer months. The juice is strained and evaporated and then mixed with various substances, such as oil, fine clay, body pigment, and metallic dust, according to the ware for which it is intended. The manufacturing secrets are carefully guarded. The application of it is very difficult, the sap of young trees being used for first coats, and of old trees for the finishing coats. It must be dried in a damp, close atmosphere. For the best work ten or twelve coats are elaborately rubbed down and polished. Even the presence of it is very poisonous to some people and all workers in it are more or less affected.
The solvent or vehicle of the modern copal varnishes consists principally of linseed oil with some turpentine. Their base is Copal, a fossil, resinous substance of vegetable origin. The gums of which they are made have been chemically altered by long exposure in the earth. Other gums, as mastic, dammar, sandarac, and even resin are sometimes mixed with copal to cheapen the product or to cause more rapid drying. Copal is a generic name given originally to all fossil resins. Copals, as they are called, come from New Zealand, Mozambique, Zanzibar, West Africa, Brazil, and the Philippines. The best of the Copals is said to be the Kauri gum, originally exuded from the Kauri pine tree of New Zealand. The tree is still existent and produces a soft, spongy sap, but the resin used in varnish is dug up from a few feet under ground in regions where there are now no trees. A commercially important copal and one noted for its hardness is the Zanzibar or East African Copal. It is found imbedded in the earth at a depth not greater than four feet over a wide belt of the mainland coast of Zanzibar, on tracts where not a single tree now grows. It occurs in lumps from the size of small pebbles to pieces weighing four or five pounds. The supply is said to be practically inexhaustible.
As to the manufacture of the Copal varnishes: first of all, a high grade oil is boiled at a high temperature, with different materials to oxidize it; for instance, red lead or oxide of manganese. The heat throws off the oxygen from the red lead or manganese. The oxygen is absorbed by the linseed oil, which is then put away to settle and age. When a batch of varnish is made, the gums are melted in a large kettle and then the requisite amount of oil is added and these carefully boiled together. This is removed from the fire and cooled down to a point, where turpentine can be added without volatilizing. These are thoroly mixed and then filtered under pressure and tanked and aged. The different grades of varnish depend upon the treatment of the oil, the proportion of oil and turpentine, the qualities of the gums, the aging, etc. Some by rubbing give a very high polish, some give a dull waxy finish, some are for out-of-door use, as Spar varnish and carriage varnish, some are for floors, some for furniture, some are high priced, some are cheap.
Process of Varnishing. The preliminary processes are the same as those for applying shellac, i. e., the surface of the wood must be perfectly even and smooth, and the staining, filling, and drying complete. Quick drying varnishes, like shellac, are applied, with but little on the brush. The heavy, high lustre varnishes, on the other hand, are applied with the brush full so that the varnish may even drip off the work. Then proceed as follows: Wipe off from the work the extra varnish with the brush and clean the brush on the edge of the cup. Repeat till the varnish is flowed over the work evenly. Be particularly careful, in that respect, of edges and corners. Set to dry in a dustless place. When dry and hard repeat the process from three to six times. Each coat must dry thoroly before the next coat is applied.
Varnish polishing consists in rubbing off the varnish, not in rubbing it on, as in French polishing. To polish varnish, rub with a felt pad, powdered pumice-stone and water. Rub till the surface is smooth, unpitted and even, being careful not to rub thru the edges. Wipe clean with a wet sponge and chamois skin. This gives a dull or "egg-shell" finish. For polishing varnish, a simple method is to rub with a rotary motion, using a mixture of 1⁄2 sweet oil or cottonseed oil, and 1⁄2 alcohol.
A more laborious process is as follows: After rubbing to a dull finish, rub ground rotten stone and water with chamois skin in a circular motion. Let the rotten stone dry on the surface. Then wipe off with the naked hand, rubbing in a circular direction and wiping the hand every time after passing over the work. This looks simple, but is really a fine art. These processes have practically replaced French polishing in the trade.
Paints are used for the same purpose as other finishes, with the additional one of giving an opaque colored covering. The materials used are:
1. A body whose function is to give covering power. This is usually white lead, but it is often adulterated with zinc oxide; 2. Pigments; 3. Linseed oils, raw and boiled, which are used to give consistency, adhesiveness and also elasticity to the coat when dry. For outdoor work boiled oil is used and for indoor work, raw oil; 4. Turpentine, which is used to thin out the paint and to make it dry more quickly.
The common method of painting is: 1. Set any nails with nailset; 2. Sandpaper; 3. Shellac the knots; 4. Prime with a thin coat of paint, mostly white lead, (that is, little color,) boiled oil, and turpentine (the proportion of drying oil is greater than in ordinary paint); 5. Putty up cracks, nail holes, etc.; 6. Sandpaper if a small nice job; 7. Then paint two or three coats with paint thick enough so it will not run, with long, even strokes with the grain. The order of painting a door is, panels, muntins, rails, and last, stiles.
For inside work use half as much turpentine as oil. This gives a dull finish. For outside work, where lustre is wanted, little or no turpentine is used.
This is the old way, and is still used for all common work. But for fine painting, as carriage work, a filler is now used first, because a priming to be durable should unite with the wood, grasping the fibers and filling the pores, so that after coats cannot sink in. The object is to cement the surface. Priming is often called "rough stuff." The old way did not do this, with the result that the oil separated from the lead and kept soaking into the wood. The principal makers of paints now recommend a filler before any white lead is added.
Brushes. It is well to have several varieties to help keep them distinct. For varnish and shellac, the best are those with the bristles set in hard rubber. For ordinary purposes, brushes one inch wide are satisfactory. For stains, cheap, tin-bound brushes are good enough, and are easily replaced.
Cups. Half-pint enameled steel cups are cheap, satisfactory, and easily kept clean. For the care of cups and brushes, see Chapter VI, The Equipment and Care of the Shop.
Steel wool. This consists of shavings, turned from thin steel discs set together in a lathe. It comes in various grades, No. 00 to No. 3. The finest, No. 00, is coarse enough for ordinary purposes.
Sandpaper. Use No. 00 smeared with boiled oil. Pulverized pumice stone and pulverized rotten stone, both very fine, are used to rub down inequalities and to give a dull finish to shellac or varnish. Use with oil on shellac and with oil or water on copal varnish. Horsehair and soft wood shavings are often used to rub down varnish. French felt, medium hard, is used for rubbing down copal varnish with pumice stone.
Cotton waste is the cheapest available material for wiping.
Cheese cloth is better for some purposes, but more expensive.
Soft cloth without lint is necessary for French polishing. "Berkeley muslin," "Old Glory," and "Lilly White" are trade names. A fine quality is necessary. The starch should be washed out and the cloth dried before using, and then torn into little pieces, say 4" square.
Fillers consist of silex or of ground earths mixed with oil, japan, and turpentine. Their object is to give a perfectly level and non-absorbent basis for varnish covering.
Oils. Raw linseed oil is very fat and dries slowly. It is used for interior work.
Boiled oil is linseed oil boiled with litharge (PbO) and white vitriol, which removes much of the fatty ingredient and gives it drying quality.
Turpentine is a volatile oil from the sap of long-leaf pine. It is mixed with oil in painting to give further drying qualities.
Benzine is a cheap substitute for turpentine. It is a highly inflammable product of coal tar and evaporates quickly.
Drier is an oil in which resin has been dissolved. It is mixed with varnishes and paint to make them dry quickly. It is also sometimes used as a varnish itself.
Japan is a varnish-like liquid made of shellac or other resin, linseed oil, metallic oxides, and turpentine. It is used as a medium in which to grind colors and as a drier.