Part 144

XVIII.—A durable coating for wood is obtained by extracting petroleum asphalt, with light petroleum, benzine, or gasoline. For this purpose the asphalt, coarsely powdered, is digested for 1 to 2 days with benzine in well-closed vessels, at a moderately warm spot. Petroleum asphalt results when the distillation of petroleum continued until a glossy, firm, pulverizable mass of conchoidal fracture and resembling colophony in consistency remains. The benzine dissolves from this asphalt only a yellowish-brown dyestuff, which deeply enters the wood and protects it from the action of the weather, worms, dry rot, etc. The paint is not opaque, hence the wood retains its natural fiber. It is very pleasant to look at, because the wood treated with it keeps its natural appearance. The wood can be washed off with soap, and is especially suited for country and summer houses.

XIX.—A liquid to preserve wood from mold and dry rot which destroys the albuminous matter of the wood and the organisms which feed on it, so there are neither germs nor food for them if there were any, is sold under the name of carbolineum. The specific gravity of a carbolineum should exceed 1.105, and should give the wood a fine brown color. It should, too, be perfectly waterproof. The three following recipes can be absolutely relied on: _a._ Heat together and mix thoroughly 95 pounds of coal-tar oil and 5 pounds of asphalt from coal tar. _b._ Amalgamate together 30 pounds of heavy coal-tar oil, 60 pounds of crude wood-tar oil, and 25 pounds of heavy rosin oil. _c._ Mix thoroughly 3 pounds of asphalt, 25 pounds of heavy coal-tar oil, and 40 pounds of heavy rosin oil.

XX.—Often the wooden portions of machines are so damaged by dampness prevailing in the shops that the {780} following compound will be found useful for their protection: Melt 375 parts of colophony in an iron vessel, and add 10,000 parts of tar, and 500 parts of sulphur. Color with brown ocher or any other coloring matter diluted with linseed oil. Make a first light application of this mixture while warm, and after drying apply a second coat.

XXI.—For enameling vats, etc., 1,000 parts of brown shellac and 125 parts of colophony are melted in a spacious kettle. After the mass has cooled somewhat, but is still thinly liquid, 6.1 parts of alcohol (90 per cent) is gradually added. In order to prevent the ignition of the spirit vapor, the admixture of spirit is made at a distance from the stove. By this addition the shellac swells up into a semi-liquid mass, and a larger amount of enamel is obtained than by dissolving it cold. The enamel may be used for wood or iron.

The wood must be well dried; only then will the enamel penetrate into the pores. Two or three coats suffice to close up the pores of the wood thoroughly and to render the surface smooth and glossy. Each coating will harden perfectly in several hours. The covering endures a heat of 140° to 150° F. without injury. This glaze can also be mixed with earth colors. Drying quickly and being tasteless, its applications are manifold. Mixed with ocher, for instance, it gives an elegant and durable floor varnish, which may safely be washed off with weak soda solution. If it is not essential that the objects be provided with a smooth and glossy coating, only a preservation being aimed at the following coat is recommended by the same source: Thin, soluble glass (water glass) as it is found in commerce, with about 24 per cent of water, and paint the dry vessel rather hot with this solution. When this has been absorbed, repeat the application, allow to dry, and coat with a solution of about 1 part of sodium bicarbonate in 8 parts of water. In this coating silicic acid is separated by the carbonic acid of the bicarbonate; from the water glass (sodium silicate) absorbed by the pores of the wood, which, as it were, silicifies the wooden surfaces, rendering them resistive against the penetration of liquids. The advantages claimed for both processes are increased durability and facilitated cleaning.

XXII.—Tar paints, called also mineral or metallic paints, are sold in barrels or boxes, at varying prices. Some dealers color them—yellow ocher, red ocher, brown, gray, etc. They are prepared by mixing equal parts of coal tar and oil of turpentine or mineral essence (gasoline). The product, if it is not colored artificially, is of a brilliant black, even when cold. It dries in a few hours, especially when prepared with oil of turpentine. The paints with mineral essence are, however, generally preferred, on account of their lower cost. Either should be spread on with a hard brush, in coats as thin as possible. They penetrate soft woods, and even semi-hard woods sufficiently deep, and preserve them completely. They adhere perfectly to metals. Their employment can, therefore, be confidently advised, so far as concerns the preservation directly of iron cables, reservoirs, the interior surface of generators, etc. However, it has been shown that atmospheric influence or variations of temperature cause the formation of ammoniacal solutions, which corrode the metals. Several companies for the care and insurance of steam engines have for some time recommended the abandonment of tar products for applications of this kind and the substitution of hot linseed oil.

XXIII.—Coal-tar paints are prepared according to various formulas. One in current use has coal tar for a base, with the addition of gum rosin. It is very black. Two thin coats give a fine brilliancy. It is employed on metals, iron, sheet iron, etc., as well as on wood. It dries much quicker than the tars used separately. Its preserving influence against rust is very strong.

The following Tissandier formula has afforded excellent results. Its facility of preparation and its low cost are among its advantages. Mix 10 parts of coal tar, 1 to 1.6 parts of slaked lime, 4,000 parts of oil of turpentine, and 400 parts of strong vinegar, in which 1⁠/⁠5 part of cupric sulphate has been previously boiled. The addition of 2 or 3 cloves of garlic in the solution of cupric sulphate aids in producing a varnish, brilliant as well as permanent. The compound can be colored like ordinary paints.

XXIV.—Rectified rosinous oil for painting must not be confounded with oils used in the preparation of lubricants for metallic surfaces exposed to friction. It contains a certain quantity of rosin in solution, which, on drying, fills the pores of the wood completely, and prevents decomposition from the action of various saprophytic fungi. It is well adapted to the preservation of pieces to be buried in the ground or exposed to the inclemency {781} of the weather. Paints can also be prepared with it by the addition of coloring powders, yellow, brown, red, green, blue, etc., in the proportion of 1 kilo to 5 liters of oil. The addition ought to take place slowly, while shaking, in order to obtain quite a homogeneous mixture. Paints of this kind are economical, in consequence of the low price of rosin, but they cannot be used in the interior of dwellings by reason of the strong and disagreeable odor disengaged, even a long time after their application. As an offset, they can be used like tar and carbonyl, for stalls, stables, etc.

«To Prevent Warping.»—Immerse the wood to be worked upon in a concentrated solution of sea salt for a week or so. The wood thus prepared, after having been worked upon, will resist all changes of temperature.

«STAINS FOR WOOD.»

In the staining of wood it is not enough to know merely how to prepare and how to apply the various staining solutions; a rational exercise of the art of wood staining demands rather a certain acquaintance with the varieties of wood to be operated upon, a knowledge of their separate relations to the individual stains themselves; for with one and the same stain very different effects are obtained when applied to the varying species of wood.

Such a diversity of effects arises from the varying chemical composition of wood. No unimportant rôle is played by the presence in greater or lesser quantities of tannin, which acts chemically upon many of the stains and forms with them various colored varnishes in the fibers. Two examples will suffice to make this clear. (1) Let us take pine or fir, in which but little of the tanning principle is found, and stain it with a solution of 50 parts of potassium chromate in 1,000 parts of pure water; the result will be a plain pale yellow color, corresponding with the potassium chromate, which is not fast and as a consequence is of no value. If, with the same solution, on the contrary, we stain oak, in which the tanning principle is very abundant, we obtain a beautiful yellowish-brown color which is capable of withstanding the effects of both light and air for some time; for the tannin of the oak combines with the penetrating potassium chromate to form a brown dyestuff which deposits in the woody cells. A similar procedure occurs in the staining of mahogany and walnut with the chromate because these varieties of wood are very rich in tannin.

(2) Take some of the same pine or fir and stain it with a solution of 20 parts of sulphate of iron in 1,000 parts of water and there will be no perceptible color. Apply this stain, however, to the oak and we get a beautiful light gray, and if the stain be painted with a brush on the smoother oaken board, in a short time a strong bluish-gray tint will appear. This effect of the stain is the result of the combination of the green vitriol with the tannin; the more tannin present, the darker the stain becomes. The hardness or density of the wood, too, exerts a marked influence upon the resulting stain. In a soft wood, having large pores, the stain not only sinks further in, but much more of it is required than in a hard dense wood; hence in the first place a stronger, greasier stain will be obtained with the same solution than in the latter.

From this we learn that in soft woods it is more advisable to use a thinner stain to arrive at a certain tone; while the solution may be made thicker or stronger for hard woods.

The same formula or the same staining solution cannot be relied upon to give the same results at all times even when applied to the same kinds of wood. A greater or lesser amount of rosin or sap in the wood at the time the tree is felled, will offer more or less resistance to the permeating tendencies of the stain, so that the color may be at one time much lighter, at another darker. Much after the same manner we find that the amount of the tanning principle is not always equal in the same species of wood.

Here much depends upon the age of the tree as well as upon the climatic conditions surrounding the place where it grew. Moreover, the fundamental color of the wood itself may vary greatly in examples of the same species and thus, particularly in light, delicate shades, cause an important delay in the realization of the final color tone. Because of this diversification, not only in the different species of wood, but even in separate specimens of the same species, it is almost impossible always, and at the first attempt, to match a certain predetermined color.

It is desirable that trials at staining should first be made upon pieces of board from the same wood as the object to be stained; the results of such experiments furnishing exact data concerning the strength and composition of the stain to be employed for the exact reproduction of a prescribed color. {782} Many cases occur in which the color tone obtained by staining cannot always be judged directly after applying the stain. Especially is this the case when stain is employed which slowly develops under the action of the air or when the dyestuff penetrates only slowly into the pores of the wood. In such cases the effect of the staining may only be fully and completely appreciated after the lapse of 24 or 48 hours.

Wood that has been stained should always be allowed 24 or 48 hours to dry in ordinary temperatures, before a coat of varnish, polish, or wax is applied. If any dampness be left in the wood this will make itself apparent upon the varnish or polish. It will become dull, lose its glossy appearance, and exhibit white spots which can only be removed with difficulty. If a certain effect demand the application of two or more stains one upon the other, this may only be done by affording each distinct coat time to dry, which requires at least 24 hours.

Not all the dyes, which are applicable to wood staining, can be profitably used together, either when separately applied or mixed. This injunction is to be carefully noted in the application of coal tar or aniline colors.

Among the aniline dyes suitable for staining woods are two groups—the so-called acid dyes and the basic dyes. If a solution of an acid dye be mixed with a basic dye the effect of their antagonistic dispositions is shown in the clouding up of the stain, a fine precipitate is visible and often a rosin-like separation is noticeable.

It is needless to say that such a staining solution is useless for any practical purpose. It cannot penetrate the wood fibers and would present but an unseemly and for the most part a flaky appearance. In preparing the stains it is therefore of the greatest importance that they remain lastingly clear. It would be considerably of advantage, before mixing aniline solutions of which the acid or basic characteristics are unknown, to make a test on a small scale in a champagne glass and after standing a short time carefully examine the solution. If it has become cloudy or wanting in transparency it is a sign that a separation of the coloring matter has taken place.

The mixing of acid or basic dyestuffs even in dry powdered form is attended with the same disadvantages as in the state of solubility, for just as soon as they are dissolved in water the reactions commence and the natural process of precipitation takes place with all its attending disagreeable consequences.

«COLOR STAINS:»

«Bronze.»—I.—Prepare first a thin glue size by soaking good animal glue over night in cold water and melting it next morning in the usual water bath. Strain it, before using, through old linen or cheese cloth into a clean vessel. Sandpaper smooth and dust the articles, then apply with a soft bristle brush 2 or 3 coats of the size, allowing sufficient time for each coat to harden before applying the next. Now, a ground coat made by thoroughly mixing finely bolted gilders’ whiting and glue size is applied, and when this has become hard it is rubbed to a smooth, even surface with selected fine pumice, and then given 1 coat of thin copal varnish. When this is nearly but not quite dry, the bronze powder is applied with a suitable brush or wad of cotton, and when dry the surplus bronze is removed with the same tool. If collected on clean paper, the dusted-off bronze powder may be used again.

II.—Diluted water-glass solution makes a good ground for bronze. Bronze powder is sprinkled on from a wide-necked glass tied up with gauze, and the excess removed by gently knocking. The bronze powder adheres so firmly after drying that a polish may be put on by means of an agate. The process is especially useful for repairing worn-off picture frames, book ornamentations, etc. The following bronze ground also yields good results: Boil 11,000 parts of linseed oil with 25 parts of impure zinc carbonate, 100 parts of red lead, 25 parts of litharge, and 0.3 parts of mercuric chloride, until a drop taken out will stand like a pea upon a glass surface. Before complete cooling, the mass is diluted with oil of turpentine to a thick syrup.

«Ebony Stains.»—I.—To 1 pint of boiling water add 3⁠/⁠4 ounce of copperas and 1 ounce logwood chips. Apply this to the wood hot. When the surface has dried thoroughly wet it with a solution composed of 7 ounces steel filings dissolved in 1⁠/⁠4 pint of vinegar.

II.—Give the wood several applications of a stout decoction of logwood chips, finishing off with a free smear of vinegar in which rusty nails have been for some time submerged.

III.—In 1 quart of water boil 1⁠/⁠4 pound of logwood chips, subsequently adding 1⁠/⁠2 ounce pearl ash, applying the mixture {783} hot. Then again boil the same quantity of logwood in the same quantity of water, adding 1⁠/⁠4 ounce of verdigris and 1⁠/⁠4 ounce of copperas, after which strain and put in 1⁠/⁠4 pound of rusty steel filings. With this latter mixture coat the work, and, should the wood not be sufficiently black, repeat the application.

«Metallic Luster.»—A valuable process to impart the luster of metal to ordinary wood, without injuring its natural qualities, is as follows: The wood is laid, according to its weight, for 3 or 4 days in a caustic alkaline solution, such as, for instance, of calcined soda, at a temperature of 170° F. Then it is at once placed in a bath of calcium hydrosulphite, to which, after 24 to 36 hours, a saturated solution of sulphur in caustic potash is added. In this mixture the wood is left for 48 hours at 100° to 120° F. The wood thus prepared, after having been dried at a moderate temperature, is polished by means of a smoothing iron, and the surface assumes a very handsome metallic luster. The effect of this metallic gloss is still more pleasing if the wood is rubbed with a piece of lead, zinc, or tin. If it is subsequently polished with a burnisher of glass or porcelain, the wood gains the brilliancy of a metallic mirror.

«Nutwood.»—One part permanganate of potassium is dissolved in 30 parts clear water; with this the wood to be stained is coated twice. After an action of 5 minutes, rinse off with water, dry, oil, and polish. It is best to prepare a fresh solution each time.

«Oak.»—I.—Water-color stains do not penetrate deep enough into wood to make the effect strong enough, hence solutions of other material than color are being employed for the purpose. Aqua ammonia alone, applied with a rag or brush repeatedly, will darken the color of oak to a weathered effect, but it is not very desirable, because of its tendency to raise the grain. Bichromate of potash, dissolved in cold water, applied in a like manner, until the desired depth is obtained, will serve the purpose. These washes or solutions, however, do not give the dark, almost black, effect that is at the present time expected for weathered oak, and in order to produce this, 4 ounces of logwood chips and 3 ounces of green copperas should be boiled together in 2 quarts of water for 40 minutes and the solution applied hot. When this has dried it should be gone over with a wash made from 4 ounces steel filings and 1 pint of strong vinegar. The steel filings are previously put into the vinegar and allowed to stand for several days. This will penetrate into the wood deeply, and the stain will be permanent. Picture-frame manufacturers use a quick-drying stain, made from aniline blacks.

II.—Dissolve 1⁠/⁠4 part of permanganate of potassium in 1,000 parts of cold water and paint the wood with the violet solution obtained. As soon as the solution comes in contact with the wood it decomposes in consequence of chemical action, and a handsome light-brown precipitate is produced in the wood. The brushes used must be washed out immediately, as the permanganate of potassium destroys animal bristles, but it is preferable to use sponges or brushes of glass threads for staining. Boil 2 parts of cutch in 6 parts of water for 1 hour, stir while boiling, so that the rosiniferous catechu cannot burn on the bottom of the vessel; strain the liquid as soon as the cutch is dissolved, through linen, and bring again to a boil. Now dissolve therein 1⁠/⁠5 part of alum, free from iron; apply the stain while hot, and cover after the drying, with a solution of 1 part of bichromate of potassium in 25 parts of water.

«Rosewood.»—First procure 1⁠/⁠2 pound logwood, boiling it in 3 pints water. Continue the boiling until the liquid assumes a very dark color, at which point add 1 ounce salt of tartar. When at the boiling point stain your wood with 2 or 3 coats, but not in quick succession, as the latest coat must be nearly dry before the succeeding one is applied. The use of a fiat graining brush, deftly handled, will produce a very excellent imitation of dark rosewood.

«Silver Gray.»—This stain is prepared by dissolving 1 part of pyrogallic acid in 25 parts of warm water and the wood is coated with this. Allow this coating to dry and prepare, meanwhile, a solution of 2 parts of green vitriol in 50 parts of boiling water, with which the first coating is covered again to obtain the silver-gray shade.

«Walnut.»—I.—Prepare a solution of 6 ounces of a solution of permanganate of potassium, and 6 ounces of sulphate of magnesia in 2 quarts of hot water. The solution is applied on the wood with a brush and the application should be repeated once. In contact with the wood the permanganate decomposes, and a handsome, lasting walnut color results. If small pieces of wood are to be thus stained, a very dilute bath is prepared {784} according to the above description, then the wooden pieces are immersed and left therein from 1 to 5 minutes, according to whether a lighter or darker coloring is desired.

II.—One hundredweight Vandyke brown, ground fine in water, and 28 pounds of soda, dissolved in hot water, are mixed while the solutions are hot in a revolving mixer. The mixture is then dried in sheet-iron trays.

«Yellow.»—The wood is coated with a hot concentrated solution of picric acid, dried, and polished. (Picric acid is poisonous.)

«IMITATION STAINS.»

Yellow, green, blue, or gray staining on wood can be easily imitated with a little glazing color in oil or vinegar, which will prove better and more permanent than the staining. If the pores of the wood are opened by a lye or a salt, almost any diluted color can be worked into it. With most stains the surface is thus prepared previously.

«Light-Fast Stains.»—Stains fast to light are obtained by saturating wood in a vacuum chamber, first with dilute sulphuric acid, then with dilute alkali to neutralize the acid, and finally with a solution with or without the addition of a mordant. The action of the acid is to increase the affinity of the wood for dye very materially. As wood consists largely of cellulose, mercerization, which always increases the affinity of that substance for dyes, may be caused to some extent by the acid.

«SPIRIT STAINS:»

«Black.»—

I.—White shellac 12 ounces Vegetable black 6 ounces Methylated spirit 3 pints

II.—Lampblack 1 pound Ground iron scale 5 pounds Vinegar 1 gallon

«Mahogany Brown.»—Put into a vessel, say 4 pounds of bichromate of potash, and as many ounces of burnt umber, let it stand a day or two, then strain or lawn for use.

«Vandyke Brown.»—

Spirit of wine 2 pints Burnt umber 3 ounces Vandyke brown color 1 ounce Carbonate of soda 1 ounce Potash 1⁠/⁠2 ounce

«Mahogany.»—Rub the wood with a solution of nitrous acid, and then apply with a brush the following:

I.—Dragon’s blood 1 ounce Sodium carbonate 6 drachms Alcohol 20 ounces

Filter just before use.

II.—Rub the wood with a solution of potassium carbonate, 1 drachm to a pint of water, and then apply a dye made by boiling together:

Madder 2 ounces Logwood chips 1⁠/⁠2 ounce Water 1 quart

«Maple.»—

I.—Pale button lac 3 pounds Bismarck brown 1⁠/⁠8 ounce Vandyke brown 1⁠/⁠2 ounce Gamboge 4 ounces Methylated spirit 1 gallon

II.—Use 1 gallon of methylated spirit, 4 ounces gamboge (powdered), 1⁠/⁠2 ounce Vandyke brown, 1 drachm Bismarck brown, 3 pounds shellac.