Chapter I: II III (9)

Before the plating the glass article is dipped into a cyanide dip, or, if found necessary, scoured lightly with pumice {575} stone and cyanide, and then given a dip in the customary blue dip or mercury solution, so as to quickly cover all parts of the surface. It next passes to the regular cyanide silver solution, and is allowed to remain until the desired deposit is obtained.

A little potassium cyanide and some mono-basic potassium citrate in powder form is added from time to time to the bath generally used, which is prepared by dissolving freshly precipitated silver cyanide in a potassium cyanide solution. After this the glass is rinsed and dried, and may be finished by buffing.

«Steel Plating.»—The following is a solution for dipping steel articles before electroplating: Nitrate of silver, 1 part; nitrate of mercury, 1 part; nitric acid (specific gravity, 1.384), 4 parts; water, 120 parts. The article, free from grease, is dipped in the pickle for a second or two.

The following electroplating bath is used: Pure crystallized ferrous sulphate, 40 parts, by weight, and ammonium chloride, 100 parts, by weight, in 1,000 parts, by weight, of water. It is of advantage to add to this 100 parts, by weight, of ammonium citrate, in order to prevent the precipitation of basic iron salts, especially at the anode.

«Tin Plating by Electric Bath.»—Most solutions give a dead-white film of tin, and this has to be brightened by friction of some sort, either by scratch brushing, burnishing, polishing, or rubbing with whiting. The bright tin plates are made bright by rolling with polished steel rollers. Small articles may be bright-tinned by immersion in melted tin, after their surfaces have been made chemically clean and bright, all of which processes entail much time and labor. Benzoic acid, boric acid, or gelatin may be tried with a well-regulated current and the solution in good working order, but all will depend upon the exact working of the solution, the same conditions being set up as are present in the deposition of other metals. These substances may be separately tried, in the proportion of 1 ounce to each gallon of the tin solution, by boiling the latter and adding either one during the boiling, as they dissolve much easier with the tin salts than in water separately. Tin articles are usually brightened and polished with Vienna lime or whiting, the first being used with linen rags and the latter with chamois leather. Tin baths must be used hot, not below 75° F., with a suitable current according to their composition. Too strong a current produces a bad color, and the deposit does not adhere well. A current of from 2 to 6 volts will be sufficient. Small tinned articles are brightened by being shaken in a leather bag containing a quantity of bran or by revolving in a barrel with the same substance; but large objects have to be brightened by other means, such as scratch brushing and mopping to give an acceptable finish to the deposited metal.

«GILDING AND GOLD PLATING:»

Genuine gilding readily takes up mercury, while imitation gilding does not or only very slowly. Any coating of varnish present should, however, be removed before conducting the test. Mercurous nitrate has no action on genuine gold, but on spurious gilding a white spot will form which quickly turns dark. A solution of neutral copper chloride does not act upon genuine gold, but on alloys containing copper a black spot will result. Gold fringe, etc., retains its luster in spirit of wine, if the gilding is genuine; if not, the gilding will burn and oxidize. Imitation gilding might be termed “snuff gilding,” as in Germany it consists of dissolved brass, snuff, saltpeter, hydrochloric acid, etc., and is used for tin toys. An expert will immediately see the difference, as genuine gilding has a different, more compact pore formation and a better color. There are also some gold varnishes which are just as good.

The effect of motion while an article is receiving the deposit is most clearly seen during the operation of gilding. If a watch dial, for instance, be placed in the gilding bath and allowed to remain for a few moments undisturbed and the solution of gold has been much worked, it is probable that the dial will acquire a dark fox-red color; but if it be quickly moved about, it instantly changes color and will sometimes even assume a pale straw color. In fact, the color of a deposit may be regulated greatly by motion of the article in the bath—a fact which the operator should study with much attention, when gilding.

The inside of a vessel is gilded by filling the vessel with the gilding solution, suspending a gold anode in the liquid, and passing the current. The lips of cream jugs and the upper parts of vessels of irregular outline are gilded by passing the current from a gold anode through a rag wetted with the gilding solution and laid upon the part.

Sometimes, when gilding the insides of mugs, tankards, etc., which are richly {576} chased or embossed, it will be found that the hollow parts do not receive the deposit at all, or very partially. When this is the case, the article must be rinsed and well scratch brushed, and a little more cyanide added to the solution. The anode must be slightly kept in motion and the battery power increased until the hollow surfaces are coated. Frequent scratch brushing aids the deposit to a great extent by imparting a slight film of brass to the surface.

In gilding chains, brooches, pins, rings, and other articles which have been repaired, i. e., hard soldered, sometimes, it is found that the gold will not deposit freely upon the soldered parts; when such is the case, a little extra scratch brushing applied to the part will assist the operation greatly and it has sometimes been found that dry scratch brushing for an instant—that is, without the stream of beer usually employed—renders the surface a better and more uniform conductor and consequently it will more readily receive the deposit. In fact, dry scratch brushing is very useful in many cases in which it is desirable to impart an artificial coating of brass upon an article to which silver or gold will not readily adhere. In scratch brushing without the employment of beer or some other liquid, however, great care must be taken not to continue the operation too long, as the minute particles of metal given off by the scratch brush would be likely to prove prejudicial to the health of the operator, were he to inhale them to any great extent.

The following solutions are for gilding without a battery: I.—In 1,000 parts of distilled water dissolve in the following order:

Crystalline sodium pyrophosphate 80 parts Twelve per cent solution of hydrocyanic acid 8 parts Crystalline gold chloride 2 parts

Heat to a boiling temperature, and dip the article, previously thoroughly cleaned, therein.

II.—Dissolve in boiling distilled water, 1 part of chloride of gold and 4 parts of cyanide of potassium. Plunge the objects into this solution, while still hot, and leave them therein for several hours, keeping them attached to a copper wire or a very clean strip of zinc. They will become covered with a handsome gold coating.

«Aluminum Gilding.»—I.—Dissolve 6 parts of gold in aqua regia and dilute the solution with distilled water; on the other hand, put 30 parts of lime in 150 parts of distilled water; at the end of 2 hours add the gold solution to the lime, shake all and allow to settle for 5 to 6 hours, decant and wash the precipitate, which is lime aurate. Place this aurate of lime in 1,000 parts of distilled water, with 20 parts of hyposulphite of soda; put all on the fire for 8 to 10 minutes, without allowing to boil; remove and filter. The filtered liquor serves for gilding in the cold, by plunging into this bath the aluminum articles previously pickled by passing through caustic potash and nitric acid. This gilding is obtained without the aid of the battery.

II.—The gold bath is prepared with gold dissolved in the usual way, and the addition of salts, as follows: Gold, 20 parts, by weight; sulphate of soda, 20 parts; phosphate of soda, 660 parts; cyanuret of potassium, 40 parts; water, 1,000 parts. The bath ought to be of the temperature of 68° to 77° F.

«Amalgam Gold Plating.»—Gold amalgam is chiefly used as a plating for silver, copper, or brass. The article to be plated is washed over with diluted nitric acid or potash lye and prepared chalk, to remove any tarnish or rust that might prevent the amalgam from adhering. After having been polished perfectly bright, the amalgam is applied as evenly as possible, usually with a fine scratch brush. It is then set upon a grate over a charcoal fire, or placed into an oven and heated to that degree at which mercury exhales. The gold, when the mercury has evaporated, presents a dull yellow color. Cover it with a coating of pulverized niter and alum in equal parts, mixed to a paste with water, and heat again till it is melted, then plunge into water. Burnish up with a steel or bloodstone burnisher.

«Brass Gilding.»—On brass, which is an electropositive metal, an electromagnetic metal, such as gold, can be deposited very cheaply from the dilute solutions of its salts. The deposit is naturally very thin, but still quite adhesive. In preparing it, the proportions stated below have to be accurately observed, otherwise no uniform, coherent coating will result, but one that is uneven and spotted.

I.—In 750 parts, by weight, of water dissolve: Phosphate of soda, 5 parts, and caustic potash, 3 parts, and in 250 parts of water, gold chloride, 1 part, and potassium cyanide, 16 parts. Mix both {577} solutions well and cause the mixture to boil, whereupon the brass articles to be gilded are immersed. The gold in the mixture can be utilized almost entirely. When the solution does not gild well any more a little potassium cyanide is added, and it is used for pre-gilding the articles, which can then be gilded again in a fresh solution. This solution is very weak. A stronger one can be prepared mechanically by dissolving 2 to 3 parts of gold chloride in very little water to which 1 part of saltpeter is added. Into this solution dip linen rags, let them dry in a dark place, and cause them to char into tinder, which is rubbed up in a porcelain dish. Into the powder so made, dip a soft, slightly charred cork, moistened with a little vinegar, or else use only the finger, and rub the gold powder upon the brass articles.

II.—To Give Brass a Golden Color, it is dipped until the desired shade is obtained into a solution of about 175° F., produced as follows: Boil 4 parts of caustic soda, 4 parts of milk sugar, and 100 parts of water for 15 minutes; next add 4 parts of blue vitriol, dissolved in as little water as possible.

«Copper and Brass Gilding.»—The solutions used to gild copper can be generally used also for brass articles. Copper gilding acquires importance because in order to gild iron, steel, tin, and zinc, they must first be coated with copper, if the boiling method is to be employed. Following is Langbein’s bath for copper and brass:

Dissolve 1 part, by weight, of chloride of gold and 16 parts, by weight, of potassium cyanide in 250 parts, by weight, of water; dissolve also and separately, 5 parts, by weight, of sodium phosphate and 3 parts, by weight, of caustic potash in 750 parts, by weight, of cold water. Mix these solutions and bring them to a boil. If the action subsides, add from 3 to 5 parts, by weight, more potassium cyanide. The polished iron and steel objects must first be copper-plated by dipping them into a solution of 5 parts, by weight, of blue vitriol and 2 parts, by weight, of sulphuric acid in 1,000 parts, by weight, of water. They may now be dipped into a hot solution containing 6 parts, by weight, of gold chloride and 22 1/2 parts, by weight, of soda crystals in 75 parts, by weight, of water. This coating of gold may be polished.

«Cold Chemical Gilding.»—The chemical gilding by the wet process is accomplished by E. E. Stahl with the aid of three baths: A gold bath, a neutralization bath, and a reduction bath. The gold bath is prepared from pure hydrochloric acid, 200 parts; nitric acid, 100 parts; and pure gold. The gold solution evaporated to crystallization is made to contain 1 1/2 per cent of gold by diluting with water. The neutralization bath consists of soda lye of 6°, of pure sodium hydroxide, and distilled water. The reduction bath contains a mixture of equal parts of 90 per cent alcohol and distilled water, wherein pure hydrogen has been dissolved. The gilding proper is conducted by first entering the article in the gold bath, next briskly moving it about in the neutralization bath, and finally adding the reducing bath with further strong agitation of the liquid. The residues from the gilding are melted with 3 parts each of potash, powdered borax, and potash niter, thus recovering the superfluous gold. The gilding or silvering respectively produces a deposit of gold or silver of very slight thickness and of the luster of polishing gold. Besides the metal solution an “anti-reducer” is needed, consisting of 50 grams of rectified and rosinified turpentine oil and 10 grams of powdered roll sulphur. From this is obtained, by boiling, a syrupy balsam, to which is added, before use, lavender oil, well-ground basic bismuth nitrate, and the solution for gilding or silvering. The last takes place by a hydrochloric solution of aluminum with the above balsam.

«Colored Gilding.»—A variety of shades of green and red gold can be obtained by the electro-chemical process, which method may be employed for the decoration of various objects of art. In order to produce red gold in the different shades, a plate of pure copper is hung into a rather concentrated gold bath (5 to 6 parts, by weight, per 1,000 parts of liquid), which is connected with the battery in such a manner that gold is deposited on the article immersed in the bath. By the action of the electric current copper is dissolved as well from the copper plate and is separated simultaneously with the gold, so that, after a certain time, a deposit containing a gold copper alloy, conforming in color to the quantities of gold and copper contained in it, is obtained by the electric process. When the desired shade of color of the deposit is reached the copper plate is taken out and replaced by another consisting of the copper gold alloy, likewise produced by electrodeposition, and the articles are now gilt in this liquid. In some large manufactories of gold articles this last coloring is used even for pure {578} gold articles, to give them a popular color. To produce green gold (alloy of gold and silver), a silver plate is first employed, which is dipped into the gold bath and from which enough silver is dissolved until the separating alloy shows the desired shade. The silver plate is then exchanged for a gold-silver plate of the respective color, and the articles are gilt with green gold.

«Gilding German Silver.»—In gilding German silver the solution may be worked at a low temperature, the solution being weakened and a small surface of anode exposed. German silver has the power of reducing gold from its solution in cyanide (especially if the solution be strong) without the aid of the battery; therefore, the solution should be weaker, in fact, so weak that the German silver will not deposit the gold _per se_; otherwise the deposit will take place so rapidly that the gold will peel off when being burnished or even scratch brushed.

«Gilding of Glass.»—I.—In order to produce a good gilding on glass, the gold salt employed must be free from acid. Prepare three solutions, viz.:

_a._ 20 parts acid-free gold chloride in 150 parts of distilled water.

_b._ 5 parts dry sodium hydrate in 80 parts of distilled water.

_c._ 2 1/2 parts of starch sugar in 30 parts distilled water; spirit of wine, 20 parts; and commercial pure 40 per cent aldehyde, 20 parts. These liquids are quickly mixed together in the proportion of 200, 50, and 5 parts, whereupon the mixture is poured on the glass previously cleaned with soda solution, and the gilding will be effected in a short time. The gold coating is said to keep intact for years.

II.—Coat the places to be gilded thinly with a saturated borax solution, lay the gold leaf on this and press down well and uniformly with cotton-wool. Heat the glass over a spirit flame, until the borax melts, and allow to cool off. If the glass is to be decorated with gilt letters or designs, paint the places to be gilded with water-glass solution of 40° Bé.; lay on the gold leaf, and press down uniformly. Then heat the object to 86° F., so that it dries a little, sketch the letters or figures on with a lead pencil, erase the superfluous gold, and allow the articles to dry completely at a higher temperature.

«Green Gilding.»—This can be obtained conveniently by the galvanic process, by means of anodes of sheet platinum with the following composition: Water, 10,000 parts, by weight; sodium phosphate, 200 parts; sodium sulphate, 35 parts; potassium carbonate, 10 parts; 1 ducat gold from gold chloride, potassium cyanide (100 per cent), 20 parts. Dissolve the first three salts in 10,000 parts of cold water and add, with stirring, the gold chloride and potassium cyanide. Before the first use boil down the solution thoroughly about one-half, replacing the evaporating water and filter after cooling, in case a sediment should appear. To this gold bath very carefully add some silver bath. The platinum sheets which are to serve as anodes are employed 1 3/4 inches long, 1/3 inch broad, and 1/100 of an inch thick. With these anodes the gold tone can be somewhat regulated by hanging more or less deeply into the solution during the gilding. The current should have a tension of 3 to 4 volts. In the case of batteries three Busen elements are connected for current tension. It is difficult to produce old gold on silver, especially if the raised portions are to appear green. It is most advantageous first to lightly copper the silver goods, taking the copper off again on the high places by brushing with pumice stone. After that hang at once in the above gold bath. If the embossed portions should be too mat, brighten slightly by scratching with a very fine brass wire brush. In this manner a handsome brown shade is obtained in the deep places and a green color on the raised portions. This process requires practice. Since this method will produce only a very light gilding, a coating of white varnish will protect the articles from tarnishing.

«Incrusting with Gold.»—The article is first made perfectly bright, and those places which are to be gilt are covered with a matt consisting of white lead ground with gum water, made into a paste which can be applied like a thick paint by means of a pen or brush. Those places of the metal surface not covered by the paint are coated with asphalt varnish—a solution of asphaltum in benzine to which oil of turpentine is added to render it less volatile. After this is done lay the article in water, so that the white lead paint comes off, and put it into a gilding bath. By the electric current gold is precipitated on the bright parts of the metal. When the layer of gold is thick enough lift the object from the bath, wash, let dry and lay it into a vessel filled with benzol. The asphalt dissolves in the benzol, and the {579} desired design appears in gold on the bronze or silver ground. This operation may also be performed by coating the whole article with asphalt varnish and executing the design by means of a blunt graver which only takes away the varnish covering without scratching the metal itself. On the parts thus bared gold is deposited by the electric current and the varnish coating is then removed.

«Ivory Gilding.»—I.—The pattern is painted with a fine camel’s-hair pencil, moistened with gold chloride. Hold the ivory over the mouth of a bottle in which hydrogen gas is generated (by the action of dilute sulphuric acid on zinc waste). The hydrogen reduces the auric chloride in the painted places into metallic gold, and the gold film precipitated in this manner will quickly obtain a considerable luster. The gold film is very thin, but durable.

II.—This is especially suitable for monograms. Take gold bronze and place as much as can be taken up with the point of a knife in a color-cup, moistening with a few drops of genuine English gold paint. Coat the raised portions sparingly with gold, using a fine pencil; next, coat the outer and inner borders of the design. When the work is done, and if the staining and gilding have been unsuccessful, which occurs frequently at the outset, lay the work for 5 or 10 minutes in warmed lead water and brush off with pumice stone. By this process very fine shades are often obtained which cannot be produced by mere staining. Since the gold readily wears off on the high places of the work, it is well to lightly coat these portions with a thin shellac solution before gilding. This will cause the gilding to be more permanent.

«Mat Gilding.»—To obtain a handsome mat gilding the article, after having been neatly polished, is passed through a sand-blast, such as is found in glass-grinding and etching establishments; next, the object is carefully cleansed of fine sand (if possible, by annealing and decocting), whereupon it is gilt and subsequently brushed mat with the brass brush. Where there is no sand-blast, the article is deadened with the steel wire brush, which will produce a satisfactory result, after some practice. After that, treatment is as above. The above-mentioned applies in general only to silver articles. In case of articles of gold, brass, or tombac, it is better to previously silver them strongly, since they are too hard for direct treatment with the steel wire brush, and a really correct mat cannot be attained. The brushes referred to are, of course, circular brushes for the lathe.

«Dead-Gilding of an Alloy of Copper and Zinc.»—The parts which are to be deadened must be isolated from those which are to be polished, and also from those which are to be concealed, and which therefore are not to be gilded. For this purpose they are coated with a paste made of Spanish white mixed with water. The articles prepared in this manner are then attached by means of iron wire to an iron rod and suspended in a furnace constructed for this process. The floor of this furnace is covered on four sides with plates of enameled earthenware for receiving the portions spattered about of the salt mixture given off later.

In the middle is an oven constructed like a cooking stove, on which is an iron tripod for carrying the deadening pan; this latter is cemented into a second pan of cast iron, the intervening space being filled up with stove cement. In the middle of the pan is the bottom or sill, provided with a thick cast-iron plate, forming the hearth. On all four sides of the latter are low brick walls, connecting with the floor of the furnace, and the whole is covered with thick sheet metal. On the side of the furnace opposite the side arranged for carrying the pans, is a boiler in which boiling water is kept. On the same side of the furnace, but outside it, is a large oval tub of a capacity of about 700 or 800 quarts, which is kept filled with water. The upper portions of the staves of this tub are covered with linen to absorb all parts that are spattered about.

«Powder for Gilding Metals.»—I.—In a solution of perchloride of gold soak small pieces of linen which are dried over the solution so that the drops falling therefrom are saved. When the rags are dry burn them, carefully gathering the ashes, which ashes, stirred with a little water, are used for gilding either with pumice stone or with a cork. For the hollows, use a small piece of soft wood, linden, or poplar.

II.—Dissolve the pure gold or the leaf in nitro-muriatic acid and then precipitate it by a piece of copper or by a solution of iron sulphate. The precipitate, if by copper, must be digested with distilled vinegar and then washed by pouring water over it repeatedly and dried. This precipitate will be in the form of very fine powder; it works better and is {580} more easily burnished than gold leaf ground with honey.

«Gilding Pastes.»—I.—A good gilding paste is prepared as follows: Slowly melt an ounce of pure lard over the fire, add 1/2 a teaspoonful of juice of squills, and stir up the mixture well, subsequently adding 10 drops of spirit of sal ammoniac. If the mixture is not stiff enough after cooling, the firmness may be enhanced by an admixture of 1/3 to 1/2 ounce of pure melted beef-tallow. A larger addition of tallow is necessary if the white of an egg is added. After each addition the mixture should be stirred up well and the white of egg should be added, not to the warm, but almost cold, mixture.

II.—Alum, 3 parts, by weight; saltpeter, 6 parts; sulphate of zinc, 3 parts; common salt, 3 parts. Mix all into a thick paste, dip the articles into it, and heat them, until nearly black, on a piece of sheet iron over a clear coke or charcoal fire; then plunge them into cold water.

«Red Gilding.»—This is obtained by the use of a mixture of equal parts of verdigris and powdered tartar, with which the article is coated; subsequently burning it off on a moderate coal fire. Cool in water, dip the article in a pickle of tartar, scratch it, and a handsome red shade will be the result, which has not attacked the gilding in any way.

«Regilding Mat Articles.»—In order to regenerate dead gold trinkets without having to color them again—which is, as a rule, impossible, because the gold is too weak to stand a second coloring—it is advisable to copper these articles over before gilding them. After the copper has deposited all over, the object, well cleaned and scratched, is hung in the gilding. By this manipulation much time and vexation is saved, such as every jeweler will have experienced in gilding mat gold articles. The article also acquires a faultless new appearance. Here are two recipes for the preparation of copper baths:

I.—Distilled boiling water, 2,000 parts, by weight; sodium sulphate, 10 parts; potassium cyanide, 15 parts; cupric acetate, 15 parts; sodium carbonate, 20 parts; ammonia, 12 parts.

II.—Dissolve crystallized verdigris, 20 parts, by weight, and potassium cyanide, 42 parts, in 1,000 parts of boiling water.

«Silk Gilding.»—This can only be accomplished by the electric process. The fiber is first rendered conductive by impregnation with silver nitrate solution and reduction of same with grape sugar and diluted alkali, or, best of all, with Raschig’s reduction salt. In place of the silver nitrate, a solution of lead acetate or copper acetate may be employed. The silk thus impregnated is treated in the solution of an alkaline sulphide, e. g., sodium sulphide, ammonium sulphide, or else with hydrogen sulphide, thus producing a conductive coating of metallic sulphide. Upon this gold can be precipitated by electrodeposition in the usual way.

«Spot Gilding.»—Gilding in spots, producing a very fine appearance, is done by putting a thin coat of oil on those parts of the metal where the gilding is not to appear; the gold will then be deposited in those spots only where there is no oil, and the oil is easily removed when the work is finished.

«Gilding Steel.»—Pure gold is dissolved in aqua regia; the solution is allowed to evaporate until the acid in excess has gone. The precipitate is placed in clean water, 3 times the quantity of sulphuric acid is added and the whole left to stand for 24 hours in a well-closed flask, until the ethereal gold solution floats on top. By moistening polished steel with the solution a very handsome gilding is obtained. By the application of designs with any desired varnish the appearance of a mixture of gold and steel may be imparted to the article.

«Wood Gilding.»—I.—The moldings, ledges, etc., to be gilded are painted with a strong solution of joiners’ glue, which is left to harden well, whereupon 8 to 10 coatings of glue mixed with whitening are given. Each coat must, of course, be thoroughly dry, before commencing the next. After this has been done, paint with a strong mixture of glue and minium, and while this is still wet, put on the gold leaflets and press them down with cotton. To impart the fine gloss, polish with a burnishing agate after the superfluous gold has been removed.

II.—Proceed as above, but take silver leaf instead of gold leaf, and after all is thoroughly dry and the superfluous silver has been removed, apply a coating of good gold lacquer. The effect will be equally satisfactory.

«Zinc Gilding.»—I.—Gilding by means of zinc contact may be accomplished with the following formula: Two parts, by weight, of gold chloride; 5 parts, by weight, of potassium cyanide; 10 parts, {581} by weight, of sulphite of soda; and 60 parts, by weight, of sodium phosphate are dissolved in 1,000 parts of water. When used the bath must be hot. A cold bath without the addition of potassium cyanide may also be used for gilding, and this consists of 7 parts, by weight, of gold chloride; 30 parts, by weight, of yellow prussiate of potash; 30 parts, by weight, of potash; 30 parts, by weight, of common salt in 1,000 parts of water.

II.—To gild zinc articles, dissolve 20 parts of gold chloride in 20 parts of distilled water, and 80 parts of potassium cyanide in 80 parts of water, mix the solutions, stir a few times, filter, and add tartar, 5 parts, and fine chalk, 100 parts. The resulting paste is applied with a brush. Objects of copper and brass are previously coated with zinc. This is done in the following manner: Heat a concentrated sal ammoniac solution to the boiling point with addition of zinc dust and immerse the thoroughly cleaned objects until a uniform zinc coating has formed. Or boil the articles in a concentrated caustic soda solution with zinc dust.

«OXIDIZING PROCESSES:»

«Aluminum Plating.»—I.—To plate iron and other metals with pure aluminum, deoxidize the pieces with a solution of borax and place them in an enameling oven, fitted for receiving metallic vapors. Raise the temperature to 1,832° to 2,732° F. Introduce the aluminum vapors generated by heating a quantity of the metal on the sand bath. When the vapors come in contact with the metallic surfaces, the aluminum is deposited. The vapors that have not been used or are exhausted may be conducted into a vessel of water.

«To Copper Aluminum», take

II.—Sulphate of copper 30 parts
Cream of tartar 30 parts
Soda 25 parts
Water 1,000 parts

The articles to be coppered are merely dipped in this bath, but they must be well cleaned previously.

«Antimony Baths.»—I.—By dissolving 15 parts, by weight, of tartar emetic and 15 parts of prepared tartar in 500 parts of hot water and adding 45–60 parts of hydrochloric acid and 45–60 parts of powdered antimony, brass becomes coated in the boiling liquid with beautiful antimony colors. In this manner it is possible to impart to brass golden, copper-red, violet, or bluish-gray shades, according to a shorter or longer stay of the objects in the liquid. These antimony colors possess a handsome luster, are permanent, and never change in the air.

II.—Carbonate of soda, 200 parts, by weight; sulphide of antimony, 50 parts; water, 1,000 parts. Heat the whole in a porcelain capsule for 1 hour, keeping constantly in ebullition; next, filter the solution, which, on cooling, leaves a precipitate, which boil again with the liquid for one-half hour, whereupon the bath is ready for use.

«To Coat Brass Articles with Antimony Colors.»—Dissolve 15 parts, by weight, of tartar emetic and 15 parts, by weight, of powdered tartar in 500 parts, by weight, of hot water and add 50 parts, by weight, of hydrochloric acid, and 50 parts, by weight, of powdered antimony. Into this mixture, heated to a boil, the immersed articles become covered with luster colors, a golden shade appearing at first, which is succeeded by one of copper red. If the objects remain longer in the liquid, the color passes into violet and finally into bluish gray.

«Brassing.»—I.—To brass small articles of iron or steel drop them into a quart of water and 1/2 ounce each of sulphate of copper and protochloride of tin. Stir the articles in this solution until desired color is obtained.

II.—Brassing Zinc, Steel, Cast Iron, etc.—Acetate of copper, 100 parts, by weight; cyanide of potassium, 250 parts; bisulphite of soda, 200 parts; liquid ammonia, 100 parts; protochloride of zinc, 80 parts; distilled water, 10,000 parts. Dissolve the cyanide of potassium and the bisulphite of soda. On the other hand, dissolve the ammonia in three-fourths of the water and the protochloride of zinc in the remaining water; next, mix the two solutions. This bath is excellent for brassing zinc and is used cold.

III.—Acetate of copper, 125 parts, by weight; cyanide of potassium, 400 parts; protochloride of zinc, 100 parts; liquid ammonia, 100 parts; distilled water, 8,000 to 10,000 parts. Proceed as above described.

IV.—Acetate of copper, 150 parts, by weight; carbonate of soda, 1,000 parts; cyanide of potassium, 550 parts; bisulphite of soda, 200 parts; protochloride of zinc, 100 parts. Proceed as above. This bath serves for iron, cast iron, and steel, and is used cold. {582}

«Colored Rings on Metal.»—Dissolve 200 parts, by weight, of caustic potash in 2,000 parts of water and add 50 parts of litharge. Boil this solution for half an hour, taking care that a little of the litharge remains undissolved. When cold, pour off the clear fluid; it is then ready for use. Move the object to and fro in the solution; a yellow-brown color appears, becoming in turn white, yellow, red, and finally a beautiful violet and blue. As soon as the desired color is obtained, remove the article quickly from the solution, rinse in clean water, and dry in sawdust.

«Green or Gold Color for Brass.»—French articles of brass, both cast and made of sheet brass, mostly exhibit a golden color, which is produced by a copper coating. This color is prepared as follows: Dissolve 50 parts, by weight, of caustic soda and 40 parts of milk sugar in 1,000 parts of water and boil a quarter of an hour. The solution finally acquires a dark-yellow color. Now add to the mixture, which is removed from the fire, 40 parts of concentrated cold blue vitriol solution. A red precipitate is obtained from the vitriol, which falls to the bottom at 167° F. Next a wooden sieve, fitted to the vessel, is put into the liquid with the polished brass articles. Toward the end of the second minute the golden color is usually dark enough. The sieve with the articles is taken out and the latter are washed and dried in sawdust. If they remain in the copper solution they soon assume a green color, which in a short time passes into yellow and bluish green, and finally into the iridescent colors. These shades must be produced slowly at a temperature of 133° to 135° F.

«To Give a Green Color to Gold Jewelry.»—Take verdigris, 120 parts, by weight; sal ammoniac, 120 parts; nitrate of potassium, 45 parts; sulphate of zinc, 16 parts. Grind the whole and mix with strong vinegar. Place on the fire and boil in it the articles to be colored.

«Nickeling by Oxidation.»—I.—Nickeling may be performed on all metals cold, by means of nickelene by the Mitressey process, without employing electrical apparatus, and any desired thickness deposited. It is said to be more solid than nickel.

First Bath.—Clean the objects and take 5 parts, by weight, of American potash per 25 parts, by weight, of water. If the pieces are quite rusted, take 2 parts, by weight, of chlorhydric acid per 1 part, by weight, of water. The bath is employed cold.

Second Bath.—Put 250 parts, by weight, of sulphate of copper in 25,000 parts, by weight, of water. After dissolution add a few drops of sulphuric acid, drop by drop, stirring the liquid with a wooden stick until it becomes as clear as spring water.

Take out the pieces thus cleaned and place them in what is called the copper bath, attaching to them leaves of zinc; they will assume a red tint. Then pass them into the nickeling bath, which is thus composed:

By weight Cream of tartar 20 parts Sal ammoniac, in powder 10 parts Kitchen salt 5 parts Oxychlorhydrate of tin 20 parts Sulphate of nickel, single 30 parts Sulphate of nickel, double 50 parts

Remove the pieces from the bath in a few minutes and rub them with fine sand on a moist rag. Brilliancy will thus be obtained. To improve the appearance, apply a brass wire brush. The nickeling is said to be more solid and beautiful than that obtained by the electrical method.

Brilliancy may be also imparted by means of a piece of buff glued on a wooden wheel and smeared with English red stuff. This will give a glazed appearance.

II.—Prepare a bath of neutral zinc chloride and a neutral solution of a nickel salt. The objects are immersed in the bath with small pieces of zinc and kept boiling for some time. This process has given satisfactory results. It is easy to prepare the zinc chloride by dissolving it in hydrochloric acid, as well as a saturated solution of ammoniacal nickel sulphate in the proportion of two volumes of the latter to one of the zinc chloride. The objects should be boiled for 15 minutes in the bath. Nickel salt may also be employed, preferably in the state of chloride.

«Pickling Solutions.»—Oxidized copper, brass, and German silver articles must be cleansed by acid solutions. In the case of brass alloys, this process, through which the object acquires a dull yellow surface, is known as dipping or yellowing. The treatment consists of {583} several successive operations. The article is first boiled in a lye composed of 1 part caustic soda and 10 parts water, or in a solution of potash or soda or in limewater; small objects may be placed in alcohol or benzine. When all the grease has been removed, the article is well rinsed with water, and is then ready for the next pickling. It is first plunged into a mixture of 1 part sulphuric acid and 10 parts water, and allowed to remain in it till it acquires a reddish tinge. It is then immersed in 40° Bé. nitric acid, for the purpose of removing the red tinge, and then for a few seconds into a bath of 1 part nitric acid, 1.25 parts sulphuric acid of 66° Bé., 0.01 part common salt, and 0.02 parts lampblack. The article must then be immediately and carefully washed with water till no trace of acid remains. It is then ready for galvanizing or drying in bran or beech sawdust. When articles united with soft solder are pickled in nitric acid, the solder receives a gray-black color.

«Palladiumizing Watch Movements.»—Palladium is successfully employed for coating parts of timepieces and other pieces of metals to preserve them against oxidation. To prepare a palladium bath use the following ingredients: Chloride of palladium, 10 parts, by weight; phosphate of ammonia, 100 parts; phosphate of soda, 300 parts; benzoic acid, 8 parts; water, 2,000 parts.

«Metal Browning by Oxidation.»—The article ought first to be cleaned with either nitric acid or muriatic acid, then immersed in an acid affecting the metal and dried in a warm place. A light coating is thus formed. For a second coating acetic or formic acid is used preferably for aluminum, nickel, and copper; but for iron and steel, muriatic or nitric acid. After cleaning, the article is placed in a solution of tannin or gallic acid, and is then dried in a warm place as before. The second coating is of a yellowish-brown color. On placing it near the fire, the color can be deepened until it becomes completely black; care must be taken to withdraw it when the desired shade is produced. Instead of the acids employed for the first coating, ammonia may be used.

«Silvering by Oxidation.»—The oxidizing of silver darkens it, and gives an antique appearance that is highly prized.

I.—The salts of silver are colorless when the acids, the elements of which enter into their composition, are not colored, but they generally blacken on exposure to light. It is easy, therefore, to blacken silver and obtain its oxide; it is sufficient to place it in contact with a sulphide, vapor of sulphur, sulphohydric acids, such as the sulphides or polysulphides of potash, soda, dissolved in water and called _eau de barège_. The chlorides play the same part, and the chloride of lime in solution or simply Javelle water may be used. It is used hot in order to accelerate its action. The bath must be prepared new for each operation for two reasons: (1) It is of little value; (2) the sulphides precipitate rapidly and give best effects only at the time of their direct precipitations. The quantity of the reagent in solution, forming the bath, depends upon the thickness of the deposit of silver. When this is trifling, the oxidation penetrates the entire deposit and the silver exfoliates in smaller scales, leaving the copper bare. It is necessary, therefore, in this case to operate with dilute baths inclosing only about 45 grains of oxidizant at most per quart. The operation is simple: Heat the necessary quantity of water, add the sulphide or chloride and agitate to effect the solution of the mixture, and then at once plunge in the silver-plated articles, leaving them immersed only for a few seconds, which exposure is sufficient to cover it with a pellicle of deep black-blue silver. After withdrawing they are plunged in clean cold water, rinsed and dried, and either left mat or else polished, according to the nature of the articles.

Should the result not be satisfactory, the articles are brightened by immersing them in a lukewarm solution of cyanide of potassium. The oxide, the true name of which would be the sulphuret or chloruret, can be raised only on an object either entirely of silver or silver plated.

II.—Rub the article with a mixture of graphite, 6 parts, and powdered bloodstone, 1 part, moistened with oil of turpentine. Allow to dry and brush with soft brushes passed over wax. Or else, brush with a soft brush wet with alcoholic or aqueous platinic chloride solution of 1 in 20.

III.—Sulphurizing is effected with the following methods: Dip in a solution heated to about 175° F., of potassium sulphide, 5 parts, by weight; ammonium carbonate, 10 parts; water, 1,000 parts; or, calcium sulphide, 1 to 2 parts; sal ammoniac, 4 parts; water, 1,000 parts. {584}

IV.—In the following solution articles of silver obtain a warm brown tone: Copper sulphate, 20 parts, by weight; potassium nitrate, 10 parts; ammonium chloride, 20 parts. By means of bromine, silver and silver alloys receive a black coloring. On engraved surfaces a niello-like effect may be produced thereby.

«Oxidized Steel.»—I.—Mix together bismuth chloride, 1 part; mercury bichloride, 2 parts; copper chloride, 1 part; hydrochloric acid, 6 parts; alcohol, 5 parts; and water, 5 parts. To use this mixture successfully the articles to be oxidized must be cleaned perfectly and freed from all grease, which is best accomplished by boiling them in a soda solution or by washing in spirit of wine. Care should be taken not to touch the article with the fingers again after this cleaning. However clean the hand may be, it always has grease on it and leaves spots after touching, especially on steel. Next the object is dipped into the liquid, or if this is not possible the solution is applied thin but evenly with a brush, pencil, or rabbit’s foot. When the liquid has dried, the article is placed for a half hour in simple boiling water. If a very dark shade is desired the process is repeated until the required color is attained.

II.—Apply, by means of a sponge, a solution of crystallized iron chloride, 2 parts; solid butter of antimony, 2 parts; and gallic acid, 1 part in 5 parts of water. Dry the article in the air and repeat the treatment until the desired shade is reached. Finally rinse with water, dry, and rub with linseed-oil varnish.

«Tinning by Oxidation.»—A dipping bath for tinning iron is prepared by dissolving 300 parts, by weight, ammonia alum (sulphate of alumina and sulphate of ammonia) and 10 parts of melted stannous chloride (tin salt) in 20,000 parts of warm water. As soon as the solution boils, the iron articles, previously pickled and rinsed in fresh water, are plunged into the fluid; they are immediately covered with a layer of tin of a beautiful dull-white color, which can be made bright by treatment in a tub or sack. Small quantities of tin salt are added from time to time as may be required to replace the tin deposited on the iron. This bath is also well adapted for tinning zinc, but here also, as with iron, the deposit is not sufficient to prevent oxidation of the metal below. Larger articles tinned in this way are polished by scratch brushing. In tinning zinc by this process, the ammonia alum may be replaced by any other kind of alum, or aluminum sulphate may be used alone; experience has shown, however, that this cannot be done with iron, cast iron, or steel. If it is desired to tin other metals besides iron and zinc in the solution which we have described, the battery must be resorted to; if the latter is used, the above solution should be applied in preference to any other.

«PATINA OXIDIZING PROCESSES:»

«Patina of Art Bronzes.»—For all patinas, whether the ordinary brown of commerce, the green of the Barye bronzes, or the dark-orange tint of the Florentine bronzes, a brush is used with pigments varying according to the shade desired and applied to the metal after it is warmed. Recipes are to be met with on every hand that have not been patented. But the details of the operation are the important thing, and often the effect is produced by a handicraft which it is difficult to penetrate.

I.—A dark tint may be obtained by cleaning the object and applying a coat of hydrosulphate of ammonia; then, after drying it, by rubbing with a brush smeared with red chalk and plumbago. The copper may also be moistened with a dilute solution of chloride of platina and warmed slightly, or still by plunging it in a warm solution of the hydrochlorate of antimony. For the verde antique a solution is recommended composed of 200 grams of acetic acid of 8° strength, the same quantity of common vinegar, 30 parts, by weight, of carbonate of ammonia; 10 parts, by weight, of sea salt; with the same quantities of cream of tartar and acetate of copper and a little water. To obtain the bronze of medals several processes afford a selection: For example, the piece may be dipped in a bath consisting of equal parts of the perchloride and the sesquiazotate of iron, warming to the evaporation of the liquid, and rubbing with a waxed brush.

II.—Dissolve copper nitrate, 10 parts, by weight, and kitchen salt, 2 parts, in 500 parts of water and add a solution of ammonium acetate obtained by neutralization of 10 parts of officinal spirit of sal ammoniac with acetic acid to a faintly acid reaction, and filling up with water to 500 parts. Immerse the bronze, allow to dry, brush off superficially and repeat this until the desired shade of color has been obtained. {585}

«A Permanent Patina for Copper.»—

Green.—

I.—Sodium chloride 37 parts
Ammonia water 75 parts
Ammonium chloride 37 parts
Strong wine vinegar 5,000 parts

Mix and dissolve. Apply to object to be treated, with a camel’s-hair pencil. Repeat the operation until the desired shade of green is reached.

Yellow Green.—

II.—Oxalic acid 5 parts
Ammonium chloride 10 parts
Acetic acid, 30 per cent dilution 500 parts

Mix and dissolve. Use as above indicated. The following will produce the same result:

III.—Potassium oxalate, acid 4 parts
Ammonium chloride 16–17 parts
Vinegar containing 6 per cent of acetic acid 1,000 parts

IV.—Bluish Green.—After using the first formula (for green) pencil over with the following solution:

Ammonium chloride 40 parts Ammonium carbonate 120 parts Water 1,000 parts

Mix and dissolve.

Greenish Brown.—

V.—Potassium sulphuret 5 parts
Water 1,000 parts

Mix and dissolve. With this, pencil over object to be treated, let dry, then pencil over with 10 parts a mixture of a saturated solution of ammonia water and acetic acid and 5 parts of ammonium chloride thinned with 1,000 parts of water. Let dry again, then brush off well. Repeat, if necessary, until the desired hue is attained.

Another Blue Green.—

VI.—Corrosive sublimate 25 parts
Potassium nitrate 86 parts
Borax 56 parts
Zinc oxide 113 parts
Copper acetate 220–225 parts

Mix and heat together on the surface of the object under treatment.

VII.—Brown.—The following is a Parisian method of producing a beautiful deep brown:

Potassium oxalate, acid 3 parts Ammonium chloride 15 parts Water, distilled 280 parts

Mix and dissolve. The object is penciled over with this several times, each time allowing the solution to dry before putting on any more. The process is slow, but makes an elegant finish.

«Green Patina Upon Copper.»—To produce a green patina upon copper take tartaric acid, dilute it half and half with boiling water; coat the copper with this; allow to dry for one day and rub the applied layer off again the next day with oakum. The coating must be done in dry weather, else no success will be obtained. Take hydrochloric acid and dilute it half and half with boiling water, but the hydrochloric acid should be poured in the water, not vice-versa, which is dangerous. In this hydrochloric acid water dissolve as much zinc as it can solve and allow to settle. The clear liquid is again diluted half with boiling water and the copper is coated with this a few times.

«Black Patina.»—Black patina is obtained by coating with tallow the pieces to be oxidized and lighting with a rosin torch. Finally, wipe the reliefs and let dry.

«Blue-Black Patina.»—Use a dilute solution of chloride of antimony in water and add a little free hydrochloric acid. Apply with a soft brush, allow the article to dry and rub with a flannel. If expense is no object, employ a solution of chloride of palladium, which gives a magnificent blue black. It is necessary, however, to previously clean the articles thoroughly in a hot solution of carbonate of soda, in order to remove the dirt and greasy matter, which would prevent the patina from becoming fixed.

«Red Patina.»—The following is a new method of making a red patina, the so-called blood bronze, on copper and copper alloys. The metallic object is first made red hot, whereby it becomes covered with a coating consisting of cupric oxide on the surface and cuprous oxide beneath. After cooling, it is worked upon with a polishing plate until the black cupric oxide coating is removed and the cuprous oxide appears. The metal now shows an intense red color, {586} with a considerable degree of luster, both of which are so permanent that it can be treated with chemicals, such as blue vitriol, for instance, without being in the least affected.

If it is desired to produce a marbled surface, instead of an even red color, borax or some chemical having a similar action is sprinkled upon the metal during the process of heating. On the places covered by the borax, oxidation is prevented, and after polishing, spots of the original metallic color will appear in the red surface. These can be colored by well-known processes, so as to give the desired marbled appearance.

«PLATINIZING:»