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cleansing operations; - A furnace and soda crystals, which prevents the action separate pans for first dipping, old aqua- | of the acid upon the silver. Then place fortis, aquafortis and soot, compound acids the article between layers of dry and for dead lustre, compound acids for bright warm fir wood saw-dust, which will ablustre, solution of nitrate of mercury, sorb the saline solution. Nitric, instead acids to dissolve gold from old pieces, of sulphuric, acid may be used for the acids to dissolve silver from old pieces ; pickle bath. In this case, the water must with two large pans for rinsing with a be distilled, and the acid free from chloconstant flow of water. If the draught of rine or hydrochloric acid, otherwise the the chimney is not sufficient, a small fire silverware will be covered with a bluishmay be kindled under the hood. A gas white film of chloride of silver This burner is often sufficient. The pot of method will not suit articles in which nitrate of mercury, with two rinsing pans, iron or zinc may be present. In such may be placed near the electroplating cases, employ alkalies, and polish afterbath.
wards with very fine sand or pumice-dust, CLEANSING SILVER. — Mechanical with the aid of a stiff and short brush, or agents will not, like acids, act simulta- with a scratch-brush alone. Perfectly neously on every part of the object, and cleansed silver may directly receive a it is impossible to entirely prevent the metallic deposit which will have the same action of the air, steam, gases, and acid dead lustre as the object itself, but it is fumes. Heat the object to a dull red heat customary, before introducing the articles upon a slow fire. If the silver is pure, it into the electroplating bath, to scratch. becomes covered with a thin bluish film; | brush them, but if, as is nearly always the case, the SCRATCII-BRUSHING.-Scratch-brushsilver is alloyed with a variable propor- ing is to remove the dead lustre on an tion of copper, the latter becomes oxidized, object by the frequently-repeated friction and covers the piece with a greyish-black of the points of many stiff and straight coating. While the piece is still hot, metallic wires, called a scratch-brush or plunge it into a boiling pickle of water | wire-brush. Its shape varies with the and sulphuric acid, which dissolves the | articles to be operated upon. A hand oxide. If the heat has been sufficiently scratch-brush is made of numerous wires, protracted for oxidizing all the copper stiff and straight, taken from a bundle or on the surface, the object, when removed coil of large diameter, so that the wires from the pickle, is of a perfectly dead have little tendency to curve. For deliwhite. It is greyish if the heating has cate objects, scratch-brushes are made of been too short, and the operation must be spun glass, the fibres of which are very repeated as many times as are needed for a thin and elastic. For making a good hand perfect lustre. Or the silver may be scratch-brush, choose a bundle or coil of placed in sheet-iron boxes filled with a brass wire of the proper thickness, and mixture of powdered borax, lime, and wrap a good string tightly round it for charcoal dust. The borax dissolves the about two-thirds of the intended length oxide of copper as soon as formed. If the of the instrument, usually about 8 inches. objects to be cleansed are hollow, it is Then, with a cold chisel, cut the bundle necessary, before heating, to make a small of wire close to the string at one end, and hole which will allow of the escape of the at 2 inches from the other end of the air expanded by the fire. Without this string wrapping. Dip the end closed by precaution, the piece will burst open. the string into a neutral solution of chloWhen the piece is put into the pickle, the ride of zinc, and plunge into melted acid liquor enters through the hole, and tin, which solders all the wires, and takes the place of the air between the prevents their separation and injury shells, and is difficult to remove. In order to the hand of the operator. The tool is to prevent the spotting of the piece by this then fixed to a thin wooden handle which liquor, it is dipped for a few minutes into projects above the soldered end. Very a very dilute solution of ammonia or of small scratch-brushes are necessary for reaching small holes and corners. An which a slender jet of water runs upon old scratch-brush, the wires of which the brush. A board receives the projected nave been bent in every direction, and water, and lets it fall into a zinc pau fixed to a long handle, is useful for rub-resting on the bottom of the box. bing the insides of certain pieces, such as Scratch-brushes.—The brass wire used Etruscan vases. Scratch-brushing is sel- for the manufacture of hand or circular dom done dry; the tool and pieces must scratch-brushes is of various strengths. be constantly wetted with a stream of Thick wires are employed for bronzes, water, which carries away the impu- and thinner wires for lighter articles. rities. Good metallic deposits are only The wires must be preserved stiff and polished by the friction of the scratch-straight. When a hand scratch-brush brush; bad ones scale off from the defec- becomes too short, cut the twisted ends tive adhesion. A large tub, with a board with a cold chisel, and a new portion of placed across it, on which to rest the wire is uncovered by removing part of pieces, may be used ; and various solutions the string wrapping. To remove the are employed to assist the brushing, such twisted wire ends, rest the scratch-brush as water and vinegar, or sour wine, upon a lead block, and cut them with a or solutions of cream of tartar or alum, sharp cold chisel, with one stroke of a when it is desired to brighten a gold hammer if possible. When they begin deposit which is too dark; but generally to curl, they are now and then beaten a decoction of liquorice-root, horse-chest- with a mallet of boxwood, upon a small nut, marsh mallow, or bark of Panama block kept between the knees, so as not to wood, all of which allow of a gentle rub-produce a dead stroke. Scratch-brushes bing with the scratch-brush, with the if kept too long in water become hard ; production of an abundant scum. Every when greasy, they are cleansed in caustic 5 or 6 days the old liquid is carefully potash; oxide is removed by the compound decanted, so as not to carry away the acids. This last operation, and even dipdeposits at the bottom, which always con- ping in aquafortis, are sometimes resorted tain some of the precious metals, which to for diminishing the size of the wires, are collected to be afterwards treated and making them smoother. The circular For small objects and articles of jewel-brush is occasionally resorted to for dimi. lery, hold the scratch-brush as a writing nishing the size of the wires, and making pen, and the motior is imparted by the them smoother. The circular brush is wrist only, the forearm resting on the edge occasionally reversed, in order to change of the tub. For larger articles of bronze, the direction of the wires. hold the fingers extended close to the Bright Lustre for small Articles.-Very fore part of the scratch-brush, so as to small articles, which cannot be scratchmaintain the wires, and, with raised brushed, receive a bright lustre by muelbow, strike the piece repeatedly with a tual friction. The operation is generally sliding motion at the same time. When performed with the hands. The articles a hollow is met which cannot be rubbed to be brightened are introduced, together lengthways, a twisting motion is given with boxwood saw-dust, bran, or sand, to the tool. Circular wire-brushes, fixed into a bag; the ends of the bag being on the spindle of a lathe, and the wires gathered into the hands with the thumbs of which move all in the same direction, inwards, the bag is shaken to and fro. have been constructed for certain pieces As this operation becomes very fatiguing, of silversmith work, such as forks and mechanical means may be employed to spoons.
effect the shaking. Lathe for Scratch-brush.-An ordinary CLEANSING ZINC.—Zinc is cleansed by lathe is used for scratch-brushing, upon being passed through a boiling solution the spindle of which is fixed a circular of caustic lye, without remaining too long brush of brass wires. A wooden frame in it, because it may be corroded, and covers the wire brush; it is open in front; | even dissolved; after rinsing, it is plunged the top supports a small reservoir from | for a few minutes into water containing from one-tenth to one-twentieth of or brass is interposed between the low sulphuric acid, then rinsed in plenty of metal, and the gold or silver. warm water, and, when necessary, brushed CLEANSING CAST IRON.-Cast iron is with a stiff brush and pumice-stone dust, cleansed by being immersed for 2 or 3 or seratch-brushed. This last operation hours in water containing one-hundredth is especially useful when parts have been part of sulphuric acid; the metal is afterunited with tin solder, which becomes wards rinsed in cold water, and scoured black and dull by the a!kaline and acid with sharp sand and a fibre brush, or a baths. Another method is to dip the coarse rag; then put again in the acid articles rapidly into a cold mixture of pickle, rinsed, and plunged into the elecsulphuric acid, 100 parts; nitric acid, tro bath. If more than 1 per cent, of 100; common salt, 1 per cent.; and sulphuric acid is added to the water, the quickly rinse in cold water perfectly free length of the immersion must be shortfrom copper salt, which will blacken the ened, otherwise the cast iron will be zinc. If, instead of quickly cleansing the deeply corroded, and the carbon of the zinc, it is allowed to remain a little longer metal, which is insoluble in the pickle, in the mixture, it acquires a dead lustre will with great difficulty be removed by which may be utilized for producing con- | the friction of the sand. Cast iron does trasts between the various parts of the not gild or silver well, by a direct deposit same ornament. The dead lustre will of the precious metals. Copper or brass become a bright one, if the object is deposits are better, although far from quickly plunged in several times, and perfect; but if cast iron is tinned, the rinsed as often, in the same compound coat is adherent, and will afterwards acids. It often happens that the lines of receive copper, brass, gold, or silver, if tin or lead solder are black after being desired. If it is desired to keep cast iron dipped into the acid bath; it is then already cleansed for some time before sufficient to scratch-brush before placing electroplating it, it is necessary to prethe object in the electroplating solution. serve it in a liquor rendered alkaline by Zinc may be slightly amalgamated with caustic lime, potash, or soda, or their the solution of nitrate of binoxide of mer- carbonates; but caustic lime-water is the cury; this increases the adherence of the cheapest and most easy method, and cast electro deposits. It is often necessary, | iron which has remained in it for a few from some defect in cleansing, or in elec- hours will not rust after a long exposure troplating, which impairs the adherence to a damp atmosphere. of the deposits, to do the work over again. CLEANSING WROUGHT IRON. — The In such a case, remove the copper entirely cleansing of wrought iron is effected in by plunging the object into aquafortis the same manner as cast iron, but will and soot, until it appears black. Another bear a stronger pickle and a longer imdipping into the compound acids will mersion. We refer in this place to ordirender it perfectly clean and white, and nary wrought iron covered with a film of ready to receive a new deposit.
black magnetic scale or of red rust. CLEANSING LEAD AND TIN.—Tin, lead, Whitened, filed, or polished iron must be and the alloys of these metals, are much treated like steel. more difficult to cleanse than zinc. A CLEANSING STEEL.-Polished articles rapid scouring with potash lye, and a of steel, or iron, must be first cleansed rubbing with a hard substance are the in a boiling solution of caustic lye, and only means of effecting this. The objects rubbed with pumice-stone dust, which are sometimes plunged into diluted by- scratches the polish slightly, and thus drochloric acid; but the first operation produces a better hold for the metals is nearly always necessary. Notwith- | afterwards to be deposited. They are standing the greatest care, the direct then rapidly passed through a bath comdeposit of the precious metals is difficult, | posed of water, 1 quart; hydrochloric and does not adhere well. The results acid, 12 oz.; or sulphuric acid, 4 oz.; are much better if a coat of pure copper 'rinsed in cold water, and plunged into the electroplating solution. Carefully | Daniell's elements only is used, which avoid substituting nitric acid for the hy- seldom happens, on account of the feeble drochloric or sulphuric acid, of the above intensity of the current, the conducting acid bath. Iron and steel may be well wire which supports the article to be gilt, without an intermediary coat, in galvanized is connected with the zinc hot' gilding baths. Silvering directly piate by a binding screw of brass, and upon steel or iron is always imperfect the other wire supporting the anode is and without adherence; it is therefore connected with the copper of the excustomary to interpose a coat of copper terior vase. The solution of sulphate of or brass, which renders the further opera copper must be kept constantly satution of silver plating easy.
rated with crystals of this salt, enclosed GALVANIC BATTERIES.—There are two is a bag of linen or hair cloth. A simi. kinds of batteries used for electro-depo lar process may be employed to keep the sition; those which act under the action solution of common salt in a state of of physical agents; but these, on account saturation. A battery thus arranged of their feeble intensity, are rarely used. may be kept in operation for three weeks, Others act under the influence of chemi or a month. When this battery is work cal reactions, of decompositions and re ing, the copper of the decomposed sulcompositions, or of greater or less affi phate is deposited upon the copper of the nities. The varieties of these instruments vessel, which thus increases in weight are, at the present time, very numerous. and in value. The zinc is slowly disBut the best battery is that which, under solved in the solution of common salt, the smallest volume, is the most ener and forms a double chloride of sodium getic, constant, regular, and economical. and zinc. When a number of the ele
Daniell's Battery. This battery de ments of a Daniell's battery are to be velops a constant and lasting current, joined together, the zinc of the first elebut is wanting in intensity. It is especi ment is connected with the copper of the ally adapted to slow deposits, which second by means of a well-cleansed must be thick and of uniform texture. metallic ribbon, then the zinc of the A great advantage of this battery is, second with the copper of the third, and that it will work without acids, and so on, until the whole apparatus presents therefore without the production of at one end a copper vase, and at the gases or smell, and can be used in a other a zinc plate, unconnected. A private apartment without inconveni- metallic wire connects the anode with ence. The vase for the battery is a flat the copper end, and a similar wire is vessel of pure copper, which is half filled bound to the zinc end, and supports the with a saturated solution of sulphate of object to be electroplated. Another batcopper, into which is placed a bag of tery used by the electro-gilders of watch canvas or a cell of porous procelain or parts and by telegraphers, is composed earthenware, which causes the solution of a cylindrical vase of stoneware, of sulphate of copper to rise to about glass, or porcelain ; a cylinder of zinc to 1 in. from the top of the copper vessel. which is soldered a ribbon of pure copThe bag or cell is filled with a saturated per; a porous clay cell, and a glass balsolution of common salt, in which a loon with a short neck, and filed with well-cleansed zinc plate is placed. It is crystals of sulphate of copper. It is necessary that the levels of the two closed with a cork perforated with two solutions should be nearly the same. If holes, or having two notches cut along there is any difference, the solution of its sides. The rolled zinc plate is put chloride of sodium should be slightly l into the stoneware pot, and the porous above the other, because if the solution cell inside the zinc. The copper ribbon of sulphate of copper passes into the of the zinc of the first element dips on porous cell, the zinc is immediately cor- to the bottom of the cell of the next roded, and blackened, and the battery element, in such a manner that, when may cease to work. When one of several elements are connected together,
there is at one end the ribbon of a zinc salt, to the water in which the ziuc is plate, and at the other end a copper rib- | placed. bon put into the cell. Then the porous Bunsen's Battery.-Each element is cell and the stoneware pot are filled to composed of a glass vessel which is half the same level with water. The balloon filled with nitric acid at 36° or 40° containing the crystallized sulphate of Baumé, and which receives a hollow copper receives as much water as it can cylinder of pulverized coke, moulded and hold, and the notched cork being put in cemented at a high temperature, by place, the balloon is quickly inverted sugar, gum, or tar. At the upper part with its neck in the water of the porous of this cylinder, where it does not dip cell. The battery is ready to work into the acid, a copper collar is fixed, 24 hours after. The ribbon of the zinc which may be tightened at will by means end is connected with the objects to be of a screw. A copper band or ribbon is electroplated, and that of the other cell | fixed to the collar, and may be connected end, with the soluble anode. The sul- with the zinc of another element. A phate of copper contained in the bal- | porous porcelain cell is placed inside the loon is dissolved in the water around it, coke cylinder, and contains a diluted and as this solution is denser than water solution of sulphuric acid, 1 part acid it falls into the porous cells through one and 9 parts water, into which is put a of the notches of the cork, while an bar or cylinder of zinc strongly amalgaequal quantity of purer and lighter mated, or covered with mercury. When water ascends through the other notch, a battery of several elements is to be and so on, producing a circuit of denser formed, the coke of the first element is liquor falling by one notch, and of lighter connected with the zinc of the second, liquor rising by the other. The solution and so on, and the apparatus is completed, of sulphate of copper is decomposed in at one end, by coke communicating with the porous cell; the sulphuric acid the anode, and at the other, by a zinc passes through the cell by outward pres- connected with the cathode, or object to sure and acts upon the zinc, and at the be electroplated. In this apparatus the same time the copper becomes deposited surface of the carbon is much greater upon the copper ribbon connected with than that of the zinc; this is a wrong the zinc of the former element. In order disposition, since, generally, the intensity that this battery may work regularly of the current is in direct ratio with the for 6 or 7 months, it is sufficient to surface of the zinc corroded, provided replace the evaporated water. The that this surface be opposite and parallel balloon ought to contain at least 2 lbs. to that of the carbon. of sulphate of copper, and the zinc to be | Bunsen's Battery modified by Arche about 7 in. in height, and from 4 to 4} in. reau.—This battery is preferred by gold in diameter. I'ne zinc may be amalga- and silver electroplaters. Each element mated, in which case the action is a little is composed of an exterior vessel or slow at the start, but more regular pot, most generally of stoneware ; a afterwards. The copper ribbon receives cylinder of zinc, covered with mercury, all the metal of the decomposed sulphate, provided with a binding screw, or with and it sometimes happens that part of a copper band, whether for a single the copper becomes deposited upon the element, or for the end of a combination porous cell, which must then be cleaned of elements in a battery, or to connect in aquafortis. When all the sulphate of the zinc with the carbon of another copper is used up, the balloons are filled element. A porous cell of earthenware with a fresh quantity of crystals and pipe or porcelain. A cylinder of granew copper ribbons inserted to take the phite, made from the residue found in place of those rendered too voluminous. old gas retorts. The graphite is bound if it be desired to start the battery by a copper band fixed to it by means of with a balloon immediately, add a small a wire of the same metal, all the bind. quantity of sulphuric acid, or of common | ing being afterwards covered with a