;fiv^' una Edited House P/ Co7ite used by Whitewa Embellis Boot IV Fi Conte Re-Welti Stitching and Shoe Howtc am Coftte writer's ( Forms o Ticket-\\ Wood Wi Conte. French P Off. Gla2 and Revi Piocesses oi varn^sning vvooa vamisITes. Dynamos and Electric Motors. Qass Book ^'"^"0 lES f "Work. APERHANGING, has, etc. Tools ipera Painting, sering a Room. Lasting, and ots and Shoes. Sewing and Riveted Boots 70 Engravings . The Sign- The Simpler a Signboard. id Polishing. aining Wood. , and Spiriting Re-polishing Floors Stains. Ke-pblisRing STiop Fronts. With 142 Engravings and Diagrams Contents. — Introduction. Siemens Dynamo. Gramme Dynamo. Manchester Dynamo. Simplex Dynamo. Calculating the Size and Amount of Wire for Small Dynamos. Ailments of Small Dynamo Electric Machines : their Causes and Cures. Small Electro-motors without Castings. How to Determine the Direction of Rotation of a Motor. How to Make a Shutt'e-Armature Motor. Undertype 50- Watt Dynamo. Manchester Type 440- Watt Dynamo. Cycle Building: and Repairing. With 142 Engravings and Diagrams. Contents. — Introductory, and Tools Used. How to Build a Front Driver. Building a Rear-driving Safety. Building Tandem Safeties. Building Front- driver Tricycle. Building a Hand Tricycle. Brazing. How to Make and Fit Gear Cases. Fittings and Accessories. Wheel Making. Tyres and Methods of Fixing them. Enamelling. Repairing. Decorative Desigrns of All Ag^es for All Purposes. With 277 Engravings and Diagrams. Contents. — Savage Ornament. Egyptian Ornament. Assyrian Ornament. Greek Ornament. Roman Ornament. Early Christian Ornament. Arabic Ornament. Celtic and Scandinavian Ornaments. Mediaeval Ornament. Renascence and Modern Ornaments. Chinese Ornament. Persian Ornament. Indian Ornament. Japanese Ornament. Mounting and Framing Pictures. With 240 Engravings, etc. Contents.— Making Picture Frames. Notes onArt Frames. Picture Frame Cramps. Making Oxford Frames. Gilding Picture Frames. Methods of Mounting Pictures. Making Photograph Frames. Frames covered with Plush and Cork. Hanging and Packing Pictures. Smiths' Work. With 211 Engravings and Diagrams. C^«z'^;/2'\.— Forges and Appliances. Hand Tools. Drawing Down and Up- setting. Welding and Punching. Conditions of Work : Principles of Forma- tion. Bending and Ring Making. Miscellaneous Examples of Forged Work. Cranks, Model Work, and Die Forging. Home-made Forges. The Manipula- tion of Steel at the Forge. (Continued on next page.) DAVID McKAY, Publisher, 1022 Market Street, Philadelphia. HANDICRAFT SERIES {continued). Glass Working by Heat and Abrasion. With 300 Engravings and Diagrams. Contents. — Appliances used in Glass Blowing. Manipulating Glass Tubing. Blowing Bulbs and Flasks. Jointing Tubes to Bulbs forming Thistle Funnels, etc. Blowing and Etching Glass Fancy Articles ; Embossing and Gilding Flat Surfaces. Utilising Broken Glass Apparatus ; Boring Holes in, and Riveting Glass. Hand-working of Telescope Specula. Turning, Chipping, and Grinding Glass. The Manufacture of Glass. Building: Model Boats. With 168 Engravings and Diagrams. Contents.— '^KViX^xaZ Model Yachts. Rigging and Sailing Model Yachts. Making and Fitting Simple Model Boats. Building a Model Atlantic Liner. Vertical Engine for a Model Launch. Model Launch Engine with Reversing Gear, Making a Show Case for a Model Boat. Electric Bells, How to Make and Fit Them. With 162 En- graving s and Diagrams. Contents. — The Electr c Current and the Laws that Govern it. Current Conductors used in Electric-Bell Work. Wiring for Electric Bells. Elaborated Systems of Wiring ; Burglar Alarms. Batteries for Electric Bells. The Con- struction of Electric Bells, Pushes, and Switches. Indicators for Electric-Bell Systems. Bamboo Work. With 177 Engravings and Diagrams. Contents. — Bamboo ; Its Sources and Uses. How to Work Bamboo. Bamboo Tables. Bamboo Chairs and Seats. Bamboo Bedroom Furniture. Bamboo Hall Racks and Stands. Bamboo Music Racks. Bamboo Cabinets and Book- cases. Bamboo Window Blinds. Miscellaneous Articles of Bamboo. Bamboo Mail Cart. Taxidermy. With 108 Engravings and Diagrams. Contents. — 'SiV\x\vi\v\'g Birds. St.ffmg and Mounting Birds. Skinning and Stuffing Mammals. Mounting Animals' Horned Heads : Polishing and Mount- ing Horns. Skinning, Stuffing, and Casting Fish. Preserving, Cleaning, and Dyeing Skins. Preserving Insects, and Birds' Eggs. Cases for Mounting Specimens. Tailoring;. With 180 Engravings and Diagrams. Contents. — Tailors' Requisites and Methods of Stitching. Simple Repairs and Pressing. Relining, Repocketing, and Recoliaring. How to Cut and Make Trousers. How to Cut and Make Vests. Cutting and Making Lounge and Reefer Jackets. Cutting and Making Morning and Frock Coats. Photographic Cameras and Accessories. Comprising How to Make Cameras, Dark Sliles, Shutters, and Stands. With 160 Illustrations. Contents. — Photographic Lenses and How to Test them. Modern Half-plate Cameras. Hand and Pocket Cameras. Ferrotype Cameras. Stereoscopic Cameras. Enlarging Cameras. Dark Slides. Cinematograph Management. Optical Lanterns. Comprising The Construction and Management OF Optical Lanterns and the Making of Slides. With 160 Illustrations. Contents. — Single Lanterns. Dissolving View lanterns. lUuminant for Optical Lanterns. Optical Lantern Accessories. Conducting a Limelight Lantern Exhibition. Experiments with Optical Lanterns. Painting Lantern Slides. Photographic Lantern Slides. Mechanical Lantern Slides. Cinemato- graph Management. Engraving Metals. With Numerous Illustrations. Contents. — Introduction and Terms used. Engravers' Tools and their Uses, Elementary Exercises in Engraving. Engraving Plate and Precious Metals, Engraving Monograms, Transfer Processes of Engraving Metals, Engraving Name Plates. Engraving Coffin Plates. Engraving Steel Plates. Chasing and Embossing Metals. Etching Metals. Basket Work. With 189 Illustrations, Contents. — Tools and Materials. Simple Baskets. Grocer's Square Baskets. Round Baskets, Oval Baskets, Flat Fruit Baskets, Wicker Elbow Chairs. Basket Bottle-casings. Doctors' and Chemists' Baskets. Fancy Basket Work. Sussex Trug Basket. Miscellaneous Basket Work. Index DAVID McKAY, Publisher, 1022 Market Street, Philadelphia. HANDICRAFT SERIES {continued). Bookbinding. With 125 Engravings and Diagrams. Contents. — Bookbinders' Appliances. Folding Printed Book Sheets. Beat- ing and Sewing. Rounding, Backing, and Cover Cutting. Cutting Book Edges, Covering Books. Cloth-bound Books, Pamphlets, etc. Account Books, Ledgers, etc. Coloring, Sprinkling, and Marbling Book Edges. Marbling Book Papers. Gilding Book Edges. Sprinkling and Tree Marbhng Book Covers. Lettering, Gilding, and Finishing Book Covers. Index. Bent Iron ^A/ork. including Elementary Art Metal Work. With 269 Engravings and Diagrams. Contents. — Tools and Materials. Bending and Working Strip Iron. Simple Exercises in Bent Iron. Floral Ornaments for Bent Iron Work. Candlesticks. Hall Lanterns. Screens, Grilles, etc. Table Lamps. Suspended Lamps and Flower Bowls. Photograph Frames. Newspaper Rack. Floor Lamps. Miscellaneous Examples. Index. Photography. With 70 Engravings and Diagrams. Contents. — The Camera and its Accessories. The Studio and Darkroom. Plates. Exposure. Developing and Fixing Negatives. Intensification and Reduction of Negatives. Portraiture and Picture Composition. Flashlight Photography. Retouching Negatives. Processes of Printing from Negatives. Mounting and Finishing Prints. Copying and Enlarging. Stereoscopic Photography. Ferrotype Photography. Index. Upholstery. With 162 Engravings and Diagrams. Cotttents. — -Upholsterers' Materials. Upholsterers' Tools and Appliances. Webbing, Springing, Stuffing, and Tufting. Making Seat Cushions and Squabs. Upholstering an Easy Chair. Upholstering Couches and Sofas. Upholstering Footstools, Fenderettes, etc. Miscellaneous Upholstery. Mattress Making and Repairing. Fancy Upholstery. Renovating and Repairing Upholstered Furniture. Planning and Laying Carpets and Linoleum. Index. Leather Working. With 152 Engravings and Diagrams. Contents. — Qualities and Varieties of Leather. Strap Cutting and Making. Letter Cases and Writing Pads. Hair Brush and Collar Cases. Hat Cases. Banjo and Mandoline Cases. Bags. Portmanteaux and Travelling Trunks. Knapsacks and Satchels. Leather Ornamentation. Footballs. Dyeing Leather. Miscellaneous Examples of Leather Work. Index. Harness Making. With 197 Engravings and Diagrams. Contents. — Harness Makers' Tools. Harness Makers' Materials. Simple Exercises in Stitching. Looping. Cart Harness. Cart Collars. Cart Saddles. Fore Gear and Leader Harness. Plough Harness. Bits, Spurs, Stirrups, and Harness Furniture. Van and Cab Harness. Index. Saddlery. With 99 Engravings and Diagrams. Contents. — Gentleman's Riding Saddle. Panel for Gentleman's Saddle. Ladies' Side Saddles. Children's Saddles or Pilches. Saddle Cruppers, Breast- plates, and other Accessories. Riding Bridles. Breaking-down Tackle. Head Collars. Horse Clothing. Knee-caps and Miscellaneous Articles. Repairing Harness and Saddlery. Re-lining Collars and Saddles. Riding and Driving Whips. Superior Set of Gig Harness. Index. Other Volumes in Preparation. DAVID McKAY, Publisher, 1022 Market Street, Philadelphi; WORK'' HANDBOOKS ELECTRO-PLATING ELECT RO-PLATIMI WITH NUMEROUS ENGEAVINGS AND DIAGRAMS EDITED BY PAUL N. HASLUCK EDITOR OF "work" AND "BUILDING WORLD" AUTHOR OF " HANDYBOOES FOR HANDICRAFTS," ETC. ETC. PHILADELPHIA DAVID McKAY, Publisher ()10, SOUTH WASHINGTON SQUARE 1905 'f -• \\z^ K o ") y}'^C^' 5 2^ Q PREFACE. I This Handbook contains, in a form convenient for everyday use, a comprehensive digest of the informa- tioQ on Electro-plating, scattered over more than twenty thousand columns of Work— one of the weekly journals it is my fortune to edit — and supplies concise information on the details of the subjects on which it treats. In preparing for publication in book form the mass of relevant matter contained in the volumes of Work, much had to be arranged anew. However, it may be mentioned that a number of articles by Mr. G. E. Bonney have been incorporated in the text. Readers who may desire additional information respecting special details of the matters dealt with in this Handbook, or instructions on kindred subjects, should address a question to Work, so that it may be answered in the columns of that journal. P. N. HASLUCK. La Belle Sauvage, London. Fehniary, 1905. CONTENTS, I.— Introduction : Tanks, Vat.'^, and other Ap paratus II.— Batteries, D3^namos, and Electrical Acces soriei ..... in.— Appliances for Preparing and Fini Work IV.— Silver plating v. — Copper-plating .... YL— Gold-plating VII. — Nickel-plating and Cycle-])lating VIII.— Finishing Electro-plated Goods . IX. — Electro-plating ^Yith Various Metals Alloys Index shing and 24 5G 71 90 101 125 145 154 158 LIST OF ILLUSTRATIONS. FIG. PAGE 1.— Diagram showing Positions of Anode and Catiiode in Electro-plating 11 2.— Scouring Trough 16 3— Plating Vat 17 4.— Iron Stand for Vat 19 5.— Copper Hook . . . 19 6.— Steam-heated Sawdust Pan 21 7.— Roseleur's Plating Balance 22 8.— Daniell Cell 27 9.— Bun sen Battery 27 10.— Wollaston Battery 31 11.— Part of Battery Plate Support 33 12.— Battery Plates Mounted for Use 33 13.— Smee Cell 34 14,— Battery of Smee Cells 35 15.— Fuller Cell 37 16.— Gassner Dry Cell 39 17.— Leclanche Cell 39 18.— Electro-plater's Dynamo 45 19.— Semi-enclosed Plating ' Dynamo 4? 20.— Conducting and Supporting Rod 51 21.— Resistance 53 22.— Resistance Bo^d, combined with Ammeter . . . 53 23.— Ammeter showing Rate of Deposit 55 24.— Diagram of Electrical Connections 55 25.— Treadle Polishing Machine 57 26.— Bench Polishing Machine 57 27.— Power-driven Polishing Machine 58 28, 29.— Spindles for Mops and Dollies 58 30.— Combined Treadle Scratch Brush and Polishing Lathe 59 31. 32, 33.— Leather-covered Bobs 61 34.— ^Sections of Bobs 65 35.— Emery Tape Machine 65 36.— Buff Stick 65 37.— Calico Mop 65 38.— Woollen Brush 66 8 Electro-PL A ting. i'lG. PAGE 39.— Section of Circular Brush 67 40, 41.— Scouring Brushes 67 42, 43.— Potash Brushes 68 44.— Scratch-knot 68 45, 46.— Hand Scratch-brushes 68 47.— Brass Wire Brush 69 48.— Crimped Wire Cup Brush 69 49.— Turk's Head Cup Brush 69 50.— End Brush 69 51, 52.— Watch-case Brush 69 53.— Inside Thimble Brush 69 54.— Inside Box Brush 69 55.— Inside Ring Brush 69 56.— Bottom Brush 69 57— Scratch Knot Lathe 70 58, 59, 60.— Dipping Baskets 75 61.— Small Gilding Outfit 103 62.— Improved Hook for Nickel Anode 130 63.— Straight Burnisher 149 64.— Curved Burnisher 149 65.- Curved Burnisher 149 66.— Curved Burnisher 149 67.— Round Burnisher 149 63.— Hooked Burnisher 150 69.— Curved Burnisher 150 70.— Burnisher for Corners 150 71.— Hooked Buruislier 150 72.— Pointed Burnisher 150 73.— Agate Burnisher . . .151 74.— Agate Burnisher 151 75.— Agate Burnisher 151 76.— Agate Burnisher 151 77.— Buff for Polishing Burnishers I53 BLBCTRO-PLATING. CHAPTER I. introduction: tanks, vats, and other apparatus. Electro-plating is the process by which a metal or alloy held in solution by a liquid is deposited electrically on a prepared surface. From the solu- tion, the metal (nickel, silver, brass, copper, etc.) is thrown on to the object receiving the deposit, and simultaneously an equal quantity of a similar metal to that held in solution is fretted off from metal plates (anodes) suspended in the electro- plating bath. Thus, although the solution is being constantly robbed of metal, it is yet being fed, and so its strength is maintained. Of course, the anodes must be plates of similar rhetal to that contained in solution ; thus, nickel anodes in a nickel solution, silver anodes in a silver solution, and so on. Anode is the name given by Dr. Faraday to the positive plate or wire in a solution undergoing electrolysis. It is derived from two Greek words : ana, meaning "upwards"; and odos, "a way'' — the way in whicli the sun rises — and is an indica- tion that the current rises from the battery to enter the electro-plating solution, this way being from the negative element of the battery to the positive element in the solution to be electrolysed (see the arrows in Fig. 1). The negative element of a battery receives the electric current immediately it is generated, and transmits it to the anode T o Electro-pla riNG. placed in the electro-plating bath ; the negative element is, therefore, the positive pole, and its connection to the anode by a wire makes the anode the positive pole or element in the solution. By way of illustration : the carbon element in a Bun- sen battery (see pp. 28 to 30) is the negative element, because it receives the electric current generated by the positive, or zinc, element of the battery ; but it is also the positive pole, because, through it and its metal connections, the current is transmitted to work outside the battery. Fig. 1 shows at a glance what is meant. Another scientific term has now to be referred to. Anion is a term invented by Dr. Faraday to indicate the radical of an acid, or the portion of a salt set free at the anode during electrolysis. It has been defined as " the electro-negative, or chlo- rous radical of the acid or salt decomposed." Assume that a solution of the double cyanide of silver and potassium is being used in the work of electro-plating. The salt of silver in this solution is combined with a salt of potassium, and three distinct substances are present, apart from the water which holds them all in solution ; these are —silver, potassium, and cyanogen. When the electric current is passing through the solution in the process of plating, silver and potassium are set free at the goods being plated, and cyanogen is set free at the silver anode. The salt is thus broken up or decomposed, and cyanogen is the anion of this salt. Anodes may be soluble or insoluble in an electrolyte, as may be required to suit the nature of the work in hand. Insoluble anodes are used when it is wished to decompose an electrolyte, and break it up into its several component parts without adding another element to it, as when acidulated water is decomposed by the electric current to form oxygen and hydrogen — in which case a platinum anode is used, because platinum Tanks, Vats, and other Apparatus. ii is not soluble in the acidulated solution. Insolu- ble anodes are also used when it is wished to extract all the metal from its solution, and deposit it in a pure condition on the cathode (the article plated). Anodes are said to be insoluble when they are made of elements which are neither soluble in the solution to be electrolysed, nor can be made soluble therein under the influence of the electric current. Some solutions of the acids and alkalis will act very feebly, or not at all, on an element, even when heated to boiling point, but ANOC CATHODE 1. — Diag-ram showino- Positions of Anode and Cathode in Electro-plating-, will dissolve it freely when a current of electricity is passed from it through the intractable solutions. For instance, gold is only feebly soluble in a strong solution of potassium cyanide when exposed to air, even when the solution is heated ; but it is freely soluble in the same solution when only a feeble current of electricity is passed from it through the solution. Insoluble anodes are generally made of platinum or carbon. Soluble anodes are used when it is wished to maintain an electrolyte (the plating solution) at its 1 2 Electro-pla ting, original strength— that is, to contain the same quantity of metal in the solution after it has been worked as it had when first made up. To do this, the anode must be only soluble in the solution whilst the current is passing, and then only to an extent equal to the rate of metal deposited. Un- less an equivalent of metal is dissolved from the anode for each equivalent of metal deposited at the cathode, the original composition of the solu- tion cannot be maintained during the process of electrolysis or plating. The cathode is the opposite of the anode, the term being derived from the Greek fcafa, meaning " down,'^ and odos, "a way'." Thus the word sig- nifies that the current passes down to it from the anode ; the current returns to the negative pole of the battery attached to the positive plate, thus completing the electrical circuit. The object being plated forms the cathode ; and just as the anode is connected electrically to the battery's positive pole, BO is the cathode connected to the negative pole. For the present, this is all the theory of the process of electrolysis that it is desirable to explain, further information being given as the practice of electro-plating is dwelt upon. It must not be inferred from the theoretic explanation just given that electro-plating consists merely in taking any metal article, making the necessary connections, immersing the article in the solution, and then taking it out bright with its new coat of deposited metal. There is much to be understood before successful plating can be accomplished ; the appliances necessary for work on a big scale are many and expensive ; and the manipulation of the various metals calls for a special knowledge of the characteristics of each one. This hand- book will deal with many matters of importance to the electro-plater, and will discuss, in the order in which the items are here mentioned, the electro- Tanks, Vats, and other Apparatus. 13 plater's shop, tanks, vats, and other general requisites ; batteries, dynamos, and electrical ac- cessories ; the appliances for preparing the rough metal surfaces to receive the electro-deposited coat, and for polishing the plated ware ; the proper materials, appliances, and methods em- ployed in electro-plating with silver, copper, gold, nickel, iron, lead, tin, platinum, and alloys, and the methods of finishing plated goods. Persons desiring a small plating plant for the purpose of treating trinkets, miscellaneous small articles of the nature of spoons, forks, etc., need not be deterred from carrying out their wishes by the magnitude of the operations or by the expense of the apparatus described in this and succeed- ing chapters. Metal can be polished by hand to look almost as ))right as machine-polished metal, using the same polishing materials and suitable brushes. Small quantities of the same solutions can also be used in smaller vessels, and gold, silver, etc., can be deposited in good condition with current obtained from small cells. It must be understood, however, that the same strict attention to absolute cleanliness, and care in preparation, must be observed in small operations, and the same rules must guide the worker when plating a spoon or a screw as when plating the handle-bar of a bicycle. Readers will find that special attention is paid to the requirements of the amateur and small professional plater in later chapters, their limitations having been taken into careful consideration. The plating shop must be well lighted and ventilated, and kept at a temperature of about 60° F. Good light, preferably from high windows or from a skylight, is necessary for the examina- tion of the work ; but receptacles containing silver solutions should be protected from the action of direct sunlight. Good light is required over the scouring trough and vats, to enable the workmen 14 Electro-PL ATI XG. to note changes of colour in the metals ; but the light over the vats should be a northern light if possible, because sunlight decomposes all plating solutions. The plating shop should be roomy and clean, for the most perfect cleanliness in the pro- cess is necessary to success. The plating vats should be covered with canvas when not in use, to exclude dust. Ventilation is necessary, because all the exhalations of gas from the solutions are extremely poisonous and soon debilitate the strongest work- men when fresh air is absent. Not only is an even temperature conducive to regular working of the solutions, but the employes do better and more work when the shop is well ventilated and comfort- ably warmed. If the solution vats are placed in a corner of an ordinary workshop, they will soon get con- taminated with dust and dirt. If the dynamo is near the polishing lathe, or where metal dust is flying about, it will soon be ruined. Metal castings, forgings, etc., are surfaced for plating on emery bobs, etc., as will be described in later chapters ; they are then immersed in a hot solution of caustic potash, to loosen and re- move grease and oil contracted at the polishing lathe. The solution for this purpose is contained in a wrought-iron tank, the usual dimensions for which are 4 ft. by 2 ft. by 1 ft. 9 in., to hold 50 gallons of liquid ; or one for larger work, measuring 5 ft. by 2 ft., to hold 100 gallons. The size of the tank will be determined by that of the work, and the vessel must be large enough to receive the longest articles likely to be plated. It is made of wrought iron, which is not attacked by caustic potash. Tanks of galvanised iron, lead-lined tanks, zinc tanks, and tanks with soldered joints are unsuit- able, because all these metals and solder are soluble in caustic potash, which will hold the dis- solved metal in solution and deposit it on any articles cleaned in the tank. Tanks, Vats, a.yd other Apparatus. 15 As the potash sohition will have to be worked hot, the tank must be placed in a position where ifc can be conveniently heated, either by steam passing through a coil of iron pipe in the solution, hy an ordinary furnace in which coal or coke is burnt, or by gas jets. Steam and gas are prefer- able to coal, because the heat can be regulated to a nicety, and there is no danger from fire after the day's work is done. Even when heated by steam, it is advisable to support the tank above the floor on brickwork to a height suitable for easy working. The solution is composed of American potash dissolved in water, at the strength of 1 lb. to each gallon of water. The articles are rinsed in hot water after they are taken from the potash tank, so a second tank, of equal dimensions and of the same material, must be fitted up in a similar manner next to the potash tank. This is kept supplied with clean hot water. In the preparatioii of articles to be plated, the polisher aims at getting the finest polish obtain- able on the surface of the article ; whilst the plater tries to free the surface from every trace of grease, oil, sweat, and other foreign matter. The polished work may be beautifully clean from a polisher's point of view, and yet be very dirty when viewed from the plater's point of view. The surface musi be chemically clean before the article is placed in the plating vat, to ensure the deposited coat oE metal adhering firmly to the surface of the metal on which it is deposited. The vessel in which the articles are thus further cleansed is named the scouring trough or tray, and is show^n by Fig. 2. It consists, as shown, of a shallow trough of thick wood divided into two parts, lined with lead, and furnished at one end with a plug and overflow pipe. In some scouring trays a narrow shelf is fixed a little below the upper edge, and the work rests on this whilst being cleaned. Some work- 1 6 Electro-pla ting, men hold the work on a piece of board placed across the tray. The tray must be placed on strong wooden trestles, at a height to suit the workman, and kept half full of clean water, to rinse the articles after scouring. The plating vat is the name given to the vessel intended to hold the plating solutions. This vessel must be roomy enough to take the largest article likely to be plated in it, and then leave an abundance of space all round. It is usual to plan plating vats to hold several such articles at Fig. 2. — Scouring Trough. once, so that time may be saved. Those in general use for nickel, copper, brass, and silver- plating, are made of thick pine-wood, well jointed, and strengthened with iron bolts across the ends, lined with sheet-lead put together with burnt joints, then match-lined to prevent metallic con- tact with the lead lining. The appearance of these vessels when finished is shown by Fig. 3. They are made in a great number of sizes, the capacities ranging from 19 gal. to several hundred gallons. A vat to hold the solution may be of vitreous stoneware ; but this material is liable to fracture. Tanks, Fats, and other Apparatus. A7 and is not easily made into large rectangular vessels. The next best is enamelled iron, which, being smooth, retards the creeping action of the cyanide salts, so that the sides of the vat are kept clean, and enamelled iron vats are suitable for small work ; their use is almost compulsory when the solution must be used hot. In large plating establishments the vats are wood, lined with lead, as already mentioned. Plating vats constructed of thick slate slabs, grooved and well bolted together, are also sold for the purpose, but apparently they cost 50 per Fiof. 3.— Platino- Yat. cent, more than the lead-lined wood vats. Vats made of iron only, unless they are lined with thick enamel, are altogether unsuitable as plating vats ; copper, brass, iron, and zinc are readily corroded by the action of the acid or the alkali present in the plating solution. A light vat should be supported on short stout trestles, at a height suitable to the workmen — that is, with the upper rim about the same height as an ordinary table. B Two, three, or four such I 8 El EC TR O-PLA TING, supports will be required, according to the length of the vat. If, however, the vat is large and heavy, it should be supported by a strong founda- tion of masonry, and this should be so built as to ensure free access of air to the under side, thus preventing rot in the wood. If the floor round the vat can be coated with cement or asphalt it can be easily kept clean, and it is also advisable to have w^ooden grids on the floor by the sides of the vat, on which the workmen may stand. Special iron stands for vats can be obtained (see Fig. 4) ; these are provided with means of heating the vat by gas. It is possible to make a small electro-plating bath with glass plates cemented together and en- closed in a wooden box. The cement may be either marine glue, which can be bought, or 2 parts of pitch and 1 part of gutta percha can be melted together. Pour some of the melted material into the wooden box and spread in a thin layer over the bottom with a warm iron ; while the cement i3 warm (not hot) press the bottom plate firmly into it. The sides may be treated in the same way, but before putting in the glass plates warm them gently and coat all the edges with a thin layer of the cement, so that when they are pressed together the surfaces will adhere thoroughly ; the joints will then be waterproof. Make the wood box a trifle large, allowing room for the layer of cement, or if the glass plates be forced in and nothing allowed for contraction and expansion the glass box will probably crack at the weakest part. Another suitable cement is prepared as follows : Make some good flour paste, and allow^ to get cold. Prepare a quantity of thin glue, add 10 gr. of powdered bichromate of potash to each gill of glue, bring it to a boiling temperature, and then pour it into the cold paste w^iilst stirring. Use this cement warm, and expose to strong sunlight afterwards. It will resist acids, but not hot Tanks, Vats, axd other Apparatus. 19 cyanide of potassium solutions. Still another cement is made by dissolving best isinglass in acetic acid by the aid of heat ; it is used hot. The electrical fittings of the plating vat are described in the next chapter. The articles to be plated are suspended in the plating solution from copper rods (see p. 51) by means of short lengths of wire, named slinging wires. These are made of bare copper wires, ranging in gauge from No. 8 to No. 18, the larger Fig. 4. — Iron Stand for Vat. Fig-. 5. — Copper Hook. size being employed for heavy, and the smaller sizes for light, articles. Two wires of No. 18 will hold up a cycle handle-bar ; but it is always ad- visable to have more wires or larger wires than required merely to support the articles, since these wires convey the electric current from the goods being plated ; and an insufficient wire conductor here w^ill prevent the nickel from going on as fast or as well as may be required. Small wires offer a greater resistance to the current, and should be avoided for this reason. The connection between the slinging wires and the articles to be plated is by means of copper 20 Electro-plating. hooks, the usual pattern of which is shown by Fig. 5. The plated articles are rinsed in hot water after leaving the plating vat, and are then trans- ferred at once to hot boxwood sawdust, in which they are dried quickly. This treatment is needed to prevent the coat of deposited metal from being marked by stains. The sawdust is held in a shallow pan or tank of iron placed next the hot water tank. This pan is heated by hot water or steam. If hot water is used, it occupies the double bottom, this being heated by steam jets ; by the other method, the steam passes through a coiled pipe in the double bottom (see Fig. 6). Direct heat from a fire or from gas jets is in- admissible, because this would char the sawdust, and thus stain the work. If live high-pressure steam is employed, this should be used in a coil of pipes not directly in contact with the sawdust (see Fig. 6), as such very hot steam is liable to char the sawdust. Boxwood sawdust is employed, because this does not contain resinous matter, likely to be extracted by heat, and etain the metal ; but the sawdust of sycamore could be used as a substitute if more readily obtainable. The sawdust tank and the hot-water tank may be of galvanised iron, if this is of any advantage. The Bunsen burner will frequently be useful. It is composed of a short burner inside a piece of gas barrel some five or six inches in length, to which air is admitted at the lower end. The air mixes with the incoming gas in the barrel, and the mixture burns together at the top with an intensely hot, smokeless, and non- luminous flame. When the tube of the burner is surmounted with a cap, the flame spurts out of the holes, and forms a " rose burner," the flame from which can be used for general heating purposes. - The balances or scales required by an electro- Tanks^ Fats, and other Apparatus. 21 plater will vary with the class of work on which he is engaged. For the ordinary work of weigh- ing the goods before and after plating, to deter- mine how much metal has been deposited, a pair of scales with a stout steel or brass beam will be required. For weighing gold and gilded articles a lighter pair, indicating a turn on one grain at least, should be provided ; these will also serve for weighing out the ingredients used in making up solutions. For rough assays and esti- mations a small cheap balance indicating a turn Fig-. G. —Steam-heated iSawdust Pan. of i\) grain will serve the purpose ; the cost of this, together with weights from 500 grs. down to y^Q grain, will be about £l 10s. For assays, analysis, and calibrations, a still more elaborate and delicate balance will be required, such as an Oertling assay balance fitted with agate bearings and indicating a turn with at least y^oth of a grain. Such a balance, with a full set of weights, will cost from £5 to £lO. In some plating establishments the weight of deposited metal is determined during the opera- tion of plating by means of a plating balance. This is merely a pair of large scales furnished with a scale pan at one end of the beam and a 2 2 Electro-PL A ting. metal frame suspended over the bath at the other end. The goods to be plated are slung to the metal frame, and the whole is balanced by weights placed in the scale pan. The pillar of the beam is connected to the negative pole of the machine or battery. As the metal goes on th-^ goods to 7. — Roseleur's Plating- Balance. be plated, the beam is thrown out of balance, and the exact weight deposited can be ascer- tained at any time by additional weights placed in the scale pan. Roseleur's plating balance is shown by Fig. 7. Tlie beam carries at one end a metal ring e, from which the objects to be plated are suspended in Tanks, Vats, and other Apparatus. 23 tlie bath B. The anode a is shown as a rod con- nected through terminals, etc., to the positive pole of the battery. From the opposite end of the balance the pan s is hung. A metal pin m dips into the mercury cup n, and this cup is connected to the negative pole of the battery. The path of the current is therefore from the battery by way of the anode a through the bath, and thence, by way of the articles to be plated, through the beam and mercury contact back to the battery. In the horizontal position of the beam, m does not make contact with /(. But the weight of the articles is balanced by adding weights to the pan s, and further weights are then added equal to the weight of silver to be deposited. This brings m down and completes the circuit. When the re- quired w^eight of metal has been deposited, the left arm of the beam (as seen in Fig. 15) rises and breaks the circuit. It will be seen that the balance is automatic, cutting off the current when the articles are plated to the extent intended. The work of the plating balance is done in a different way by a special ammeter (p. 54) which records the amount of silver deposited per hour. Beakers are tumblers made of very thin Bohemian glass for special use in chemical manipulations where small quantities of acids and other liquids are employed at high temperatures. Tumblers made of ordinary glass would soon break in pieces, but these thin glass beakers will bear boiling water being poured into them, or will hold acid whilst it is being boiled in them over a gas stove. They are also useful in analysis of solutions, as the clear glass enables the opera- tion of precipitation to be observed whilst the operator holds the beaker away from his face, and thus avoids breathing the deleterious fumes. 24 CHAPTER II. BATTERIES, DYNAMOS, AND ELECTRICAL ACCESSORIES. The electric current used to deposit metal from plating solutions must be obtained from a con- venient source ; this may be a battery for occa- sional jobs, and for the general use of the amateur or small professional ; and it may be a dynamo when large quantities of work have to be treated. The advantages of the dynamo are many. The current is more constant, labour is lessened, and the cost of maintenance is much reduced. The current can also be regulated, and thus any class of work can be done from one machine. A plating dynamo gives a large current at a low pressure ; the armature may be of the drum or ring pattern, and the machine is shunt wound. With a large machine, capable of giving, say, 200 amperes, large surfaces of work may be acted on in several vats simultaneously, and nickel-plating may pro- ceed at the same time as silver-plating. The electro-motive force required to be sup- plied by the battery or dynamo varies according to the bath. Thus, f<>r gold and silver, it may be from ^ to 4 volts ; for copper, with an acid bath, it may be from ^ to 1^ volts, or, with a cyanide bath, from 3 to 6 volts. The amperage will vary with the area of the anode and cathode surfaces. The word battery, as applied to electrical ap- paratus, belongs strictly to a collection of Leyden jars charged with static electricity. These dis- charge their store of force in a violent manner, totally unlike the equable flow of current obtained from collections of voltaic or galvanic cells. Batteries, Dynamos, and Accessories. 25 C* tjo J. ■J> «^ d ^1 e3 ed (D -d '?^bb 'H^bb ft ft ^ ft * >> i-i d t- d ~|J OJ .d (U -^H 0) •^ p > &i > P^ d |5i •"S ^^ :d >' ^i^' ^ ^ 11 ^1 d ^ "2 "^ "" ft-^ II -i ^ ft a 1" ^1 U^ |bO %S § ft - _d ft 2t 2" Is" 331 •s^ ft-^ 2 .'-^l -3i .5 ce d w w :^ W 0? 1— < . l-s 1 1 6 m |.i| '0 -d 9 2, i ? LO rf S'S i-H T15 5^ 01 6 6 6 6 ■^ i i w rn ^ '0 -fcj -4-> ^'=r' p "o "o !-» t> C5 9 I- t- 6 6 '~* rH "r 3 '"' ^ ^ ^ -^i '■'o _o ^ _0 F-< 'C ^ ri d rM "S t- e d d 'O lis p's d d ^' d d «^ -S .2 '^ ^ oi ^ Ol £ ^ ftX3 , ft*^:: ft"X3 S '-^ 'B^ S 4 ^r6 :§ ^:2 •d^ g -dl g s^ ~ '^ ^ ^, 'uS ^ "^ M ^; C 50 'J^J jH w CM d 'C 0" d 't^ o'' BZ'^ ^^0 .-, ^ >— 1 ._ r^ ^ .-1 TJ lis 11.2 lis lis is 2 (X, N N N N N |.| 1 * d ^ -^ d ^:2 d'^ '5 2 ■si"-! 11 - 1 d _d d . IS ll '< fi< Oh .0 "S>^ ^ • C pj -d a "oiJ © ?J s « s • S ,^4 03 d ^ ll d & a d II 2 6 Electro-pla ting. French electricians speak and write of such generators under the name of "Piles/' doubtless in deference to the form of the first voltaic generator of electricity made — the pile of metal discs invented by Yolta. English electricians apply the word battery to all apparatus in which electricity is generated by chemical decomposi- tion, and also to tAvo forms of storage cells known respectively as accumulators and Leyden jars. A tabulated list of the batteries in use by electro-platers is given on p. 25, and the table will show at a glance the battery most suitable for any particular work. Other batteries, such as the Fuller, Wollaston, Gassner, and very occasionally the Leclanche, are also used by some platers ; these will be referred to later. The Daniell is best for depositing copper from its sulphate solution and silver from the usual plating solution, but the Bunsen may be used for this purpose if the exciting liquid is sufficiently weakened. One or two large cells in series will be enough for all ordinary purposes. The Bunsen is best for depositing copper and brass from their alkaline solutions, and also for the deposition of nickel, because its electro-motive force is high, enabling the current to push through high resist- ances. It is not suitable for the work of silver- plating, gilding, and electrotyping, because its high E.M.F. causes the metal to go on too fast and in a granular condition. In all these operations the Daniell will be found to be the best because its E.M.F. is lower than that of the Bunsen, and its current equally constant in volume. The Smee, and also Walker, are eminently useful cells for giving a current suitable to the w^ork of electro- gilding small articles of jewellery. Batteries with a high E.M.F. cause gold to go on too fast, and give the deposit a brown colour. Batteries^ Dynamos, and Accessories. 27 Some information as to the form and construc- tion of the various batteries used by electro- platers may now be given. The Daniell cell is known in several modifica- tions, Fig. 8 showing the internal arrangement of the porous pot form. The glass or glazed vitrified stoneware jar J contains the cylindrical plate c (made of sheet copper), the porous pot p (made of uri glazed earthenware), and the zinc Bunsen Battery. rod z. Inside the porous pot dilute sulphuric acid is poured, while the copper plate c stands in a saturated solution of copper sulphate. The connections are made to the two wires shown in the illustration. The maximum electromotive force of the cell is about 1-14 volts, with an internal resistance of 3 ohms in the 3-pint size, and 1'6 ohms in the 3-quart size. A Daniell battery is re-charged in the following way: Thoroughly clean all the parts and reamal- 2 8 Electro-pla ting. gamate the zincs ; charge the porous pot, contain- ing the zinc, with a solution of 1 part of sulphuric acid in 12 or 13 parts of water, and the outer jar, containing the copper plate, with a saturated solution of sulphate of copper. The small sieve or tray near the top of the containing jar, but below the level of the copper solution, should contain crystals of sulphate of copper to keep the solution saturated. If copper is allowed to de- posit on the porous pot, the current will fail, not only on account of a higher internal resistance, but also because this short-circuits the cells. To prevent this, the zinc and also the zinc sediment must be kept from touching the porous partitions. The Daniell battery is very constant. Whilst the sulphate of copper solution is kept saturated, and the zinc kept in working order (well amalga- mated — coated with mercury), the current will not flag at all during the day ; it is therefore most suitable for silver-plating and gilding, but it is very troublesome to keep in working order, unless kept well at work and employed every day. The Bunsen battery as used in England is made up of an outer containing cell of stoneware, containing a cylinder of amalgamated zinc, inside which is a cell of porous earthenware containing a square bar of carbon (see Fig. 9). The outer cell is charged with sulphuric acid diluted with water, and the inner cell is charged with strong commercial nitric acid. The electro-motive force given by this cell is variously stated by authorities as r85 to 1"95 volts. The internal resistance of the cells varies with their size, the condition of the porous cell, and the condition of the acid charges ; the resistance being variously given as 0-30, 0-08, and 0*06 ohms These probably repre- sent respectively the pint, quart, and half-gallon sizes of cells used by the persons testing them. The E.M.F. of the quart Bunsen when charged with sulphuric acid diluted with twelve parts of Batteries, Dynamos^ and Accessories, 29 water in the outer cell, and strong nitric acid in the inner cell, may be put down at 1*86 volts, and its internal resistance at 0*08 ohm. This will give a current of about 23 amperes on a short circuit, or 1"78 amperes through an external resistance of 1 ohm. As gold is deposited from its solutions at the rate of 37"31 grains per ampere hour, this current will deposit 64' 17 grains per hour. It will also deposit 1()550 grains of silver in the same time. As, however, silver is best deposited with a low E.M.F. of from 1"5 to 1*6 volts, and gold with an e.m.f. of r2 volts, the Bunsen has a ten- dency to deposit both of these metals in a rough condition, unsuited to work that must be bur- nished. The Bunsen cell is w^ell suited to gilding and silvering small articles, such as chains and trin- kets slung to fine wires offering a high resistance ; but, for plating spoons and forks, and for plating on large surfaces, the current from a large Daniell, Smee, or Wollaston is preferable, because it deposits a coat more adapted to the action of the burnisher. The Bunsen cell, however, has become a favourite with trinket platers, because it is easy to set up and cleanly in working, thus causing very little labour in setting up and putting away. A Bunsen battery may be made as follows : Obtain a stoneware jar of quart size or larger, and in it place a cylinder of zinc about -| in. thick ; inside this zinc cylinder place a porous pot about \ in. smaller in diameter but 2 in. higher than the stone cell, and inside the porous pot put a rectangular stick of carbon, say 2 in. by \\ in. by 10 in. to 12 in. long. The zinc cylinder must be well amalgamated with mercury, being dipped in a dilute solution of oil of vitriol to clean, and then placed in a shallow porcelain tray (such as photographers use) in which is a quantity of hydrochloric acid and mercury. On rubbing the 30 Electro-plating. mercury over it the zinc will be coated inside and out. Allow the zincs to stand on end for a time to drain the excess mercury off. Fix the zincs and carbons w4th brass connections, and join the batteries in series — that is, connect the zinc of one cell to the carbon of the next, leaving a free end of the zinc and of the carbon. The batteries must be charged with acid as follows. Run the nitric acid inside the porous cell till about three-quarters full, and fill the space between the porous cell and the stoneware with a mixture of 1 part of sulphuric acid to 9 parts of water. The French Bunsen is made up with sulphuric acid in the porous cell with the carbon, tlius pro- ducing a constant generator with a lower e.m.f. The current from the French Bunsen has an e.m.f. of 1"8 volts at starting, but it soon falls to 1'6 or 1"5 volts when the circuit is closed, because the sulphuric acid is inferior to nitric acid as a de- polariser. This form is also less troublesome to keep in working order than the ordinary Bunsen, and it is free from noxious fumes, which render the presence of the ordinary Bunsen well-nigh in- tolerable in close workshops. Nearly all the batteries given in the list on p. 25 may be modified. A modification of the Bunsen has just been noticed. In the table, mention is made of the various strengths of acid solutions to be used in the zinc compartments of the batteries. These suggest other important modifications, the e.m.f. of the battery varying with the quantity of acid used. For instance, the E.M.F. of the Bunsen charged with a solution of one part sulphuric acid and eight parts of water may give an e.m.f. of 1-95 volts, but when charged with a solution of 1 part sulphuric acid to 10 or 12 parts of water the e.m.f. may fall to even less than 1-80 volts. The Daniell, Smee, and Walker may be modified in like manner. The Wollaston battery takes the form shown Batteries, Dynamos, and Accessories. 31 by Fig. 10. All the couples of copper and zinc plates are contained in separate cells a d of glass or porcelain, which hold the sulphuric acid or other exciting fluid. The zinc plates are each kept adjusted centrally by wooden slips between the halves of a doubled copper plate bent round under them. The whole set of plates is connected by copper strips m, and is secured to the wooden frame K ; so it can at pleasure be lifted out of the fluid and the action of the battery stopped. Fio-. 10.— AVollaston Battery. This is one of the earliest galvanic batteries intro- duced after Volta's original invention. The Wollaston battery is the least costly and least troublesome of all the plater's galvanic bat- teries, but it is also most inconstant, as its cur- rent is apt to fall off rapidly after being set to work ; but it recovers its strength after a few minutes' rest, and it is a handy battery for such short jobs as generally fall to the lot of the country jeweller. One form of it may be made at home as follows: Get three or four open-mouthed jars of glass, stoneware, or porcelain, of any size 32 ELECTRO'PLATIXG, from one quart to one gallon, the larger size being preferable ; these are to serve as battery cells. Next get some three or four plates of rolled zinc, just large enough and long enough to go in the jars ; clean the plates well in hot water contain- ing washing soda, and rinse them in clean water. Pour some water in an earthenware baking-dish, about enough to cover a zinc plate ; then pour in carefully some sulphuric acid, 1 part for every 10 parts of water in the dish. In this mixture immerse the zinc plates, one at a time, and pour on each a small quantity of mercury ; spread this over both sides of each plate with a mop made of tow containing a few brass wires, and then coat them perfectly. This is termed " amalgama- ting" the zincs. The acid mixture may be used with some more to work the battery, and the excess mercury can be used over again. These zinc plates have to be suspended to a cross-head of wood (each plate between two plates of copper in each cell). The wood supports should be cut out of hard wood to the shape shown in Fig. 11, so as to enclose each zinc plate between two pieces of wood, the plates fitting in the recesses cut for them. The wood should now be well varnished, or, better still, well soaked in melted paraffin wax. Each zinc plate can then be enclosed between two wooden supports, these secured to each other by long brass screws passing through both, and the plate held up by a binding screw on the top, as shown in Fig. 12. A pair of copper plates must now be obtained for each zinc plate, the copper being slightly larger than the zinc, and of any thickness. They work all the better if they are cross-scored with a file, or if they have a rough coat of electrotype copper de- posited on them ; they work better still if they are coated with platinum, but this necessitates the use of a battery and a costly platinum solu- tion. The copper plates may be secured to the Batteries^ Dynamos, and Accessories. 33 cross-heads on each side of the zincs by very short brass screws, care being taken not to let any of them touch the zinc plates ; or they may be clamped with brass clamps (Fig. 12) sold for Fi^ 11.— Part of Battery Plate Support. I for Use. tlie purpose. When clamps are used, it is always quite easy to remove the plates for cleaning, and to reverse the zinc plates so as to wear both ends equally. The battery jars are charged with an acid mixture, made by pouring one part by volume 34 r.LECTRO-PLA TIXG. of sulphuric acid into twelve parts of water, and allowing it to cool before using. The plates are suspended by the wooden cross-heads in this mix- ture. When it is wished to increase the pushing- force (the E.M.F.) of the current, the copper plates of one cell are connected by a length of No. IG copper wire to the zinc plate of the next cell, and so on through tJie whole series of cells, taking in as many as may be wanted. When a low- tension current of large volume is desired, all the copper plates of the cells are connected together by one set of wires, and all the zinc plates by another set of wires. The cells may be placed in a wooden tray or in a shallow box, and all the cross-heads may be secured to a long bar of wood, w^iich may be suspended to a suppoi't above, or to an arrange- ment for lifting all the plates out of the cells when the battery is not wanted. This arrangement will also be found to be most convenient for con- trolling the current, as its volume can be lessened at any time by exposing a less surface of the plates to the action of the battery acid. When the battery is not re- quired for use, the plates should be lifted out of the cells, and if they are not likely to be wanted for a few days, they should be well rinsed in an abundance of water, to free them from acid. It will be necessary to take out the zinc plates occa- sionally, clean them, and freshly amalgamate their surfaces. This must be done at any time if the .^mea Batteries, Dynamos, and Accessories. 35 plates give off a liissing noise, and appear to be blackened by the acid. The Smee cell is constructed on the principle shown in Fig. 13. In a rectangular glass vessel are two zinc plates Zn, held together by a screw, and between them, well insulated, is a platiuuui l^late or a silver plate covered with platinum (see Ag.). The vessel is filled with diluted H.2SO4, and is made larger than the plates so that the Battery of Smee Cells zinc sulphate which is forming may not come into contact with the plates, and may fall to the bottom of the vessel. A battery of Smee cells is shown bj^ Fig. 14. In this figure, z and p respec- tively indicate the zinc and platinum and their connections. It is possible to make up the Smee in a similar manner to that described for the Wollas- ton, except that platinised silver foil, soldered to copper frames, is used instead of copper plates for the negative elements, but in all other respects the battery may be made like the Wollaston, and 36 Electro-plating. will give similar results, but its action is longer sustained after being connected to the work, be- cause it does not polarise so soon. The proper exciting liquid is a mixture of one part by mea; are of sulphuric acid and seven of water, which will be found strong enough for all purposes. Fre- quently it is advisable to use only one part of acid to ten or sixteen parts of water, and to add acid as required, taking care, however, that the quantity of acid never exceeds one-fourth of the original water, for any excess above that quantity will be useless, as the liquid will then become saturated with the sulphate of zinc. Still further modifications may be made in the battery by en- larging or diminishing the size of the negative or the positive element, or both of these, and in altering the size of cell containing them. As a rule, the enlargement of elements and cells tends to an increased output of current, because the internal resistance of the battery is lowered, and there is, consequently, more available force for the outer circuit. Enlarging the negative element will frequently bring about the desired result of lowering the internal resistance of the battery and increasing its volume of current. This is specially noticed in the Daniell, Smee, and Walker batteries. The Fuller cell (Fig. 15) has an outside stone- ware jar with an inner porous pot, the outer jar having a plate of carbon in chromic acid or bi- chromate of potash solution, with one-quarter of its bulk of sulphuric acid. In the illustration a part of the porous pot is cut away the better to show the zinc. The inner porous pot contains a rod of zinc ending in a plug z, the bottom of the pot is covered with mercurj^, the remainder of the cell being filled with sulphuric acid and water. The electromotive force is 1-50 volts. One of two charges can be used for a Fuller cell. In one the porous pot with the zinc plug is Batteries, Dynamos, axd Accessories. 37 charged with a solution of 1 oz. of common salt to 1 pint of water. In the other a solution of 12 parts of water to 1 part of sulphuric acid is used. In using either of these solutions, about 1 oz. of mercury should be placed at the bottom of the porous pot, to ensure constant amalgama- tion of the zinc, thereby preventing waste. The outer jar, containing the carbon plate, is charged with a solution made by dissolving bichromate of potash 3 oz. to every pint of warm water, and then adding 3 oz. of sulphuric acid gradually, stirring with a stick. The addition of the acid causes the solution to become scalding hot, so care should be taken to make the mixture in a vessel that will not crack. All the solutions should be quite cold when the cell is put up for use. The size of the porous pot depends on the shape and size of the outer one. It should stand up about 1 in. above the outer pot, and should com- fortably hold the zinc plug without occupying too much room in the outer jar. When a battery is wanted for use for only a few minutes at a time, or merely to flash on a thin coat of silver to hide defects or discoloured patches, the Gassner dry battery may be used. This battery needs no attention in the way of setting up or cleaning, as it is always ready for work, and will furnish current sufficient to gild a brooch, scarf pin, or even a bracelet, or to plate such an article with a thin coat of silver. The large double-carbon square cells should be se- lected for this purpose, and the battery should be made up of two of these cells in series. They will last about two years, without renewal, on such 15.— Fuller Cell. 38 El EC TR 0-PL A TING, intermittent work as has just been mentioned. If used for jobs which will necessitate a constant supply of current for more than ten minutes, the battery will soon be exhausted. The Gassner cell (Fig. 16), one of the earliest of dry batteries, is complete in itself, instead of being a composite cell made up of inner and outer vessels. There is no porous cell of any kind, or any outer cell of glass, porcelain, or other break- able material. The battery case is of thin sheet zinc, Avhich may be made in any form and of any size required. The sheet zinc case, which forms the positive element, is nearly filled with a paste composed of zinc oxide and gypsum, moistened with a solution of zinc chloride. A capped cube of carbon, bearing a binding screw on its head, forms the negative element in the centre of the case, where it is surrounded by the conducting and exciting paste. The whole is sealed over with a composition resembling marine glue. It will thus be seen that there is no liquid to spill, nor is any required, as the paste is moist enough to excite the zinc, and it will retain its moist con- dition for any length of time. The cells may therefore be laid on their sides, or turned upside down, without impairing their working qualities. They may be placed in any convenient position, regardless of the temperature of the room in which they are located. When a Gassner cell is exhausted, a strong current of electricity (such as that from a battery of Bunsen cells) is sent through the cell from carbon to zinc for about an hour to regenerate its contents, but the effect is • ' t • ' ' '■'1 \ li ii: 1 1 M illi: i\t It :;!i ,:jj 1 Fig. 22. — Resistance Board, combined with Ammetei'. lever rests on the last brass piece, all the resist- ances are thrown in. Thus the plater is enabled to silver a small article safely, even w^ith current from a very large dynamo. The switch is equiva- lent to a tap in a water-pipe, each wire taken in 54 Electro-pla ting. by it acting like the plug of a tap in narrowing the hole through which the water flow^s. A resist- ance board must be placed to each vat to control the flow of current through it as required by the plater, and when an ammeter is combined with the board (as shown in Fig. 22), the current passing at any time can be seen at a glance. The ammeter (Fig. 23) measures the current, and is often fixed to the resistance board for ready reference (see Fig. 22). As the rate at which the silver is deposited depends on the current through the vat, and as the character of the deposit is greatly influenced by the rate of deposit, this instrument is of great importance, for by it the plater can determine how mAicli silver is being deposited. The dial of an ordinary ammeter show^s the current in amperes, 1 ampere being that current which will deposit 52 gr. of silver in one hour on 1 sq. ft. of suitable surface, in a fit condition for polishing. Thus, in the special in- strument made by T. Morris and Co., Birming- ham, and illustrated by Fig. 23, the lower scale shows also the w^eight of silver deposited per hour. The voltmeter is similar in external appear- ance to the ammeter, but the readings on its dial are in volts. From its readings the plater can adjust the brushes of a dynamo and regulate its speed so as to get the right voltage. Experience has proved that the silver in a silver-plating solu- tion may be separated from its salt and deposited in a good condition at as low a pressure as 2 volts ; but this may be increased to 3 or even 4 volts without altering the condition of the deposit very m.uch. However, when the pressure exceeds 4 volts, there is a tendency to a loose .and powdery deposit, which gets more pronounced as the pres- sure is increased. A voltmeter is therefore useful, but, its coils being w^ound Avith fine w^ire of high resistance, it must be placed in a shunt bridging the two main lines, and furnished with a switch Batteries^ Dynamos^ and Accessories. 55 to cut the voltmeter out of circuit after the dynamo has been adjusted to the required pressure (see Fig. 24). Fig. 24.— Diagram of Electrical ^i^^^e Connections. Fig'. 23. — Ammeter showing Rate of Deposit. The diagram of electrical connections presented by Fig. 24 should be carefully studied. 56 CHAPTER III. APPLIANCES FOR PREPARING AND FINISHING WORK. Chief among the appliances used in preparing rnetal for plating is the polishing lathe. In order to "produce a polish on the work, the first process is by file, scraper, or some similar tool, to remove the rough surface the metal has received in forg- ing or casting ; and, to do the work quickly, the instrument taking the place of the scraper or file must move at considerable speed, and the article must be held against it. The same method is required with the further processes of polishing. Figs. 25 to 27 show three kinds of machines suit- able for this work. Fig. 27 illustrates the machine more generally used where steam power can be applied. The cast-iron standard is firmly bolted to a block of wood or stone, and has adjustable bearings at the top for a circular spindle to revolve in ; each bearing has a lubricator in the centre to supply the spindle with oil. The spindle has fast and loose pulleys in the centre, and at the ends devices to hold the emery-wheel, grindstone, buff, or dolly, as may be required. The ends of the spindle should be threaded with a coarse taper screw which enters a hole in the boss of the brush or bob, and holds it firm whilst revolving. Large lathes are furnished with flanged plates at one end (see Fig. 27) in addition to the taper screws. These plates support calico mops, and grip the sides of emery wheels. Polishing lathes must be firmly bolted down on benches not liable to great vibration, and run at a speed of 1,400 revolutions a minute in polishing Appliances for Preparing Work. 57 silver. For polishing steel or other hard metals they may be run at a higher speed, up to 2,500 revolutions per minute. The brushes used witli Fig. 25.— Treadle Polishing Machine. Fig. 2G.— Bench Polishing Machine. these lathes differ in size and material according to the work required from them. A simple machine that may be fixed to an ordinary bench and worked by foot is illustrated 58 Electro-pla ting. by Fig. 26. A treadle device is fixed to the floor and carried by a standard having a plate to secure it to the bench and an upper pillar to take the wheel, buff, or dolly. This is the most simple construction that can be adopted for the work. The wearing portions are few in number, and can ^(tt|Huituu?m.JJu(»umvtim:>jM tint the copper. The process is a delicate one. A thick deposit of gold is obtained in the fol- lowing manner: The articles are frequently taken from the gilding bath and scratch-brushed to re- move the brownish appearance, then rinsed and returned to the bath. If this is not done the gold will not adhere, but will simply surround th^e article in the form of brown mud, and this con- dition is soon observed when the solution is poor, and when the current is too strong. Highly polished small steel articles, free from grease and oil, may be gilded in an electro-gilding solution of gold cyanide. When a quantity of 1 1 8 Electro-pla tixg. such articles is to be gilded, they may be done in dozens at a time if suspended in the solution in a basket of platinum gauze ; this basket must be shaken whilst the gilding process is going on. Any gold deposited on the platinum may be after- wards dissolved off in the gilding solution without doing it any injury. The steel articles are scratch- brushed and polished in the usual manner. Articles made of aluminium cannot be gilded direct in a solution of the double cyanide of gold and potassium, because the alkali therein attacks and rapidly dissolves the aluminium. They should therefore be first coated with copper in a solu- tion of copper sulphate, and then transferred to the gilding bath. The insides of mugs, spoons, salt cellars, etc., are gilded by means of a special arrangement in which the articles are connected to the cathode system ; then they are filled with gilding solution, and gold is deposited from a gold anode held in the solution by hand. If the vessel will hold any gold solution, fill it and connect it with the nega- tive pole of the battery or dynamo, and for an anode use a strip of gold on the end of a wire con- nected to the positive pole. The anode is held in the gilding solution contained in the vessel, or moved about in it as required. If the vessel will not hold liquid, it may be gilded with a rag mop wrapped around the anode and repeatedly dipped in the gilding solution, connection being made with the battery as before. The scratch-brushes used in brushing gilded work are made with very fine brass wire, some being crimped for extra elasticity combined with softness. Special shapes are required for such goods as rings and watch cases, so that the in- sides may be brushed and polished. Sometimes a good brushing with a scratch-brush is all the finish required for the insides of goods. When chains are heavily gilt, each link must be twisted Gold- PL A ting. i i 9 around and brushed, whilst only a short length of chain is held between the fingers and thumbs of both hands. Gilt articles are polished on soft mops made of swansdown, soft felt, and chamois leather, using finest rouge composition as the polishing material. The insides of rings are polished on felt fingers so tapered as to fit any size of ring. Chains are polished on broad-shaped bobs covered with soft leather on the convex sides. Thimbles and similar hollow ware have specially formed bobs made with wooden stocks of the required shape covered with fine soft felt. Contrasts in the various grades of finish are sometimes resorted to for effect. A frosted ap- pearance is secured by using a coarse scratch- brush having long bunches sparsely set in the boss, and holding a stick to the revolving brush just before it strikes the gilded articles. Raised parts are burnished with suitable burnishers made of steel, bloodstone, and agate. A final yellow blush is often imparted by a momentary dip in a new gilding solution, after which the article is rinsed in hot water and dried. Gold is deposited rapidly from ordinary electro- gilding solutions, and a sujQ&ciently strong coat may be deposited in the course of a few minutes, the rate being about 37 gr. an hour per ampere. Weigh the articles after they have been cleaned and after they have been gilded to ascer- tain the quantity of gold on them. When, there- fore, by calculation of time and current, it has been estimated that enough gold is deposited, the article must be rinsed in clean water, scratch- brushed to remove the brown appearance, dried by rubbing in sawdust or otherwise, and then weighed. If there is not enough gold on the article, return it to the gilding bath. Professionally, the weight of gold and silver deposited is according to the charge to be made 120 Electro-PL A T/XG. for the job. The article should therefore be weighed in a balance when it has been dry-finished for plating, and the weight entered in a book. If it is a ring, for instance, weighing 50 gr., and the price will allow of 2 gr. of gold being put on, it is immersed in the gilding solution for a few minutes, then rinsed, scratch-brushed, and dried, and again weighed. If it weighs 51 gr., it must be again put into the gilding solution for a few minutes, and the foregoing process repeated until it weighs 52 gr. The price per grain is easily ascertained by dividing the price of pure gold per ounce by 480, the number of grains in an ounce. Silver is reckoned by the pennyweight, taking ^ dwt. as the lowest fraction. To the cost of metal must be added the cost of labour in pre- paring and finishing, and a small addition to cover the cost of deposition. This gives the prime cost. In gilding lockets, light brooches, and similar light trinkets, the solution will get inside and re- main there during the process of scratch-brushing. This must be taken into consideration when weigh- ing the goods, and care must be taken to have them dry. Some of the hollow ware is filled with a waxy composition which oozes out in the course of gilding, and this falsifies the calculations made to determine the deposit of gold. The anuitcur and small professional plater are interested more in the gilding of such trinkets as brooches, chains, coins, rings, etc., than in larger and more ambitious work ; so it is proposed here to treat this branch of the gilder's art in greater detail. A brass ring could be taken from a man's finger, and, seeing that it is bright and clean, a person might conclude it would not need cleaning before hanging it in the gilding bath. Assume it to be merely wiped with a scrap of rag, a bit of copper wire tied to it, and hung in the gilding bath. In a few moments it receives a coat of gold all over, and nij^y be rinsed in warm water to free GOLD-PLA TING. 121 it from the cyanide salts, wiped dry with a rag, and handed back to the owner, gilded. The ring looks fairly well, but by rubbing it with the palm of the hand the very thin coat of gold can be removed in a few moments, leaving the brass bare. All trinkets may be thinly gilt in a similar manner, and the thin coat of gold can be as easily rubbed off. If the ring is left in the gold bath for a few minutes, it will take on a brown coat instead of a golden tint. This brown coat is merely the matt appearance assumed by electro-deposited gold, and this will entirely disappear on brushing the coat with a brush of fine brass wire kept lubri- cated with stale beer. But on brushing in this way an imperfectly cleaned ring as it comes from a person's finger, the ring assumes a brassy ap- pearance, because the gold w^ent on loosely over the sweaty parts of the ring, and these loose par- ticles of gold are readily detached from the im- perfectly cleaned spots by the wire brush, and this non-adherence of electro-deposited coats be- comes more apparent with thick coats than with thin ones. To get a perfectly adherent coat of electro-deposited metal, the article must be thoroughly cleaned. Let it appear to be ever so clean to the eye, it must have contracted a trace of animal grease, or sweat, if it has been handled or worn, and this film of animal matter must bo taken off in a solution of strong alkali, such as soda, potash, or ammonia, before a coat of ad- herent metal can be deposited on the article. A strong solution of washing soda may be used if nothing better can be obtained. Pearlash is a better cleanser ; American pearlash, or potash, is still stronger ; and the best cleansers (in general use by professional platers) are commercial caustic soda and caustic potash. A piece of either of these, about the size of a walnut, dissolved in half a pint of hot water, will be enough to clean a dozen or two of small trinkets or chains. First 12 2 ElECTRO-PLA ting. dissolve the potash or soda in liot water, then string a few trinkets on about 6 in. of No. 20 or Xo. 22 copper wire, and swill the bunch for a few minutes in the hot liquor. Transfer from the hot caustic solution to some clean warm water, and well rinse the trinkets in this to clear off the loosened grease. When the caustic liquid is cool, put it in a closely stoppered bottle to exclude the air, and thus preserve it for future use. After the grease has been loosened, if there is no corrosion on the article, it must be briskly brushed with a little whiting, or prepared chalk, or finely pow- dered pumice, again rinsed, and then hung in the gilding solution. If the trinkets are corroded, the corrosion must be removed in a pickle made of two parts sulphuric acid, two parts water, and one part nitric acid, after which the articles must be rinsed in clean water. Chains of a strong pattern may be rolled up in a mass between the two hands with a little whiting, and rubbed until polished ; but those of more delicate construction may not be treated in this way, but must be carefully brushed. Filigree work will require very careful treatment in clean- ing, and the gold should be deposited on it with low battery power, to prevent browning the de- posit, since it cannot be well brushed bright after- wards. Long chains of a delicate pattern should be threaded on a long thin copper wire passed through the links at intervals of from 2 in. to 3 in., or the wire should be wound spirally around the chain, to assist in conducting the current to all parts equally. Ear-rings and brooch pendants made of metal beads strung on silk should be suspended in a small basket of platinum gauze, in order that the beads may be placed in connection with a conduc- tor of electricity, since silk will not conduct the electric current. Such goods should not be put Gold-PL A ting. i 2 3 in the caustic solution, as this will dissolve silk, and cause the beads to drop off. All trinkets containing hair, photos, and other material likely to be injured by the hot gilding solution, must not be put in the caustic solution until the hair, photo, etc., has been removed. It is also ad- visable to remove glass and stones liable to injury from this cause, and to re-set them when the work is finished. Trinkets made of aluminium only will not receive a coat of gold, but will dissolve in caustic solution and in the gilding solution (see p. 118). The brush used in brushing articles before gilding may be an old, but clean, tooth-brush, or any clean brush with stiff bristles. Special care must be taken with common jewel- lery. Bits of coloured glass, called " stones, ^^ are inserted in cheap brooches, rings, etc., under the names of rubies, diamonds, pearls, etc. In the commonest goods these stones are merely attached with gum or some soluble cement, which is dis- solved in the solution, and thus the stones come off. An examination of the goods before gilding will soon detect these, and, if the '' stones '^ are not held firmly in claws, they should be taken out by steeping the articles in hot water before they are prepared for gilding. They must be re-set after the goods are gilded. Whilst preparing the trinkets, the condition of their surface must be noted. If this is scratched, dented, bruised, or pitted with corrosion, the marks cannot be obliterated h^^ polishing and bur- nishing after gilding. All such blemishes must be removed before the articles are cleaned, if they are to be removed at all, and this can only be done by hand, either by pressing out the dents with suitable pieces of wood, or removing the scratches with a fine file and burnishing the filed spot. All repairs must be done first, as it will be difficult to repair electro-gilt goods when finished. 124 'El EC TRO-PL A TING. Joints made with soft solder are difficult to coat with gold, but small joints may be doctored up by rubbing over them a wet piece of bluestone (sulphate of copper) and then touching the place with a piece of bright iron or steel. Both the iron and the joint will take on a coat of copper and cover the solder. Einse the joint in clean water, and hang the article in the gilding solution. If there are several soldered joints or much soft solder about the trinket, or if it is desired to coat a pewter medal, lead casting, zinc ornament, piece of tinned iron, or article composed wholly or partly of iron, tin, lead, or zinc, it is advisable first to coat it with copper in an alkaline coppering solution, made up as described on p. 76. At least three battery cells will be needed to deposit copper from this solution, and perhaps four cells, arranged in series, may be required to force the copper on a soldered joint ; but the copper thus deposited will be firm and adherent, and may be well polished. Use a piece of good copper, such as electrotype copper, as an anode. A mere film of copper is all that is required to protect the .irticle from the action of the gilding solution. If the film does not go on evenly in a few minutes, take the article out of the bath, briskly brusli it with a brass wire brush, and return it to tlie coppering solution. TJiis solution may be worked cold or hot, as may be desired ; but the deposit is brighter from a hot solution than from a cold one. This solution is also useful to give an 18-carat gold appearance to gilded or pure gold goods. This is done by merely flashing a film of copper over the surface when finished, then flashing a film of gold on this, rinsing at once in hot water, and drying off in clean sawdust. By careful working in this way, a clever workman can get any desired tint of gold on the surface. 125 CHAPTER VII. NICKEL-PLATING AND CYCLE-PLATING. To facilitate tlie reader's mastery of the informa- tion about to be presented, it may be said that this chapter conforms to the following arrange- ^ment: The nickel-plater's and cycle-plater's plant ; the necessary solutions ; the preparation of the work ; the preliminary coppering of cycle parts ; the actual process of nickel-plating ; the finishing of nickel-plated work ; re-plating ; the working of nickel-plating solutions in general ; and special applications of nickel-plating. In tlie cycle trade large firms have a plating sliop as a branch of their business ; but small repairers are content to send their work to pro- fessional platers, thougli, as business increases, they naturally wish to do all the work on their own premises, and so save time and intermediate profits. To this end they seek to do the plating at home, and they look about them for the in- formation necessary to guide them in laying dow^n a plating plant. This chapter is intended as an aid to tradesmen desirous of expanding their busi- ness in this way, but the information given will be of value to all who are interested in electro- plating. The cycle maker's nickel and copper plating outfit, supplied by Messrs. J. E. Hartley & Son of Birmingham, at £44, includes the following ap- pliances and materials: — Shunt-wound dynamo (4^ volts, 40 amperes, 3^ in. pulley, speed, 1,700 revolutions per minute). 12 6 Electro-pla tixg. Resistance board for regulating current. Plating vat (6 ft. by 2 ft. by 1 ft. 6 in.), lead-lined, burnt joints, bolted and match- boarded. Salts for making 100 gal, of nickel solution. Twelve nickel anodes (total weight 31 lb.) and hooks. Cable, three rods, five connections, and copper wire. Wrought-iron, potash, and hot-water tanks — the latter galvanised. Galvanised wrought-iron sawdust pan. Lead-lined scouring trough and twelve assorted scouring brushes. 28 lb. of potash, bag of boxwood sawdust, and 28 lb. of pumice powder. A dynamo of 5 volts and 80 amperes, the pulley diameter being 3^ in. and the speed 1,100 revolu- tions per minute, is supplied in the place of the dynamo mentioned above at an extra cost of £6. To the above plant must be added the following items, costing £ll, if coppering is to be under- taken : — Resistance board. Vat, 4ft. by 2 ft. by 1 ft. 6 in. Chemicals for making 50 gal. of copper solution. Four copper anodes and hooks. Three rods and connections. Twaddell hydrometer. Five pounds of cyanide of potassium. The output of such a plant (with the larger dynamo) if under the control of an efficient plater is estimated at 100 sets of cycle fittings per w^eek. A nickel-plating outfit suitable for repairers, etc., is priced at £36; it has an output of 40 sets of cycle fittings per week, and differs from the £44 nickeling plant already specified in having a vat measuring 4 ft. by 2 ft. by 1 ft. 6 in., eight anodes, and smaller quantities of chemicals and Nickel-plating and Cycle-plating. 127 materials, no coppering appliances and materials being included. Similar outfits are supplied by other makers, whose lists should be obtained. The above will be found sufficient for those who have facilities for preparing and polishing the cycle fittings, })ut if unprovided with a good pol- ishing lathe and its accessories, the cost of this must be added, since nothing can be well done without it. If a battery of large Bunsen cells is employed instead of a small dynamo, the total cost will be a few pounds less ; but a battery is not advised if power can be obtained for driving the dynamos. Batteries are messy, and the daily work of keep- ing them in order is something considerable, whilst the cost of their maintenance is a very serious item. To compete with professional platers, it is necessary to have polishing lathes driven by steam, water, gas, or some similar power, and the same source of power can be used for driving the dynamos. Directions are sometimes given for making nickel-plating solution by dissolving grain nickel in acid. As these home-made salts are inferior to those obtainable from a good dealer in nickel- plating outfits, and the quality of a nickel deposit largely depends on the purity of the salts used in making the solution, intending platers are advised to purchase the salt direct, instead of attempt- ing to make it in the workshop. The salt of nickel in general use for making nickel-plating solutions is the double sulphate of nickel and ammonia. This is a beautiful clear sea-green salt when pure, and takes the form of crystals, ranging in size from that of peas to that of chestnuts. The salt is merely dissolved in boiling water in the proportion of 1 lb. to each gal- lon, and poured into the vat when cool. Fairly good solutions may be made with 12 oz. of nickel 128 Electro-plating. salt to the gallon ; but weak solutions offer a high resistance to the current, and the deposit is liable to be powdery and loose. Rainwater is preferable to spring-water in making the solution, and it is advisable to pass it through a calico filter into the vat, to remove any loose dirt acci- dentally acquired by the nickel salt. If best nickel salt is used, it will not be necessary to add either ammonia or table salt, these being em- ployed to correct some fault in old and poor solutions. If for some special reason it is desired to make the. double salt of nickel and ammonia at home, proceed as follows: Take of nickel 14 oz., dis- solve it in a mixture of three parts of strong nitric acid, one part of strong sulphuric acid, and four parts water. When dissolved, which is in- dicated by the fumes (caused by chemical action) ceasing, add a little liot water and filter ; the deep green liquid obtained is a strong solution of nickel sulphate. Then make up a strong solution of ammonium sulphate l)y dissolving 4 lb. of the salt in a gallon of water. For preparing the plating solution mix about half of ammonium sulphate solution witli the sulphate of nickel, and make up with water to one gallon. In working nickel solutions, they become too acid when insufficient anode surface has been pro- vided. To correct this excess acidity, add liquor ammonia in small quantities until the solution ceases to redden blue litmus paper. When a solu- tion ceases to deposit white nickel, a very small quantity of common salt is added, say \ oz. to the gallon of solution. Messrs. Hartley point out that if the nickel solution be weak, it offers too much resistance to the flow of the current ; whilst if it is too acid, the deposit is pulverulent and peels off. The brilliant whiteness of American nickel plating is due mainly to the quality and purity of the salts NtCKEL-PLATING AND CyCLE-PLaTING, tZQ used. A slightly acid bath is best for iron, this giving a beautiful white deposit, whereas an alka- line or neutral solution gives a darker shade. A yellow sediment in the plating solution is due to the bath being too alkaline. Litmus paper for testing the solution should be kept handy ; an acid solution turns blue litmus to red ; an alkaline solution turns red litmus to blue. The use of cast nickel anodes soon causes a bath to become alkaline. A form of hydrometer with a heavily loaded bulb at the bottom can be used if desired for testing a nickel-plating solution, the instrument being appropriately termed a nickelometer. To test a solution pour a quantity into a testing glass (any long, slender glass vessel will do) and gently lower the instrument into the sample. The nickelo- meter has a graduated stem, and the nickel solu- tion should not register less than seven degrees on this. If it does, more nickel salts must be added until the density of the solution is correct. Nickel anodes should invariably be made of pure rolled nickel plates of a thickness suitable to the work in hand. Small anodes for small operations should be thin, the thickness increas- ing with the superficial size of anode required. Plates of cast nickel are always clumsy, because heavy and thick ; they are also brittle and porous, whilst the pores are apt to contain impurities. Loose carbon, in the form of graphite, has been found interspersed with badly cast nickel. Rolled- nickel anodes give off the metal constantly and steadily ; they do not become soft or fall to pieces while in the bath as cast-nickel anodes do ; they may be light and thin to begin with, and they last a long time. Anodes of nickel may be suspended from strong hooks of copper, inserted in holes punched or drilled in the nickel plates. A suit- able hook is illustrated by Fig. 5 (p. 19), but Messrs. Canning and Co. offer the hook shown by I30 Electro-pla ting. Fig. 62 as an improvement. This slides along the rods, and is very secure. It is advisable to coat all cycle fittings with copper before placing them in the nickel-plating \'at. Copper will adhere firmly to all metals if properly deposited, and fill in all cracks and blemishes, whilst nickel will adhere well to copper. It therefore performs the part of a solder in miiting nickel to other metals. Nickel may be de- posited firmly on iron and steel without the help of copper, but the process demands more skill, and the beginner does not produce such good results as when a coat of copper is first deposited on the fittings. The matter is fully discussed on pp. 90 to 92. Copper may be readily de- posited on iron and steel from an acid solution of sulphate of copper, but the deposit of copper thus obtained will be useless for the present pur- pose, because it will not adhere firmly to the plated articles. When copper is deposited on iron and steel from an alkaline solution of copper, the deposit has a fine grain, and is firmly adherent to the article. The best alkaline solution for cycle plating is made as follows: — Esti- mate ^ lb. of copper sulphate for each gallon of solution required, and dissolve this salt in enough hot rainwater to form a solution. This will be about half a gallon of water to each pound of salt. Set this aside to cool, and when cold, add enough liquid ammonia, whilst stirring with a stick, first to throw down the copper in the form of green mud, and then dissolve this to form a beautiful blue liquid, free from sediment. Add to this enough cyanide of potassium dissolved in rainwater to destroy all the fine blue colour, and give the colour of old Fig. (;2. Improved Hook for Nickel Anode. Nickel-plating and Cycle-plating. 131 ale to the solution. The quantity of liquid ammonia and of cyanide of potassium cannot be definitely stated here, as these materials vary very much in strength and quality ; hence, it is safest to follow the above colour indications, being careful to stir the solutions well after each addition of ammonia and of cyanide. For purposes of estimation take equal weights of each salt and the ammonia, as both are used for other purposes, if there should be a surplus. The solution thus formed should be well stirred, allowed to rest for a night, and then filtered through calico into the vat, where it is made up to the required quantity with rainwater. The coppering vat must be furnished with rods, anodes, cables, resistance-board, and other fit- tings, as before mentioned. In preparing new work intended to be plated, the work of the smith and fitter may be found either a help or a hindrance to the polisher and plater. Rough forgings, weldings, and brazings by an unskilled or careless smith cause an im- mense amount of extra labour to the plater's pol- isher. It may be stated emphatically here that all notions respecting the filling up and covering over properties of nickel are entirely erroneous and false. Nickel will not fill up cracks and deep pits, cuts, or file marks ; it will not cover defective forgings and rough welds. If the fitter does not file these out, they will be shown in the finished work, unless the polisher grinds out the flaws on the emery-wheel, and thereby weakens the part ; thus a defective machine is the result of a pol- isher's attempt to make good the faults of the smith. The smith should therefore aim at turn- ing out his part of the work in as smooth and finished condition as he can. The fitter should also be careful to avoid bruising or denting the surfaces of the parts, and leaving rough file-marks on them. He also should aim at turning out the 132 Electro-pla ting. machine in a finished condition, remembering that the polisher's duty is to put on a higher finish, but not to make good the fitter's defects. The preparatory polishing of iron and steel parts of cycles may be done by hand with different grades of emery-cloth, but the work is best done in a polishing lathe or on an emery tape machine (see Chapter III.). When it is known that the surfaces of parts to be nickel-plated must be made as smooth and bright as iron and steel can be made before they are plated, the use of a machine to do this will be appreciated. The smallest scratch left by the smoothing file, or even by fine emery-cloth, will be plainly visible in the nickel coat even when this has been polished, for nickel is too hard and intractable to be scratch- brushed and burnished like copper, silver, or brass. If the forgings are rough, the rough parts must be taken down on an emery-wheel fastened to the spindle of the polishing lathe between suitable collars. Some skill is required in the use of these powerful tools, as they soon grind and cut their way into wrought-iron. The work must therefore be kept w^ell alive in front of the wheel, and not allowed to lie long enough for the emery to cut into the metal. Different shapes and sizes may be necessary to suit different forms of parts. When the rough patches are reduced, the work must next be submitted to the action of an emery- bob. If the work is not very rough, an emery- bob may be used from the first. For cycle work it is advisable to have an assortment of bobs, varying from 12 in. in diameter down to 9 in., 6 in., and 4 in., and in various thicknesses, from 2 in. to 1 in. ; also some solid bobs made of bull- neck or sea-horse, some of them only \ in. in thickness, and turned round on their edges to fit curves and hollows (see Fig. 34, p. 65). Coarse Nickel-plating and Cycle-plating. 133 grain emery, such as No. 90, is used on bobs in- tended for the first grinding, then No. 120, or a finer grade, to take out marks made by the first ; then the work must be finished off or "coloured'' with flour-emery on a plain uncoated bob. The flour-emery must be mixed with a little oil, just enough to keep it from flying about, and allowed to pass between the work and the bob whilst this is revolving. The bobs are made to revolve toward the work- man, who stands in front, a little on one side, and holds the work to the revolving bob. The work must be kept well alive whilst polishing- that is, must be kept in continual movement, either from side to side or round and round in front of the bob, to prevent lines from being cut in the metal. It is somewhat difficult to guide a novice by instructions on paper, for there are many little acquired knacks known only to the practical polisher, and called up on the spur of the moment to meet some little requirement ; these knacks can only be obtained by practice. Polishing metal is generally designated dirty work, and the workman should protect his clothes by wearing a canvas apron or blouse overall ; but he may avoid much dirt by standing a little out of the line of particles flying off from the bobs. Copper, German silver, brass, and alloys of soft metals are not prepared with emery, but with a fine sand, sold under the name of Trent sand, applied on a clean bob. When the rough surface has been worn down with this sand, it is next subjected to the action of Tripoli composition ap- plied by a calico mop run on the spindle of the })olishing lathe. Tripoli composition is a com- position of Tripoli powder and tallow, and is sold in three grades — A, a fine grade for polishing nickel-plated goods, and putting the finishing polish on German silver, brass, copper, and other soft metals ; b is a grade not so fine as the pre- 1 3 4 Electro-PL A ting. ceding, but will do for the same purpose where a highly-j&nished surface is not desired ; h is a harder and rougher grade, very useful in taking scratches and file-marks out of brass and copper before using the finer grades. These compositions are superior in every way to loose powder for polishing purposes. Surfaces about to be nickel-plated are given the finishing touch with a 9-in. calico mop charged wdth rouge composition, or with rouge powder mixed with water, or with fine powdered lime specially prepared for the purpose, and sold under the name of Sheffield lime. When the articles to be plated leave the pol- isher's hands, they are apparently as clean as it is possible to make them ; not a spot can be seen on the surface, which is clear and bright as a mirror. But this mirror-like surface will not re- ceive a coat of nickel, or, strictly speaking, will not retain the coat even should the plater get it on the article. This surface is coated with a very thin transparent film of animal matter, such as grease or oil, although it may have been finished with rouge and water or wdth lime, and this film will be quite enough to prevent the coat of nickel from uniting with the surface of the metal. Even one little spot in an obscure angle untouched by the scourer, will take on a loose coat of nickel, and form a blister, which will strip in the finish polishing, or after the article has been in w^ear for a few days. When the articles leave the polisher, they must therefore be first soaked in the hot potash solu- tion, to loosen and saponise the film of grease contracted whilst being polished, then rinsed in hot water to remove any loose soap and potash, and passed on to the scouring trough. A hold may be maintained on them during the dipping and rinsing processes by first twisting a stout wire, or two wires, if necessary, around them. Nuts, Nickel-plating and Cycle-plating. 135 collars, rings, and similar articles with holes in them, may be strung on wires, but it is not ad- visable to bunch too many, as they are liable to scratch whilst being rinsed. The work to be scoured is held by the workman in his left hand on the edge of the scouring tray, or on a board provided for the purpose, whilst he scours it all over with a brush dipped in finely- powdered pumice-stone or finely-powdered whit- ing. Whiting is to be preferred, because it is not so rough as powdered pumice. Some workmen peg pieces of buff leather to the edges of the trays and scouring boards, to prevent scratching by the wood. Be sure to scour every little crevice of the article, and leave no part untouched, for it will be just this unscoured part which will strip after being plated. The work requires merely a brisk light brushing. Keep the left hand well coated with whiting, or handle the work with a clean linen rag to prevent soiling by SM^eat, for this will cause the nickel coat to strip. When every part has been well scoured, attach the slinging wires to each article as it is finished, rinse off all the whiting in one division of the trough, then in clean water contained in the next division, then in the hydrochloric dip for a few moments, again in clean water, and transfer at once to the copper-plating vat to receive a coat of copper, after which rinse and place in the nickel-plating vat. After the articles are scoured and rinsed — if made of iron, steel, zinc, Britannia metal, or pewter, and if the work of scouring has been done speedily — they may be transferred at once to the coppering vat. Whilst scouring large articles made of iron and steel, it is almost im- possible to prevent some parts from contracting a thin film of rust ; and this, if left on, would spoil the work by preventing close adherence of the de- posited coat. It is therefore advisable to dip 1 3 6 Electro-pla ting. them for au instant in a solution of hydrochloric acid to remove the film of oxide thus contracted, then rinse them before placing them in the cop- pering vat. The vessel to contain this solution may be made of wood lined with lead, similar in all respects to the plating vat already described. The solution is composed of 1 part commercial hydrochloric acid (spirits of salts) in 5 parts of water. While brass, German silver, gun-metal, and similar alloys are being scoured, they also are liable to become tarnished on exposure to the air. It is therefore advisable to dip them in a solution of cyanide of potassium before placing them in the plating vat. There are not many or very large articles made for cycles in these metals, and so a small stoneware vessel will hold all the solu- tion required for this purpose. The solution con- tains \ lb. of commercial cyanide of potassium in each gallon of water. The cleaned articles are first swilled for a minute or two in this dip, then rinsed, and transferred at once to the plating vat. Copper must be treated in a similar manner. Lead alloys, such as pewter, Britannia metal, etc., are but seldom if ever used in the cycle trade ; when they are used, they are rinsed in the potash tank, and transferred from this direct to the coppering vat. The dynamo must be going, and the vat al- ready connected with it, before the articles are suspended in the nickel solution, for no time must be lost in starting the deposit after the final rinsing. Wherever practicable, each article should be suspended in the bath, so as to have the same quantity of solution above and below it — that is to say, it must be well bel-ow the surface, but not touching the bottom or the sides of the vat. It should also be slung with its surface facing two rows of anode plates — that is, with the nickel anodes all round, but not too close to the article. Nickel-plating and Cycle-plating, 137 The switch on the resistance board should be well over, to include a high resistance when the first article is placed in the vat, then moved to a lower resistance when more articles are put in, because then more current is required. Put in large articles first, then sling smaller articles, such as nuts, collars, and screws, between them. If this order is not observed, the smaller things may strip whilst being polished. Steel should thus be flanked with iron, but it is not desirable to at- tempt plating copper, brass, German silver, and like alloys in a vat with iron and steel. These are best done by themselves. Small goods, when wired together, should have quite \ in. of space between each article, and screws are best wired with fine copper wire twisted around each, to form a long string of them. The work of deposition must go on without in- terruption for a period of from 1^ to 3 hours, according to the class of work to be done. It is sometimes necessary to turn the articles and move the slinging wires to prevent marking by the wires, but the goods should not be taken out ov the solution. When the article has been in the nickel-plating solution long enough to acquire the desired thick- ness of nickel, it is lifted out of the solution by means of the slinging wires, rinsed at once in the hot water tank, and immediately placed in the hot sawdust pan to dry off quickly. This celerity is necessary to prevent unsightly blotches and spots on the nickel-plated surface, as these show after the work has been polished. When a good de- posit of nickel comes out of the vat, it has a creamy white or a dull grey appearance, which passes to a creamy white when rinsed in hot water. Nickel deposited too fast or from an in- ferior solution may have a dirty grey appearance, which does not alter very much even when rinsed in hot water. To remedy this, add from one to 138 El ectro-pla ting. two per cent, of common salt (sodium chloride) to the solution, and stir well together, then allow the disturbed sediment to subside during the next twelve hours. If the solution is allowed to dry on the surface, or if this is touched with the fingers whilst wet, dirty spots will be formed. The dried plated goods are now polished by means of suitable mops, dollies, and polishing materials. Nickel-plated articles may have their surface finished by polishing them with mops and dollies charged with Sheffield lime, with fine Tripoli composition, or with rouge composition. The lime employed for this purpose is a picked material, procured from Sheffield, where it is packed in casks and jars, from which air is ex- cluded, for transportation to other towns. It may be applied in the first place for polishing plane surfaces, together with a little oil, on a buff bob. When the rough surface has been brightened in this way, the bob may be removed, and replaced by a calico mop charged with lime, by holding a lump to it whilst it revolves. A good polish is thus obtained, which may be still further improved by using a dolly made of swan's- down calico, charged with dry lime from a lump held in the hand. An assortment of bobs, mops, and dollies should be kept on hand, including various sizes and varieties in shape, to go easily into curves and narrow grooves. A very good polish can be imparted to nickel by using first a basil leather mop charged with fine Tripoli composition, then a calico mop charged with rouge composition, and finally a swansdown calico dolly charged with rouge. This imparts a fine steely lustre to nickel-plated goods ; but the use of rouge on a lathe for polish- ing nickel-plated and silver-plated work has the disadvantage that the rouge flies about the shop, and gets into cracks and crannies, where the appearance of the red powder is objectionable, Nickel-plating and Cycle-plating. 139 and from which it is with difficulty removed. It also penetrates the clothing of the workman, and gets into his hair. The work must be kept well alive in front of { lie bob, mop, or dolly whilst polishing its surface — that is, it must be kept moving to and fro or up and down all the time, so as to prevent the tool from grinding into one spot, and cutting through the deposit. Special care must be observed when approaching sharp angles, the edges of holes, and sharp corners, as the nickel deposit is soon cut through at these points, and the work spoiled. The aim throughout is to get a bright mirror- like surface on the nickel ; and this is not very difficult if the work has been properly prepared for plating. If, however, the work has not been properly prepared, no amount of labour or skill will enable the finisher to turn out a polished surface ; and for doing the work over again, all the old nickel must be removed. One method of doing this is to steep it for a short time in commercial sulphuric acid, to which is added, from time to time, a small quantity of nitric acid. However, owing to the corrosive nature and fumes of the acid, the nickel is generally re- moved with emery bobs, the work being polished ready for plating at the same time. A large portion of the plating work to be done in repairing shops consists of replating the parts of cycles from which the nickel has been worn. This is not such easy work as plating new fittings, for the old parts are generally worn unevenly, dented, and bruised, and sometimes deeply pitted with rust. From the preceding instructions for plating new work, it will be clearly understood that all parts to be plated must be thoroughly cleaned ; and to do this, it is necessary to take the machine apart wherever a nut can be un- screwed, a screw withdrawn, or a key driven. All nuts, screws, collars, pins, and similar small 1 40 ElectrO'Pla ting, articles, must be done apart from the larger fit- tings. Handles must be removed from handle- bars, and rubber from pedals and brakes, if these are to be plated, since the solutions will spoil all materials made of ivory, bone, horn, wood, rubber, vulcanite, . ebonite, etc., and the hot potash will loosen all handles. The loose dirt may be removed with a wisp of cotton-waste, and stiff grease should be taken off with some of the same waste dipped in turps. All parts to be plated should be thus roughly cleaned before they are sent to the polisher. If several parts of more than one cycle have to be re- plated, the smaller things, such as nuts, collars, pins, and small bolts, should be bunched together, tied with strings, and attached to the handle-bar of the machine to which they belong. As nickel-plated fittings are more or less tar- nished or stained with rust-marks when sent to the plater, it is advisable to first submit them to a leather mop, charged with emery or with coarse Tripoli composition, to clear the surface from stains and rust. It can then be seen whether they have been nickel-plated or not, and measures taken accordingly. If they have not been plated, and are merely polished iron or steel, rusted and stained, the polishing process must go on as for new parts, special attention being paid to rust- marks, which are sometimes very deep. If the parts to be nickelled have been previously nickel- plated, all the previous coat of nickel must Vje stripped off clean before a new coat can be firmly deposited on them. Nickel will not firmly adhere to a coat of nickel, even when freshly deposited and polished: hence the necessity of stripping it off before a new coat is laid thereon. A very thin coat of nickel may be ground off on an emery-wheel whilst preparing the article for polishing, but it is usual to take off nickel by means of an acid which will dissolve this metal Nickel-plating and Cycle-plating. 141 without injuriously affecting the metal on which it is deposited. The stripping acid is composed of sulphuric acid, nitric acid, and water, mixed in the following manner: — In a stoneware vessel, cap- able of holding more than 12 gallons of liquid, first place 2 gallons of water; then add to this, in a cautious manner, 8 gallons of strong sulphuric acid, pouring it into the water in a thin stream, and stirring the mixture with a glass rod. This precaution is necessary, because the addition of this acid to water is always attended with an evolution of heat, and a consequent raising of the temperature of the liquid to almost boiling point. If water is added to the acid, instead of acid being added to water, the mixture will bubble as if boiling, and some of the scalding liquid will be spurted from the surface, with possibly serious results. After the sulphuric acid and water have been mixed, add to the mixture 2 gallons of com- mercial nitric acid, and stir all well together. As the heat generated in a mixture of sulphuric acid and water is liable to crack stoneware ves- sels, a lead-lined tank is preferable to stoneware for mixing the acids in ; but they must be trans- ferred to a stoneware vessel afterwards, because the mixture of nitric acid with sulphuric acid will dissolve lead. It will even dissolve enamel from iron vessels, and then violently attack the ex- posed iron. The articles to be stripped should be first cleaned free from grease and oil, swilled in the potash solution, and then in the hot-water tank, then wired with stout copper wires, and dipped in the stripping acid. If the coat of nickel is thin, it will be dissolved in a few moments. Thicker coats will take several minutes' immersion, and very thick coats may require half an hour's im- mersion. The work must therefore be closely watched, and lifted out occasionally for examina- tion, as each article should be removed from the 142 Electro-pla ting. stripping acid, and plunged at once in clean cold water when the nickel has all been stripped off. As noxious fumes arise from the acid during the stripping process, this should be conducted in the open air, or in a recess provided with a flue and strong up-draught, to carry the fumes off from the operator. After the articles have been stripped and rinsed in cold water, they should be rinsed in hot water, dried in hot sawdust, and then prepared for plating in the manner already de- scribed. The subsequent operations for replating and finishing are the same as for new work. Some notes on the working of nickel-plating solutions will now be given. Nickel-plating solu- tions are always worked cold. The solution is at its proper working strength when it contains 1 lb. of nickel sulphate to the gallon of water. To maintain it at this strength attention must be paid to the anodes and their condition. As a rule, the surface of anodes ex- posed to the action of the solution should exceed by one-half the surface of the goods being plated. The anodes should also freely dissolve in the solu- tion, and therefore should not be too hard. If nickel has been drawn from the solution too fast, it will be liable to become too acid, and this condition may be ascertained by testing it with blue litmus paper, which will quickly redden if acid is in excess. But a slight excess is per- missible when plating iron and steel. An excess of acidity may be corrected by adding a small quantity of liquid ammonia ; but an addition of nickel sulphate wdll be required also if the normal strength of the solution has been reduced. The hydrometer will show this reduction by comparing it with a sample of known correct strength. The readings on the hydrometer scale show the density of the solution, but not its temperature. Sulphuric acid should not be added to a nickel- plating solution without previously testing the Nickel-plating and Cycle-plating, 143 solution with litmus paper and finding it alkaline. Even then the acid should be added in very small quantities, and the solution stirred after each addition, then tested with litmus paper. The same caution should be exercised in adding ammo- nia if the solution is found to contain an excess of acid. Neutral solutions may be employed in plating copper and brass. If slimy yellow feathers appear on the anodes and on the sides of the vat, the solution is foul, deficient in nickel salts and their solvent. To alter this, filter all the solution through good calico, add one fluid ounce of sulphuric acid to each gallon, test for acidity with litmus paper, and add enough liquor ammonia to render the solution neutral. Work with nickel anodes greatly in excess of the surface to be coated. Pinholes in nickel plating are caused by small air bubbles left on the surface of the articles when immersed in the plating solution. These bubbles may be held in pinholes existing in the surface of the metal, or may form on the smooth surface itself. They may be broken by a smart tap on the edge of the article, by shaking it in the solution, or by sweeping the point of a feather over the surface. If the solution holds particles of dust, these may settle on the articles being plated and cause pinholes. To avoid this, keep the solution clean by filtering it occasionally through clean calico. Black streaks in deposits of nickel are caused by bubbles of hydrogen gas, which form in clusters on the surfaces of articles and then burst. They may be prevented by gently agitating the articles whilst being plated, or by stroking the clusters with a stout feather and thus bursting them. All electro-deposits of metal are slightly porous, and so when a thin deposit of nickel on steel or iron is exposed to moisture the tiny drops pene- trate these pores to the metal beneath and cause 1 44 Electro-PL a ting. rust. A thicker deposit offers a better protection, or better still is a coat of copper deposited on the parts and well burnished previous to being coated with nickel. Aluminium may be treated much the same as zinc in preparing it to receive an electro-deposit of nickel or silver. After it has been well scoured with Trent sand, it must receive a coat of copper in a sulphate of copper solution, and be trans- ferred direct from this to the nickel-plating solu- tion. Solutions for nickel-plating on aluminium should not contain any free alkali, but he slightly acid, since alkalis act on aluminium. Nickel can be deposited on wax moulds, but previously the mould must be prepared with black- lead or with bronze powder as for the electrotype process, and a thin film of copper deposited upon it in an electrotype solution (1 lb. of copper sul- phate and 4 oz. of sulphuric acid in 1 gal. of rain- water). If the object desired is a copy of a de- sign impressed on the face of the mould, it will be advisable to remove the mould to the nickel vat when it has become coated with a very thin film of copper, and deposit the nickel on this film. If the design is not undercut, it may be possible to peel off the film of copper from the nickel ; but some difficulty may be experienced in getting a deposit of nickel thick enough to form a plate or sheet, as thick deposits have a tendency to crack, curl up, and peel off. To get a tough coat, the nickel should be deposited slowly with a low-ten- sion current. 145 CHAPTER VIII. FINISHING ELECTRO PLATED GOODS. Properly electro-deposited silver leaves the plat- ing solution with a pleasing, rough, creamy-white surface, much like fine unglazed porcelain. It should be rinsed in clean hot water to free it from silver salts, and may be dried in clean hot box- wood sawdust, or scratch-brushed first, then washed in warm soapsuds, rinsed, and dried to prepare it for the polisher. Great care must be taken of the surface, as it is easily soiled and readily tarnished, and then causes much trouble to the polisher and finisher, who will have some difficulty in cleaning the surface. The rinsing waters must therefore be clean, and the sawdust free from dirt and burnt or brown particles. Should the article have a yellowish tinge when taken from the vat or from the hot sawdust, swill it at once in a warm dilute solution of potassium cyanide and rinse and dry If the silver-plated surface is to have a higher polish than that imparted by scratch-brushing, it must next be held against a revolving swansdown mop charged with fine rouge. This may be applied in the form of powder to a mop previously greased or oiled ; but rouge compositions do the work better, and in working are far more cleanly than powdered rouge. Avoid rubbing the silver off angles and projections, and apply pressure moderately, the surfaces being kept moving to and fro to prevent the mop cutting into one spot. This movement is specially necessary when polishing the coat on soft metals, to prevent blistering, as 146 Electro-plating. the heat generated by friction is liable to cause buckling of the underlying metal. Deeply impressed or engraved designs to be highly polished must be held against a revolving hair-brush charged with rouge powder. AVhen a sufficiently high polish has been ob- tained, it is advisable to wash out any rouge that may have lodged in crevices by steeping the articles in hot soapy Avater and mopping with a soft woollen mop. After this they should be rinsed in hot water and dried, then mopped with a clean swansdown mop. With great care in keeping mops free from grit, dust, dirt, etc., and the use of best quality compositions, a high lustre can be got on silver-plate by mopping alone. If the deposit blisters and breaks away whilst being scratch-brushed, the loose silver must be all got off, either by means of a rough bob or in a stripping solution, and the surface again pre- pared by polishing, scouring, and quicking as before. The thin preparatory coat may be thus ground oft" easily without blotching the surface ; but if the deposit blisters at a later stage it will be necessary to strip off all the silver in acid and begin afresh to get a good surface. The articles to be stripped must be quite dry and attached to stout wires, then gently moved in ordinary un- diluted sulphuric acid made hot in a stoneware vessel, and grain saltpetre added in small quan- tities at a time until all the silver has been dis- solved. If this is done carefully the acid will do very little injury to the article. For large articles a cold stripping solution may be employed ; this is composed of sulphuric acid with a little nitric acid added from time to time as required. Small articles, such as buckles, buttons, metal beads, hooks and eyes, etc., are treated in a special manner in preparing, silvering, and finish- ing. They are prepared by shaking some hundreds at a time with grit and sawdust in a revolving Finishing Electro-plated Goods. 147 barrel or in a stout sack. If it is necessary to pickle them, they are massed together in a per- forated acid-proof vessel and shaken in this whilst immersed in the pickles and rinsing waters. Whilst being plated they are held in a basket made of brass or copper wire, and this is also to be kept moving by shaking to prevent contact for a long time ; if this is not done, the articles will be blotched where they touch each other. By automatic machines the articles are so kept in motion whilst being plated that they are in a polished condition when the silvering is finished. If these machines are not employed, the articles must be rinsed and dried, and then polished by shaking together with sawdust or bran. With regard to finishing gold-plated work, strongly gilt articles just taken from the gilding solution will be found to be coated with a brown powder. This powder is finely divided gold in a crystalline condition, the mass of crystals absorb- ing, instead of reflecting, the light. To remove tliis brown appearance, the articles are briskly scratch-brushed, the scratch-knot lathe being a convenient appliance for this purpose. The ends of the brass wires wear down the points of the gold crystals, and render the whole surface smooth. To prevent the brass from wearing off in the shape of dust and cutting the gold coat, Ihe brush is kept lubricated with stale beer, and is covered with a hood, to prevent the lubricant from being splashed over other things in the workshop. Rest the w^ork on a sloping piece of board over a vessel placed so as to catch the drips of stale beer, and work the brush from left to right, away from the workman, going over all the surface until all the brown appearance has been removed. Do not leave any of this in the crevices. Lastly, rinse the work in warm water, and dry it in hot box- wood sawdust. Then polish with dry rouge on a plate brush, or burnish w^ith a highly polished steel 1 48 Electro-pla ting. burnisher, or one of highly polished bloodstone, using newly made soapsuds as a lubricant. Stale beer, as stated on the preceding page, is employed as a lubricant whilst scratch-brushing electro-plated articles. Unless a lubricant is used, the brass of the brush wire gets worn off as fine dust and becomes embedded in the surface of the plated article, rendering it more or less brassy in appearance. A tea made of marsh mallows, or weak linseed tea, can be used instead of the beer. A still higher polish on electro-plated work re- sults from the use of steel, agate, and bloodstone burnishers. These tools are made in a large variety of shapes to suit all possible surfaces. The steel burnishers have very highly polished rubbing surfaces, which must be maintained in this condition by frequent rubbings on a pad of buff leather charged with putty powder. Skill in burnishing is acquired only by practice. The article is held on a soft pad with one hand, whilst the burnisher is held firmly by its handle with the other hand, and pressed hard on the surface with uniform straight strokes slightly overlapping each other. The surface of the burnisher may be kept moist with soapsuds, made either Avith best soap or with special burnishing soap. After the steel burnishing, the finish is imparted with either agate or bloodstone burnishers, and the whole article afterwards rinsed in hot water, then dried by rubbing with a soft linen cloth free from dust. The mirror-like surface of burnished silver is easily scratched and soiled, and should not be wiped or handled more than necessary. Soft metals, sucli as pewtoi', must be burnished very lightly, if at all. Burnishers in their least expensive form are made of steel blades varying in shape, running into the wood. Straight burnishers, shaped as shown at Fig. 63, and in section at A, are used for burnishing stems of spoons and forks, and plane surfaces generally. Curved burnishers, such as Finishing Electro-plated Goods. 149 those shown in Figs. 64 to 68, and in section at B, c, D, E, and F, are used for burnishing the insides of the bowls of spoons and for hollow curves. Burnishers made of chips of agate, and of bloodstone or haematite, set in brass ferrules and mounted on wood, are more costly than those made of steel, and they also impart to the goods a more finished surface. Some further forms of ^" ^) c Fig. 63. Fig. (U. Fig. C. Fi