Popular Science Monthly 



Make up another solution- of I oz. 

 of the cyanide salts in a quart of pure 

 water and pour enough of this over the 

 washed precipitate to dissolve it, stirring 

 well. When a clear, colorless liquid results, 

 add more of the cyanide solution as there 

 must be a slight excess of cyanide in the 

 plating bath. Add enough water to give 

 the desired quantity or strength. 



If pure silver nitrate can be obtained, 

 it may be used instead of the metal solution. 

 Pure nitrate will contain approximately 635 

 grains of the metal in each 1000 grains of 

 the salt. 



A very good solution for ordinary work 

 can be made by dissolving 1 oz. of pure' 

 silver nitrate in 40 oz. of water and pro- 

 ceeding as above to throw down and wash 

 the precipitate and redissolve it in the 

 cyanides. By adding two quarts of water, 

 it is ready for use. 



Preparing the Article to Be Plated 



Having prepared the apparatus and 

 solutions, the preparation of the work 

 to be plated is next in order. Plating will 

 cover no defects, such as stains, scratches, 

 etc., but is likely to make them more 

 prominent. Every blemish should be re- 

 moved with a file or emery paper and the 

 surface polished. 



To remove corrosion from brass, copper, 

 etc., soak the article in a. solution made by 

 adding — a little at a time with free stirring 

 1 — 3 oz. of sulphuric acid to 4 oz. of water, 

 and when this has cooled, pour in 1^ oz. 

 of nitric acid. Be sure to add the sulphuric 

 acid to the water a little at a time, allowing 

 it to mix and cool before adding more, 

 finally adding the nitric acid. Soak the 

 work to be cleaned in this solution until all 

 the corrosion is dissolved, or softened so 

 that it may be removed with a stiff brush; 

 then rinse thoroughly and polish. The 

 time required to remove corrosion will vary 

 from a few seconds to an hour or more. 



Those parts which are to have a polished 

 appearance when finished must be well 

 polished before they are plated. This may 

 be done in any way convenient. To use a 

 polishing lathe or stand is the best method. 

 Cloth disks, from 3 in. to 6 in. in diameter 

 and l /2 in. to 1 in. thick may be made, some 

 of canvas or other heavy, hard cloth, and 

 others of flannel or muslin for the finishing 

 touches. They should be used with 

 powdered abrasives, using emery for the 

 rougher operations and finishing with fine 

 polishing powders and soft disks. If a 



637 



lathe is not at hand, use brushes, and cloths. 



When the work has been polished it 

 should be washed thoroughly so that 

 no traces of the polishing materials re- 

 main. After polishing and washing, the 

 articles should be attached to the slinging 

 wires so that they need not be touched by 

 the hands again. Soak the work a few 

 moments in a hot solution made of a table- 

 spoonful of potash in a pint of water. This 

 is the potash "dip" and is to remove all 

 traces of grease and dirt that may have 

 been left. 



After being given the potash dip the work 

 is laid on a board where a small stream 

 of water may flow over it while it is 

 brushed with a stiff bristle brush, kept 

 wet and occasionally dipped into pow- 

 dered pumice stone. This will remove all 

 the potash and grease and also give a 

 slight grain to the surface of the plated 

 article. 



After scouring, rinse the work well in 

 running water and soak for a few seconds 

 in a solution made by dissolving an ounce 

 of potassium cyanide in a pint of water 

 and hang at once in the plating bath. 

 Have the anode in position and the battery 

 connected before hanging the work; other- 

 wise the cyanide in the bath will attack 

 the metal and injure the bath. The article 

 will become white in a moment and a plate 

 of silver will be deposited in from ten to 

 fifteen minutes. 



The Finishing Touches 



When plated heavily enough, the article 

 should be taken from the bath, rinsed in 

 boiling water and dropped into fine, warm 

 sawdust to dry. Exposure of a freshly 

 plated surface to the air and light while 

 it is covered with a film of the plating solu- 

 tion, will cause it to turn yellow. When 

 dried in the sawdust, it should be brushed 

 and will appear a frosty white. 



The first finishing is scratch brushing. 

 A small brush wheel of fine brass wire 

 is held in a lathe or polishing stand, and 

 kept wet with stale beer or oatmeal 

 water. The plated surface is held against 

 it. Without a machine a bristle brush may 

 be used, if stiff enough. When all the 

 chalky whiteness has disappeared and the 

 metal shows an even, dull color, give it 

 another rinsing in plenty of water and dry. 

 It is now ready for buffing and polishing 

 with soft materials, light pressure and fine 

 polishing powders. 



If an extra heavy and durable plate 



