346 The Art of Electro -plating and Gilding. 



preparation, and a brush as stiff as a tooth-brush may be used 

 upon them without injuring the impression. 



Supposing the surfaces of the mould to have been properly 

 prepared, another point of at least equal importance is the 

 attachment to them of conducting-wires, by means of which the 

 mould may be connected with the battery apparatus. Little 

 instruction is here needed : the electric fluid passes along the 

 metallic wire readily enough, and when once it reaches a well- 

 prepared conducting surface, its diffusion over every part of it 

 may be relied on. The main point, therefore, is the perfect 

 union of the two. In wax, sulphur, or gutta percha, the wires 

 are easily fixed by heating their ends, and then pressing them 

 into suitable parts of the mould. To fix them into plaster of 

 Paris, small holes must be bored in the cast, and the wires 

 fixed into these with wax or cement. Then, to render the 

 metallic connection perfect, blacklead is rubbed on to the joint 

 freely, and finally brushed up to the well-known polish. 



Another mode of rendering surfaces conductuous is often 

 resorted to, and, though a little more tedious at first, is on the 

 whole more effective. A piece of phosphorus is dissolved in 

 about twenty times its weight of bisulphide of carbon ; in 

 another vessel a solution of nitrate of silver is prepared. It 

 need not be saturated ; or, if a saturated solution is prepared, 

 it may be diluted with about two or three times its bulk of 

 water. The cast is immersed for a minute or two, first in the 

 phosphorus solution, and immediately on its removal from this 

 is placed in the solution of nitrate of silver. The action of the 

 phosphorus on the silver salt is so energetic that, in a few mo- 

 ments after it has been removed, and left to dry under the 

 action of daylight, the metallic silver is separated from its 

 combination, and forms an exceedingly thin metallic surface to 

 the cast. The inexperienced operator must not be deceived by 

 appearances here, for he will be deceived if he looks for silver 

 in the form in which it commonly presents itself to his notice. 

 Silver, when deposited from its solutions by this method, is 

 blach, and an unbroken black surface is the best evidence he 

 can have that his experiment has succeeded. 



Nor must a deposit on a surface prepared as above be ex- 

 pected so promptly as on surfaces purely metallic. A deposit 

 often appears in the neighbourhood of the conducting- wire in the 

 course of an hour or so after immersion, but even then it will 

 sometimes take several hours to complete the coating over every 

 part of the cast. When once the coating is complete, however 

 thin it may be, the further deposition of course proceeds rapidly. 



As to the battery apparatus to be used in these latter ex- 

 periments, it will suffice to state that the forms described for 

 medallions and coins -will answer Gqually well for these. 



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