PROTECTION OF SILVER SURFACE. 125 



ceased, which will not be before a considerable time, and when all 

 the mass seems to have been acted upon, the process of making an 

 excellent protecting coating is completed, a coating which will not 

 yield in the solution, and which is at once both good and cheap, its 

 only fault being its brittleness. 



In the manufacture of solid silver articles, the electro-process has 

 not yet been of extensive application ; and in making duplicates of 

 rare objects of art, and costly chased or engraved articles in silver, 

 one prevailing and as yet insurmountable objection has been felt, 

 namely, they have no " ring," and seem, when laid suddenly upon 

 a table, to be cracked or unsound, or like so much lead ; this dis- 

 advantage is no doubt partly owing to the crystalline character of 

 the deposit, and partly to the pure character of the silver, in which 

 state it has not a sound like standard or alloyed silver. That this 

 latter cause is the principal one, appears from the fact that a piece 

 of silver thus deposited is not much improved in sound by being 

 heated and hammered, which would destroy all crystallization. 



We may mention that the same objections are applicable to 

 articles made in gold by the electro -deposit ; nevertheless, for figures 

 and ornaments these objections are of little weight. 



Dead Silvering for Medals. The perfect smoothness which a 

 medal generally possesses on the surface, renders it very difficult to 

 obtain a coating of dead silver upon it, having the beautiful silky 

 lustre which characterises that kind of work, except by giving it a 

 very thick coating of silver, which takes away the sharpness of the 

 impression. This dead appearance can be easily obtained by putting 

 the medal, previous to silvering, in a solution of copper, and deposit- 

 ing upon it, by means of a weak current, a mere blush of copper, 

 which gives the face of the medal that beautiful crystalline richness 

 that deposited copper is known to give. The medal is then to be 

 washed from the copper solution, and immediately to be put into 

 the silver solution. A very slight coating of silver will suffice to 

 give the dead frosty lustre so much admired, and in general so 

 difficult to obtain. 



Oxidising Silver. A very beautiful effect is produced upon the 

 surface of silver articles, technically termed oxidising, which gives 

 the surface an appearance of polished steel. This can be easily 

 effected by taking a little chloride of platinum, prepared as described 

 at page 41, heating the solution and applying it to the silver, 

 where an oxidised surface is required, and allowing the solution to 

 dry upon the silver. The darkness of the colour produced varies 

 according to the strength of the platinum solution, from a light steel 

 grey to nearly black. The effects of this process, when done along 

 with what is termed dead work, is very pretty, and may be easily 

 applied to medals, giving scope for the exercise of taste. 



