126 ELECTRO-PLATING. 



Protection of Silver Surface. All silver or plated articles are 

 subject to tarnish by exposure to the air, especially in this climate, 

 and where coals containing so much sulphur are used ; the tarnish 

 being generally a sulphuret of silver. Deposited silver is more 

 easily tarnished than standard silver. 



Medals or figures silvered for the sake of their appearance ought 

 to be protected from the air, or they very soon lose their silver 

 colour : a medal may be put into a frame air-tight, and a figure 

 should be covered with a glass shade : if the silver has been left 

 dead, any attempt to clean it destroys its appearance. Varnishes 

 have been tried to protect the silver from the atmosphere ; but all 

 varnishes, however colourless, detract from the silver lustre, and are 

 not good. For ordinary purposes, medals may be very conveniently 

 protected by laying a piece of common glass over the surface, cut to 

 the exact size, and held close by a piece of paper pasted round the 

 edges of both, and then a stout piece on the back. We have had 

 silver medals, preserved by this means, for more than six years. 

 Little round medals may be conveniently covered by watch-glasses, 

 fastened on in the same manner. 



Cleaning of silver A weak solution of cyanide of potassium, 

 used as a wash over tarnished silver, will brighten it. This solution 

 was sold in small bottles for this purpose, but it is not good, as it 

 dissolves the silver rapidly, and is such a deadly poison that it must 

 be used with great caution on articles that may be required for do- 

 mestic purposes. 



A variety of cleaning pastes and powders are used for silver or 

 plated goods. Those containing mercury and oxide of lead should 

 be avoided, for although they give a dark colour when newly put 

 on, it soon blackens. The best paste we have found is a mixture of 

 fine precipitated chalk, carbonate of magnesia, and oxide of iron. 

 These materials are made into a paste, and rubbed upon the 

 plate with soft leather: for wrought or chased surfaces a hard 

 brush is best. The goods should be finished by polishing with 

 leather and a little of this mixture in a dry state, which will give 

 that fine dark mirror-looking colour so much admired. Common 

 coarse whiting and flannel cloths should not be used, as they wear 

 the silver rapidly. 



