NICKEL-PLATING. 125 



delivered, and the whole of the work has to be gone through 

 again ; sometimes even the nickel is seen to peel off without 

 being touched and without a possibility of any remedy. It 

 must be added in justice that a moderately thick coating lasts 

 a few years, even with objects frequently in use, owing to the 

 quite exceptional hardness of the nickel. 



It is, however, not difficult to obtain a thick coating. When 

 the bath is duly composed, the anodes well placed, and the cur- 

 rent properly regulated, a deposition of two grammes of nickel 

 per square decimetre can easily be effected, which corresponds 

 to a thickness of coating equal to a fortieth of a millimetre. It 

 is not much when the masses of the articles, some of them of 

 daily use, are considered ; it is sufficient when these coatings are 

 compared to those of silver, so appreciated in every country. 

 The average thickness of silver-plating executed by the best 

 electroplaters, does not exceed three grammes per square deci- 

 metre, and as the density of silver exceeds that of nickel, it 

 may be concluded that it is not fair to reproach nickel-plating 

 on account of its thinness. 



The truth is that, by means of successive operations of 

 polishing and putting in bath, nothing prevents giving the 

 nickel coating any desired thickness ; the exceptional hardnes 8 

 of the metal alone renders useless such a series of manipulations 



From a commercial point of view, three kinds of products 

 may be considered : 1st, articles having a bright polish ; 2nd, 

 rough articles ; 3rd, cheap fancy articles. 



Bright polished articles are left in the bath with a suit- 

 ably regulated current until the coating turns bluish grey, 

 slightly dull ; they are then taken out and rinsed first in cold 

 water, then in boiling water, and are finally dried in sawdust. 

 The solidity of the coating can be ascertained by sharply and 

 vigorously rubbing an angle of the nickel-plated object 

 against a well planed pine board, and this until the object 

 becomes very hot ; if the nickel-plating stands the ordeal with- 

 out being injured, it can be considered as excellent. 



Bough unpolished metallic objects are also left in the bath 

 until they acquire a dull bluish-grey hue. The adherence 

 of the deposit is ascertained by scraping with a hand steel 



