NICKEL-PLATING. 129 



are used, and finally a disk of wool, which gives a shining 

 brightness. 



The hollow parts are polished by means of a small rotary 

 top, lined with cloth and sprinkled with polishing powder. The 

 polished objects are washed freely in water, so as to rid them 

 of the traces of wool and powder, and then dried in hot sawdust. 



This polishing work is often neglected by the nickel-platers ; 

 it is, however, very cheap, and gives the pieces a shining ap- 

 pearance which enhances their value. The polishing of small 

 objects nickeled in block is effected in a long and strong linen 

 sack or in a revolving drum containing sawdust. Or they may 

 be polished by vigorously brushing them with hot water and 

 soap with the addition of a little ammonia. 



Under certain circumstances the coating may be swollen, 

 flaky, or scaly, notwithstanding the greatest precautions taken 

 with a view to obtaining good results. This may happen, for 

 instance, when the galvanometer is disturbed and a current too 

 strong and of too great duration has been sent through the 

 bath. If the coating cannot be perfected by following the 

 foregoing prescriptions, it must be taken off, and the whole 

 series of operations gone through again ; this is what we call 

 renickeling. 



KENICKELING. Eenickeling is never a pleasant operation 

 for the nickel-plater, but as it constitutes an important and 

 necessary item in his industry it is necessary to acquaint him 

 with the best means of proceeding. 



Messrs. Watt and Elmore have treated this question with 

 great detail, and we think it advisable to recommend their 

 process, which is as follows : 



The first operation in renickeling damaged pieces consists 

 in stripping, by means of acids, the old coating from the piece. 

 This is absolutely necessary, for the metal does not firmly adhere 

 to the original coating. The following solution will generally, 

 after a very short immersion of the pieces, take away from 

 them all trace of nickel : 



Sulphuric acid .. .. 4 litres. 



Nitric acid 500 grammes. 



Water 500 



Potassic nitrate 50 



