NICKEL-PLATING. Ill 



become polished after being coated. M. Pfanhauser, a great 

 advocate of nickel depositions, objects to this notion so as not 

 to deceive beginners, and says with reason that the final ap- 

 pearance of the object solely depends on its degree of polish 

 before putting it into the bath. If it is dull, rough, or polished, 

 it will come out dull, rough, or polished. It is therefore 

 essential to prepare the pieces in the same way as it is desired 

 to have them after immersion, so that after a single cleaning 

 only they may be ready for sale. 



The Viennese polishers, who are renowned for the finish 

 given to their work, use in the first operation lime-wood disks 

 provided with leather impregnated with glue and sprinkled 

 with polishing powder. 



For fine polishing they use disks made of several layers of 

 cloth soaked with stearic oil and sprinkled with lime reduced 

 into impalpable powder. 



The velocity of the disks reaches 3000 revolutions per 

 minute, and as these have a diameter of 30 centimetres, there 

 results a speed of 50 metres per second at the point of contact 

 of the brushes with the pieces. 



Brass, bronze, or copper pieces are first polished, then 

 scoured in a boiling lixivium of caustic soda. Care must be 

 taken to wrap the pieces with a copper wire so as to manipulate 

 them without touching them, as a mere contact with the fingers 

 would grease them. They are afterwards dipped into pure 

 boiling water, rinsed, and brushed in cold water until perfectly 

 free from grease. 



This operation can be carried out cold by washing and 

 brushing with lime cream. 



After cleansing, the pieces should be kept for a very short 

 time in a tepid solution of potassic cyanide, so as to eliminate 

 the oxidisation which has taken place on the surface of the 

 metal. There only remains to rinse them in a few clean waters 

 to enable them to efficiently receive the coating of nickel. M. 

 Pfanhauser recommends in a specjal manner that the pieces 

 should not be allowed to become dried by the air ; as soon as 

 they are prepared, they must be put in the bath. 



When steel, cast iron, or iron objects are submitted to the 



