XICKKL-PLATING. 115 



Tin-dull scouring obtained by the acid is rendered bright by 

 tin- whiting bath. 



For rough, unpolished castings, M. Perille recommends a 

 few particular operations which gave him some very satisfactory 

 results. They are as follow : 



1. Dip the pieces in an ordinary scouring bath so as to 

 whiten the cast iron, and rinse in water ; 



2. Scrub the pieces by means of an iron wire brush rapidly 

 revolving (about 1200 revolutions per minute), using liquid 

 pumice powder so as to thoroughly clean them. Kinse as 

 indicated after each manipulation ; 



3. Dip the pieces in a copper bath so as to immediately 

 protect them from atmospheric influence, then dry them by 

 passing them through hot water and hot sawdust. 



This latter operation is not absolutely necessary ; we how- 

 ever recommend it because it is cheap, rapidly done, and prevents 

 the oxidation of the pieces which have just been scoured and 

 cleansed. 



Elmores Method. Mr. El more insists upon a preliminary 

 polishing, as perfect as possible, and recommends the use of 

 drums lined with buffalo-leather soaked in Sheffield chalk, oil 

 and tripoli, for the first operation. For removing the file marks 

 or the unevenness, he recommends the use of Trent sand or of 

 glassmaker's sand. After the surface has been smoothed by 

 means of revolving drums thus covered with sand, the pieces 

 are brushed and put through finely pulverised quicklime. 

 Copper, brass, and Britannia metal pieces are finished by means 

 of a circular brush made of a large number of calico disks kept 

 together by leather disks and screws. Steel pieces are smoothed 

 at first by means of an emery wheel, and afterwards by means 

 of leather disks sprinkled with sand. 



Before putting in the bath, Mr. Elmore's plan is to first dip 

 brass and copper pieces in a hot bath of potash, rinse them, 

 put them in the cyanide bath, rinse them again, and put them 

 in the cleaning tub. 



The cleaning must be effected with the greatest care and 

 as rapidly as possible ; it is important to frequently dip in pumice 

 powder the hand which holds the piece. Precaution must be 



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