I 



Manufacture of Tin-pJate. 143 



are conveyed to a furnace heated red-hot, where they remain 

 until the heat takes off the scale, the removal of which was the 

 object in submitting them to that high temperature. 



When this is effected, the plates are taken to a floor, where 

 they are suffered to cool — they are then straightened, and beaten 

 smooth upon a cast-iron block. The workman knows by the 

 appearance of the plates during this operation, whether they 

 have been well scaled — for if they have, that is, if the rust or 

 oxide which was attached to the iron, has been properly removed, 

 they will appear mottled with blue and white, something like 

 marbled paper. The operation we have been describing is called 

 scaling. 



As it is impossible the plates can go through this process 

 without being in some measure warped, or otherwise disfigured, 

 they are now rolled a second time, between a pair of cast-iron rol- 

 lers, properly hardened and finely polished. This operation makes 

 both sides of the plates perfectly smooth, and imparts a sort of 

 polish to their surfaces. These rollers are each about 17 inches 

 long, and 12 or 13 inches in diameter — but I am inclined to think 

 that if the diameter was greater*, they would set the plates 

 flatter, and do the work better in every respect. 



The technical name of this apparatus is rolls, notrollers. All 

 the rolls which are employed in rolling plates, either hot or cold, 

 in this manufactory, &vehard rolls — and there is as much difl^er- 

 ence between a pair of hard cast-iron rolls, and a pair of soft 

 rolls, although they may both be run out of the same pot of 

 metal, as there is between iron and steel. The workmen inform 

 me that the difference is entirely occasioned by the manner of 

 casting them — the soft rolls being cast in sand, whereas the 

 hard rolls arc formed by pouring the metal into a thick cast-iron 

 box— and that the metal, by coming in contact with the cold box 

 is sufficiently chilled to render the whole face of the roll entirely 



* Since tlie above was written, I have submitted the niauuscript to a 

 gentleman who is very largely engaged in the manufactnre of tin-plates, 

 and he tells inc that the cold rolls which are employed in his work, are ,10 

 inches in diameter. 



