On the Manufacture of Tin-plate. 367 
being re-dipped, the hot grease would take 
off what remained. 
The only use of the grease-pot is to take 
off any superfluous metal that may be upon 
the plates—but this is an operation that re- 
_ quires great attention, because, as the plate 
is immersed in the grease while the tin is in 
a melting, or at least in a soft, state upon it, 
apart must run off, and the remainder become 
less and less while the plate continues in it ; 
therefore, if these plates should ever be left 
in the melted tallow longer than is absolutely 
necessary, they will doubtless require to be 
dipped a third time in the tin. On the other 
hand, if the plates were to be finished with- 
out passing through the grease, they would 
retain too much of the tin, which would be 
a loss to the manufacturer; and besides, the 
whole of the tin would appear to be in waves 
upon the iron. 
It is also equally necessary to attend to 
the temperature of the melted tallow, which 
must be colder or hotter in proportion as the 
plates are thicker or thinner ; forif, when the 
tallow is of a proper temperature for a thin 
plate, a thick one was to be put into it, it 
would come out, not of the colour of tin as 
it ought to be, but as yellow as gold. The 
reason of this is evident. The thick plate 
contains more heat than a thin one, and con- 
