364 On the Manufacture of Tin-plate. 
The drawing represents the surface of the 
pots. The asterisks shew the places where 
the workmen stand, and also mark those pots 
which have heated flues under them. No. 4. 
has no fire under it. 
The parting in the wash-pot No. 2, is a 
late improvement. The design of it is to keep 
the dross of the tin from lodging in that part 
of the vessel where the last dip is given to. 
the plates. By using the common tin in the 
first process of tinning, much oxide, or dross, 
adheres to the surface of the plates, and this 
runs off in the wash-pot, and comes to the 
face of the new metal—but this parting ena- 
bles the operator to prevent it from spreading 
over the whole surface of the pot. Were it 
not for this parting, the wash-man must skim 
the oxide off the fluid metal every time he 
puts plates into it. 
The pots of which I have given a sketch 
being all in a state of fitness, the wash-man 
commences his part of what remains of the 
business, by putting the plates which have 
undergone the various operations hitherto 
described into the vessel of grain-tin, called 
the wash-pot.* The heat of this large body 
* None but grain-tin is ever put into this vessel, for 
the whole of the common tin which is consumed in such 
