Tin. 
379 
tinning iron, is to hinder it from becoming rusty ; and it 
is a question of some importance, whether iron of a great- 
er thickness than the plates we have been speaking of, 
might not be advantageously tinned, I desired a work- 
man to break off the end of a large pair of pincers, which 
had been long used in taking the plates out of the melted 
tin ; the iron of the pincers seemed to have been pene- 
trated through its whole substance by the tin ; it was of 
a white colour, and had preserved its malleability. It is 
usual to cover iron stirrups, buckles, and bridle bits, with 
a coat of tin, by dipping them, after they are made, into 
melted tin ; and pins, which are made of copper wire, 
are whitened, by being boiled for a long time with granu- 
lated tin, in a lye made of alum and tartar. Would the 
iron bolts used in ship building, be preserved from rust- 
ing by being long boiled in melted tin ? — Would it be 
possible to silver iron plates by substituting melted silver 
for melted tin ? I do not know that this experiment has 
ever been tried ; but an intelligent manufacturer will see 
many advantages which would attend the success of it. 
It is customary, in some places, to alloy the tin, used 
for tinning iron plates, with about one seventieth part of 
its weight of copper ; foreigners make a great secret of 
this practice ; I do not know whether any of our manu- 
facturers use copper, some of them I have reason to be* 
lievedonot. Too much copper renders the plates of a 
blackish hue, and if there is too little, the tin is too thick 
upon the plates ; but this thickness, though it may ren- 
der the plates dearer, or the profit of the manufacturer 
less, will make them last longer. When the tin is heat- 
ed to too great a pitch, some of the plates have yellowish 
spots on them ; but the coat of tin is thinner, and more 
even, when the tin is of a great, than of a moderate heat ; 
and the yellowness may be taken away, by boiling the 
plates for two or three minutes in lees of wine, or, where 
Vol. HI. 3 A 
