310 TINNING, PLATING, &C. 



whitened, by being boiled for a long time with granulated tin in a 

 lye made of allum and tartar. Would the iron bolts used in ship, 

 building be preserved from rusting 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 manufacturers use copper ; some of them I have 

 reason to believe do not. Too much copper renders the plates of a 

 blackish hue j and if there is too little, the tin is too thick upon 

 the plates ; but this thickness, though it may render the plates 

 dearer, or the profit of the manufacturer less, will make them last 

 longer. When the tin is heated 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 they cannot be 

 had, sour small beer, or other similar liquors, may, probably, be 

 used with the same success. The quantity of tin used in tinning a 

 definite number of plates, each of a definite size, is not the same 

 at different manufactories. In some fabrics in Bohemia, they use 

 fourteen pounds weight of tin for making three hundred plates, 

 each of them being eleven and one.third inches long, by eight and 

 a half broad ; according to this account, one pound of tin covers 

 a surface of twenty .eight and one.third square feet: in other, 

 where the tin is laid on thicker, one pound will not cover above 

 twenty. two square feet ; the thickness of the tin, even in this case, 

 is small, not much exceeding the one-thousandth part of an inch -, 

 though that is near twice the thickness which tin has upon copper 

 in the ordinary way of tinning. I have inquired of our English 

 manufacturers concerning the quantity of tin used by them iu co- 

 vering a definite surface of iron ; and from what 1 could collect, it 

 is very nearly the same with that used in Bohemia, from whence 

 we derived the art of tinning, or twenty-eight square feet to a 

 pound of tin. 



There are various tin plate manufactories established of late 



