Brass . 
115 
The following process for tinning is attended with no 
danger from poisonous ingredients, as no lead is used in 
it ; the tinning, too, is exceedingly durable, adds strength 
to the copper vessel, and secures it from the action of acids 
much longer than the common tinning When the ves- 
sel has been prepared and cleaned in the usual manner^ 
it must be roughened on the inside by being beat on a 
rough anvil, in order that the tinning may hold better, and 
be more intimately connected with the copper. The pro- 
cess of tinning must then be begun with perfectly pure 
grained tin, having an addition of sal ammoniac instead 
of the common colophoniunx.% Over this tinning, which 
must cover the copper in an even and uniform manner 
throughout, a second harder coat must be applied, as the 
first forms only a kind of medium for connecting the se- 
cond with the copper. For this second tinning you em- 
ploy pure grained tin mixed with zincf in the proportion 
of two to three, which must be applied also with sal am- 
moniac smooth and even, so that the lower stratum may 
be entirely covered with it. 
This coating, which, by the addition of the zinc, be- 
comes pretty hard and solid, is then to be hammered with 
a smoothing-hammer, after it has been properly rubbed 
and scowered with chalk and water, by which means it, 
becomes more solid, and acquires a smooth compact sur- 
face. 
Vessels and utensils may be tinned in this manner oa 
both sides* „ In this case, after being exposed to a suffi- 
cient heat, they must be dipped in the fluid tin, by which 
means both sides will he tinned at the same time. 
As this tinning is exceedingly durable, and has a beau- 
tiful colour, which it always retains^ it may be employed 
for various kinds of metal instruments and vessels which 
it may be necessary to secure from rust. 
2 Rosin. f See the next paper* 
