Before soldering, the surfaces must be quite bright and close
together; and the contact of air must be excluded during the operation,
else the heat will tarnish the surface and prevent the adhesion of the
solder: the borax and resin commonly in use, effect this. The best plan
is to clean the surfaces with muriatic acid saturated with tin: this
method is invariably adopted by watchmakers and opticians, who never use
borax and resin. The point of the soldering-tool must be filed bright.
Copper, to tin.--Clean the copper well with sandstone; heat it, and rub
it with sal-ammoniac till it is quite clean and bright; the tin, with
some powdered resin, is now placed on the copper, which is made so hot as
to melt the tin, and allow it to be spread over the surface with a bit of
rag. A very little tin is used in this way: it is said that a piece as
big as a pea, would tin a large saucepan; which is at the rate of twenty
grains of tin to a square foot of copper.
LEATHER.
Raw Hides.--Dressing Hides.--Skins that have been dressed are essential
to a traveller in an uncivilised country, for they make his
packing-straps, his bags, his clothes, shoes, nails, and string,
therefore no hide should be wasted. There is no clever secret in dressing
skins: it is hard work that they want, either continual crumpling and
stretching with the hands, or working and trampling with the feet.
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