This is prepared by dissolving filings or slips of copper with
nitrous acid in a receiver. When the acid is saturated, the slips
are to be removed; or, if filings be employed, the solution is to be
poured off from what remains undissolved; small bars are then put
in, which will precipitate the copper from the saturated acid, in
a powder of the peculiar appearance and colour of copper, and the
liquid being poured from the powder, this is to be washed clean of
the crystals by repeated levigations.


177. COMMON SIZE

The size used by painters for most sorts of common work is prepared
by boiling in water pieces of parchment, and of the skins of
animals and fins of fish, and evaporating the solution to a proper
consistency. It only differs, however, from a solution of glue
containing fewer foreign ingredients, and in not being so strong.


178. DR. JOHN'S VARNISH FOR PLASTER OF PARIS CASTS

Take of white soap and white wax, each half an ounce, of water two
pints; boil them together for a short time in a clean vessel. This
varnish is to be applied when cold, by means of a soft brush. It
does not sink in, it readily dries, and its effect may be heightened
by lightly using a silk pocket handkerchief.


179. GENERAL DIRECTIONS FOR BRONZING