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BOOK IX
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Nature
may tint metals with a color that is foreign to them. The true color of
copper is red yet sometimes it occurs yellow. The Greeks call this όρβίχαλκος. Sometimes copper is white and this is called \f/ev8apyvpos. The
latter has the appearance of silver, the former the appearance of gold.
Pliny writes that the yellow copper has a characteristic and pleasing
beauty by day. Strabo writes that the white copper was made in
Teu-thrania near Andera and in Lydia near Mt. Tmolus. Copper can be
colored artificially to imitate nature.
Native cadmia1 is added to copper to make brass (orichalcum). According
to Pliny at one time Livian copper was used chiefly in making brass and
later, Marian copper. Brass is made in the following way. Alternate
layers of the best broken copper and cadmia are placed in a
tall crucible. When it is full it is lowered into a furnace in a space
that has been hollowed out and is fired as if it were in a covered
passage. When entirely melted, the copper is changed into brass with
the color of gold. This is the common method. By another method sheets
of copper three-quarters of an inch wide are placed in a crucible
similar to those used in casting silver but having the outside covered
with a clay containing iron scale and the inside covered with the most
highly refined honey. The thin sheets of copper are also coated with
honey. They then sprinkle over the copper a very fine powder consisting
of native calamine, dry dregs of wine that they call tartar (argol) and
charcoal in equal amounts. The crucible is covered with an earthenware
lid with a hole in it. A rod is thrust through this hole and used to
stir the molten copper. The lid is sealed to the crucible with the
above mentioned clay. The crucible is then placed in a furnace similar
to those used in a mint. When the calamine mixes with the copper it
first gives off a red flame, then a flame that is part red, part blue
and finally a yellow flame that indicates the mixing is completed. Then
the crucible is removed from the furnace.
They
make many things from brass but most commonly basins, candelabra,
lichnuches, and siphons. These articles are more valuable when made
from brass than from copper since they have the same hardness and a
more pleasing golden color. Brass, like copper, can be whitened with
powdered gypsum that occurs in crusts until it has the
appearance of silver. Copper so whitened is pleasing and esteemed and
for that reason is made into goblets. Copper is also whitened in the
following manner.
1
The literal translation is calamine. This name is given in the United
States to the natural hydrous zinc silicate and in England and Europe
to the natural zinc carbonate. To eliminate this confusion it has been
proposed to use the name calamine for oxide zinc ores in general and
call the carbonate smithsonite, the silicate hemimorphite. Under cadmia Agricola included not only the natural zinc oxide minerals but also artificial oxides.
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187
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