1,000 years later in the sixteenth century BC, Egyptian
foundry can be compared to and contrasted with the
Greek foundry scene shown on the sixth century BC. Again
there is a furnace with two men tending it.  This furnace
also has a crucible sitting on its top.  Behind the furnaces
care skin bellows.  To remove the crucible from the
furnace, the bronze workers stood on a ramp and attached
a of tong arrangement to the crucible to lift it onto their
shoulders and transport it to the level of a casting pit.
Egyptian Foundries
An Egyptian tomb painting from about 1,500
BC depicts a scene of a foundry and bronze
doors being cast. In the scene several
important parts of the actual casting process
are revealed and crucibles probably full of
metal ore being smelted over a bowl
furnace. Instead of blowpipes, the blast-air is
created by the use of drum bellows.  The
dish bellows are being moved with a pair of
strings. The smelters are standing on the
twin bellows and holding the strings . As they
rock back and forth, they press one set of
bellows with their heels and raise the skin of
the other with the string to draw
fresh air inside. The pipes on the bellows
are inserted into funnel-shaped nozzles
called tuyeres ("twee-yer") made of baked
clay. Tuyeres are an essential part of a
bellows, and they have been found near
ancient smelting furnaces or on smelting
sites in various areas. Two more workers
lift a lipped crucible full of molten metal
from the furnace using two crossed sticks
as a type of tongs. Next, a pair of workers
is pours molten bronze from a crucible
into a series of cups leading into  large
clay mold.
BRONZE FOUNDRIES IN ANCIENT TIMES
Around 3,000 BC, Mesopotamia metallurgists discovered that
adding a small amount of tin ore to copper during smelting
produced a harder more useful and stronger metal.  They
had created bronze. The addition of tin lowered the
temperature required to melt copper and bronze was more
fluid and easier to cast. The first examples of bronze  have
been found in the tombs of Sumerian kings- the rulers of the
lower Mesopotamian Valley.  Through trade in the eastern
Mediterranean, bronze technology made its way into Egypt.  
The Egyptians were using it in a small way by around 1,500
BC.   Bronze was not in common use in Egypt until about
1,000 BC.
way that are today.  Once cast is cooled and removed
from the molds, the sections of the large statues were
joined together and finished. Analyses done on bronzes
in the Harvard Art Museums exhibit, reveal that often the
pieces were joined by a process called flow welding in
which molten bronze  was poured between two pieces.
The pieces often were joined with lead solder requiring
lower temperatures.

Flaws on castings were  repaired with rectangular
patches and the holes left by chaplets were patched with
bronze or left open if  not easily visible. Often the eyes
of the statues were made of glass and inserted from the
outside, attached to the sockets with a resinous fixative.
Copper lips and silver fingernails were often added. The
classical bronze statues that survive today are often
missing these finishing touches.

These indirect castings made by Greeks and Romans
stand in  evidence of the high level of sophistication of
the bronze-casting technology that they employed.
Roman Bronze
Greek Bronze
Mesopotamian Sculpture
Egyptian Bronze
Sumerian Vase
is not at the correct
temperature and fluidity, the
casting will fail and crack or
result in a deformed shape as
it cools.  Ancient craftsmen
realized these limitations.  
Lead was added to a
copper-tin bronze to lower the
melting point and make the
molten metal less viscous to
pour more easily.   Once in
their clay
casting sections were lowered into in casting pits like
those found on the Agora at Athens. Molds were 'fired
out' to expel the wax and harden the clay.  The molds
were surrounded with a packing of sand or dirt for
support  and then cast  with bronze from the same
batch.  The crucible furnace was placed on the edge of
the casting pit.   "Canali" or channels lead from the
furnace and the bronze would flow by gravity into the
openings of the mold.
Greek and Roman foundry
workers never used such a
furnace and crucibles were used
in the same way that are today.  
Once cast is cooled and
removed from the molds, the
sections of the large statues
were joined together and Greek
and Roman foundry workers
never used such a furnace and
crucibles were used in the same
Mesopotamian Coins
Wax Casting
By the sixth century BC,  bronze-casting was very
sophisticated, and. Initially, small bronze objects and
tools were solid cast in two-piece clay molds. From
1,500 BC onward, larger items were being
hollow-cast  using the lost-wax method. A clay core
was formed in the basic shape of an object and then
covered with wax and the details of the statue  were
molded. Wax sprues and gates  provided pathways
for the wax to evacuate the mold and for the molten
metal to enter. Vents were also added through for the
hot gases to rise while the liquid bronze was being
poured. The wax model was painted with very thin
clay  to pick up the finely sculpted details. It was
coated completely with a coarser clay. This was
attached to the core by bronze pins called chaplets.
The clay mold was heated slowly so the wax would
melt out and then fired at a higher temperature to
harden. The empty space left by the wax was filed with
molten bronze. The bronze was then cooled for a one
or two of days and the clay mantle was broken
revealing bronze object.  The chaplets, vents, and
gates were removed and the  statue was finished by
cold-working techniques. The limitation of this method
was that the mold can only be used a single time.

Most of the large-scale bronze statues produced by
the Greeks and Romans were made in the indirect
method of hollow-casting.   The clay core is finished
more completely and a cast is taken,  This became a
master mold which was dried, and wax was painted
into the negative impression.

The benefit of this extra step is that the master mold
can be used multiple times. Large-scale statues made
by the Greeks and Romans were often cast in a
series using a master mold . The Riace Bronzes,
discovered underwater by divers in 1972  near
Reggio Calabria, are an example of serial production.
These large statues have similar body styles but
different details. They were probably made from the
same master mold but cast at different times.

Large Bronze Statues Cast
by the Greeks & Romans
Large-scale bronze statues were usually cast in
sections  of about 3 feet. The most two men could
handle was a crucible holding about no more than 2
gallons of molten bronze weighing 150 lb. Bronze
must be poured fairly rapidly because when it will
begins to cool it will not pour uniformly. If the bronze
Demo One The History of
Casting Bronze
Greek Foundries
Ancient Roman
Bronze Shield
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