Ancient Bronze Foundries

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