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Contrary
to the familiar image of Greek sculpture as white marble statues, about
half of all sculpture produced during antiquity was composed of bronze.
The metal is a relatively strong alloy of two other metals, tin and copper.
Bronze was also first and foremost the medium of ancient weapons used by
the Greeks and most other cultures of their time. The metals characteristics
of durability and strength coupled with a somewhat simple method of forging,
made it superior for battle compared to the possible alternatives of stone,
wood, tin, copper, or lead weapons. These facts made bronze a valuable
metal needed by leaders and city states to create armies. None-the-less,
bronze had many other facets of use to which it was applied. But
whenever there was a war, the subsequent need for bronze caused anything,
include the art of statues, made of the metal to be melted down into swords,
shields, spears, and other weapons of war. The lack of modern
bronze statues today is the result of this past wartime meltdown process.
As a medium, bronze proved more versatile than marble and actually contributed
to the transition of Greek sculpture into the Classical Period. The
ability of bronze to hold its shape - no matter how complex - allowed sculptors
to more easily experiment with less rigid poses. During the Archaic
period, sculpture was restricted to the Eastern influenced stringency of
pose, seen in the kore and kouros figures, partly by the
tendency for their medium of either marble or terra cotta clay to crack
if say an arm was extended or fall over if the body was turned in some
angle. Not only was bronze a stronger lighter and medium, but leaden
weights could easily be placed inside the hollow feet, enabling any number
of sculptural poses that would otherwise cause the sculpture to topple
over (or crack from internal stress if the statue was bolted to a base)
if it was made of marble. The construction of life sized bronze statues
involved many complications and required a special technique that took
generations to develop. Creating solid bronzes that are life size
required immense quantities of the valuable metal which distorted if dried
as a large thick mass, so the trick was casting hollow sculptures.
This type of casting was first mastered in ancient Mesopotamia, but around
550 BCE, it is believed that the Greeks developed the technique independently
or that they may have possibly acquired it from the Egyptians at that time. |
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Bronze, the Method of
Sculpting: |
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To
understand the process of sculpting in bronze it aids us to look at the
how the Greek method evolved. In the eighth century (900 BCE), before hollow
casting in bronze was understood by the ancient sculptors, smaller solid
statuettes had been made. These statuettes, typically handheld personal
works, had been carved out of stone thousands of years prior to the eighth
century BCE and their bronze construction was no great innovation, but
it does signify a step along the path towards hollow casting. Larger,
monumental sculpture in stone had been accomplished by the eighth century
and it was only a matter of time before monumental sculpture in bronze
would appear. The easiest method to create hollow bronze sculpture
is not to cast them in one piece, but several, say seven or so. At
first, these pieces were simply sheets of bronze hammered, as bronze is
rather malleable or re-formable by smooching and flattening, and then welded
together to create a closed hollow sculpture sometimes having a wooden
frame. The technique the Greek sculptors used after 550 BCE to cast
full size bronze sculptures is a bit more complex, for it does not rely
on the welding of metal sheets but the on the making
of a single piece formed directly from a mold. |
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Beginning
with a clay or plaster full size model replete with all the details of
the final work, a mold would be created. The model, as it was made
of a weaker material than either marble or bronze, was often made by covering
a wooden frame, with head, arms, body, and legs, with a few layers of clay.
The mold is created by covering the clay original with a half inch thick
layer of wax and then a much thinker layer of clay. Before the mold
(the mold consists of the outer covering of clay) has dried, several large
nails were inserted though the clay and wax and tightly fit into the inner
clay model. The reason for the nails is they act to brace the model
in place, so it does not move once the wax in melted away (exiting though
a small hole or two drilled in the mold but latter filled back up with
clay), as is done when the entire mold and model are heated in the next
step. |
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At
this point, with the wax gone (a step where the clay mold and clay model
hardened from the firing) and with the supporting function of the nails,
there would exist a half inch thick air space, between the mold and model.
This space is then filled with molten bronze poured down in a small hole
or two in the mold. When the bronze has solidified and cooled, the
clay mold is removed, revealing a hollow bronze statue. Well, it
is not really hollow since the clay model has yet to be removed, but this
is easily performed by scraping out the model from a small opening on the
bottom. That entire process provided the easiest method to
produce hollow bronze sculptures, but whether it or another, similar though
more complicated, method was used by the first Greek casters cannot be
determined. The other method relied on a mold and a core (in the
last method the model served as the core, but the core in this method is
not the original model) but the major difference is instead of the mold
being one piece it is made out of several. The first step of this
process is the creation of these mold pieces. Exactly the same steps are
followed as before in covering the clay model with wax and clay, but now
the mold is removed (without melting away the wax, for this time the wax
merely acted to prevent the clay from adhering to the model) in pieces:
like one piece for the chest one for the back, two for the sides, and so
on. The sculptor also had the option of applying the clay (composing
the mold) directly onto the clay model (without the wax); this captured
all the details of the original model but it involved shaving half an inch
off the mold such that bronze could later fill this created space between
the mold and core. Adding another twist to this method, all the pieces
of the mold would be reconstructed, this time without the model inside,
in effect making a hollow clay mold. Next, an adhesive material would
be poured inside filling the hollow mold, and after the material dried
into a solid form, all the pieces would once again be removed. The
result of these steps is the creation of a core, which is essentially a
carbon copy of the original clay model. This is actually an important
step that makes this method revolutionary as it preserves the original
model allowing the sculptors assistants to
reproduce the same sculpture
any number of times by simply taking more mold pieces from the model and
then making additional core pieces. The wax is then removed from
the mold pieces and the fine details of the final sculpture are easily
carved into the soft clay interior of the mold parts. The details
are carved into the inside of the mold because that surface will eventually
be in contact will the molten bronze. Wax is then put back into the
interior of the mold pieces over the details just added. After the
core is complete and the mold finished and re-waxed this method actually
branches with two different choices to move on from. The limitations
of working with molten bronze encountered by the first casters probably
made the choice of casting seven or so pieces from the various mold pieces
and the core. This choice is easier to implement as each bronze piece
cast dealt with a small portion of the entire sculpture like a leg or head,
for example (again nails would support the mold over the core and the wax
would be melted away prior to addition of the liquid metal). Once
enough smaller bronze pieces were cast they would all be welded together
into the form of the finished sculpture, just like the hammered bronze
sheets were connected by the more primitive sculptors. The other
choice, requisite of a higher degree of experience in working with larger
quantities of molten bronze, was the casting of one single bronze piece.
This choice involved a complete reconstruction of the mold over the core,
the insertion of supportive nails, the draining of the waxen inner lining,
and then the filling of the empty space (left behind when the wax melted
away) with molten metal. The name for these methods of casting bronze
sculpture is cire perdue, translated quite fittingly to "lost wax"
as wax is drained from the mold and "lost" in that sense. |
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| Riace
Bronze: Warrior Figure. |
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Any
sculpture created from any of the previous casting techniques still needed
some finishing touches after it was removed from the mold and after the
core inside was scrapped out, before it was considered complete.
First, the metal had to smoothed and polished and some details like hair
were carved into the metal. A varnish was then applied to change
the yellow color of the bronze to a darker or lighter hue, as was desired
by the sculptor. Another finishing step was the addition of other
metals, such as copper nipples and silver or gold for the lips and jewelry.
Enamel or glass was often inset in the eyes to give them a realistic appearance
and fine strands of copper were sometimes used as eyelashes and eyebrows.
Unlike marble, the nature of bronze permitted the sculptor to utilize exquisite
detail and extraordinary shine or dullness; in other words: although bronze
was more costly, it was a versatile and powerful medium for the art of
sculpture. The other bonus of sculpting in bronze was the ease of
transportation, considering how light a hollow bronze statue is compared
to a counterpart in marble. Indirectly, this transportation of bronze
statues-- primarily those shipped by boat - has helped build our supply
of Greek original bronze sculpture. The not too uncommon storms that
arise out of nowhere in the Mediterranean occasionally would sink trading
vessels and with them their cargo of bronze statues that would all be covered
with the thick mud at the sea floor. Although the covering mud makes
the discovery of these sunken statues more difficult, it acts to preserve
the metal that would otherwise corrode away. One such discovery has
provided the Riace Bronzes, two key transitional sculptures into
the Classical period, belonging specifically to the period, around 450
BCE, known as the Severe style.
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