- [Voiceover] This sculpture, the Juggling Man,
by the Dutch artist Adriaen de Vries,
was made around 1615.
To create it, de Vries used a process called
the direct lost-wax method of casting.
This method is composed of three steps:
modeling, casting, and chasing.
Bronzes made by this method
are cast from the original model,
which is made of a wax skin over a clay core.
In this process, the wax skin is melted away
resulting in a unique,
one-of-a-kind bronze sculpture.
If the cast fails, the sculptor must begin again.
X-rays of the Juggling Man
gave conservators vital clues
in reconstructing de Vries's modeling
and casting techniques.
X-rays show that a heavy iron armature
or internal frame remains inside the bronze.
This is a feature used only
in the direct lost-wax method of casting.
As seen in this modern recreation
of de Vries's process, making the armature
requires blacksmithing skills
to heat and hammer the heavy iron
into the desired shape.
The sculptor determines the placement
of the figure's arms by bending the rods.
He then ties the iron rods together using wire.
The artist continues to adjust the composition
securing the rods together
until he is satisfied with the basic form.
Once complete, this sturdy armature
provides the underlying support
for the artist to construct
the basic form in clay.
Wet clay is applied to the armature
to build the form in a process called modeling.
The artist continues adding clay
and smoothing the surface
until his form is complete.
This clay model is called the core.
You'll notice that there is no clay core
where the figure's hands should be.
X-rays showed that the carefully detailed hands
did not contain a clay core
but were modeled in solid wax.
When finished with the modeling,
the clay form is fired to strengthen it
and to eliminate all moisture.
After the form is fired,
a layer of wax skin is applied to the clay core.
De Vries probably would have used beeswax
with resin and colorants
because details cannot be seen
in natural pale yellow beeswax.
The artist then refines the wax form,
smoothing the surface and sharpening the details.
Next, the artist makes short iron pins
called core pins that will hold the clay core in place
when the wax skin melts away.
With a hammer and chisel,
the artist cuts these pins into small lengths.
Using a tool called an awl,
the artist makes holes through the wax
and into the clay core to accommodate the core pins.
Finally, the artist carefully inserts
the core pins through the wax and into the core.
In the next step, the artist attaches to the model
a network of wax rods called sprues.
He uses hot metal tools as well as his hands.
To further secure the sprues,
the artist carefully adds a wax reinforcement.
These sprues are connected to a wax pouring cup at the top.
The model is now fully encassed
in its network of sprues.
With a brush, the artist applies to the model
a mixture of clay and other materials
that can withstand high temperatures
and absorb gasses.
This outer mold is called the investment.
Using his hands, the artist builds up the investment
until the model is completely embedded in a solid mass.
This cross-section of the solid investment
reveals the investment's various layers:
The armature,
the inner clay core,
the modeled wax layer,
the core pins,
the network of sprues,
and the pouring cup.
The investment is turned upside down,
placed in an oven called a kiln, and heated.
The next step takes place inside the investment
and cannot be seen.
The wax layer surrounding the clay core
melts out, creating a space for the molten bronze
that will become the final sculpture.
The melted wax sprues are now hollow channels
that will bring the liquid bronze
into the outer mold
and carry escaping gasses away.
After the wax has melted out,
the investment is buried in a sand pit.
This protects the foundry workers
because if improperly prepared,
the investment could explode
when the hot, molten bronze is poured.
The pour happens during the next
and most dangerous step of the process,
the casting.
All of the steps up to this point
have been in preparation for the actual
casting of the sculpture in bronze.
This takes place in a hot,
noisy, and dangerous workshop called a foundry.
It is here that the bronze metal is melted
at about 2,000 degrees Fahrenheit,
within a container called a crucible
which is placed inside the furnace.
Foundry workers called founders open the crucible.
They scrape off the waste products
that gather at the top of the molten metal
and dump them into the furnace pit.
Next, the founders secure the carrying arm
around the crucible so that it can be
removed from the furnace.
The crucible is clamped into a pouring ring
so that it won't tumble into the mold during the pour.
Watch the hand of the man on the right
as he secures the clamp.
The heat is so intense
that his protective glove momentarily catches fire.
Molten bronze is poured into the buried investment
filling the space left by the melted wax.
The investment is allowed to cool
and the metal hardens.
In a dramatic moment,
the artist knocks away the investment
to reveal the freshly cast sculpture within.
Now the most labor intensive part of the process begins.
Once the bronze is freed from the investment,
the artist has to clean it up
in a process called chasing.
The bronze bears little resemblance
to the final polished sculpture.
Using a chisel, the artist removes the sprues
which are now bronze.
He also pulls out the iron core pins.
Next, the dark, sooty oxide layer
covering the sculpture surface is rubbed off.
The artist repairs flaws
and patches the core pin holes
using plugs made of discarded bronze from the sprues.
Next, he sharpens details in the face,
hair, and finger and toenails
using small, specially shaped iron tools.
The artist then gives the surface
a smooth reflective shine
by polishing it with a cloth dusted with light abrasives.
The finished sculpture preserves
every detail of the artist's original
clay and wax model in bronze,
a material that is both permanent and precious.
Once the bronze is polished, the artist chooses
from a wide range of patinas or surface finishes
which protect the surface and vary its appearance.
A patina can increase luster,
change the color, or hide casting imperfections.
Shown here are several examples
of the types of patinas used in de Vries's time.
De Vries's original patina is gone.
The Juggling Man stood for more
than 50 years in an outside garden.
Weathering and oxidation
caused its uneven green coloration.
Like de Vries, other artists used
the direct lost-wax casting method
to create works such as this sphinx made in the 1500s.
By using this technique,
de Vries ensured that each bronze sculpture
he created was a unique cast.
His commitment to the direct lost-wax method
shows his exceptional skill and confidence
in overcoming its great risks and difficulties.