What is Bronze?
One of the comments that I have commonly heard is goes
something like this, “Wow, I really like this but it is way
too expensive, it costs as much as my car”. How do I
respond? What do I say to this frugal consumer? The first
thing I usually do is to say you are right, bronze is
expensive. The next thing I do, if my audience seems
receptive, is to begin the process of explaining why bronzes
are always priced so high. Let me try to describe this
process here.
The bronze that a consumer sees is the final product of many
separate, expensive and time consuming steps. The first step
is the creation of the original artwork.
The Original Artwork
After coming up with an idea of what I am interested in
doing I make several rough sketches of what I would like the
final product to look like. If my idea involves an actual
living or extinct animal I spend some time here doing
research. When creating the piece Centaur Warrior, I
photographed and video taped horses standing, walking and
running. I researched the anatomy and musculature of a
horse. When creating the Plesiosaur I read and consulted
with leading paleontologist in the field to make sure the
details were as correct as we can make them with the
knowledge we have. I then create a metal armature. The
armature is a framework for the soft clay or wax that I will
layer and sculpt into a finished piece. This is for me one
of the best parts of creating bronze sculptures. The wire
armature lets me create something airy, light and full of
movement and energy. The clay or wax coating lets me add
detail over this light support. Neither product is all that
great in itself but taken together something really neat can
be created. The time for this process varies with the piece
but it is not unusual to spend weeks or even months on an
original sculpture. One problem with this combination of
materials is that it is not permanent, clay pieces are quite
fragile and are easily damaged. Bronze is tough and
extremely durable material, so now to turn the clay piece in
to bronze.
Making Molds and Casts
The clay can not be directly turned into bronze, there are
several intermediate steps, and the first of these steps is
making a mold.
A mold is made of the clay original, usually out of some
type of rubber, which is poured around the original as a
liquid and then allowed to harden. This rubber can be
expensive. A five-gallon bucket may cost around 600.00
dollars. I am constantly amazed at the detail this rubber
can pick up; fine markings on a sculpture down to faint
fingerprints are faithfully reproduced. The trick to this
process is to make a mold that is easy to remove without
destroying your sculpture. Molds can be very simple
one-piece molds of relatively flat two-dimensional surfaces
with little relief. They can also be very complicated
multiple part molds surrounded by multiple part mother
molds. Generally the more complicated the original the more
complicated the mold. My large winged dragon sculpture, Out
of the Blue, required numerous molds totaling about 16
separate pieces, in this sculpture the original actually had
to be cut into smaller pieces and have molds made of these
parts. After the molds have been successfully poured they
are removed from the original and cleaned. They are now
ready to create a wax cast of the original sculpture.
In this step wax is melted and poured in to the molds
prepared earlier. This is an important step; an artist who
invests time and materials into getting a sculpture to this
stage does not want a bad wax cast. Care is taken to ensure
any air bubbles, mold seams or other blemishes on the
surface of the cast are removed. A well-prepared mold helps
but there are always some details that need cleaning up. If
the mold had many parts this is one stage in which many of
these are reassembled.
Now, off to the
foundry.
All true cast bronze is still created using some variation
of the traditional technique of lost wax casting. In this
process the wax cast is encased in ceramic shell. Dipping
the wax into a resin compound and then into fine sand
letting it dry and then repeating the process many times
creates the ceramic shell. When completely dry this is put
into a kiln and baked to melt and drive out the wax. This
leaves a hollow shell with a cavity inside that looks
exactly like the original clay. Wax pieces had been added
prior to creating the ceramic shell, which when melted away
leave a hole in the shell for molten bronze to be poured in
and air to come out. The bronze is melted from ingots at
more than 2000 degrees Fahrenheit. When the crucible
containing this bronze is taken out of the furnace it glows
like the sun. It is very impressive! The molten bronze is
poured into the shell filling up the smallest cavities. At
these temperatures it flows like water.
Cleanup and Chasing
After the bronze has been allowed to cool, on a big piece
something that may take a day, the ceramic shell is broken
off of the cast bronze. It pretty much just shatters when
lightly struck. The bronze right out of the shell is not a
pretty site. It has to be cleaned and chased to remove any
imperfection. If the sculpture was not cast in all one piece
the separate parts are now welded together with additional
attention being paid to chase and clean up the weld joints.
It still does not look like a finished piece but it has come
a long way. It is now sand blasted to remove any remaining
shell or chemical residue from the casting process.
Patina
All bronzes must have some type of finish. The finish can be
applied at the foundry or can slowly form over the surface
of the bronze. This finish is called the patina. Patinas
vary widely in color from black to blue to green to red to
brown to white. What all patinas have in common is that they
are chemically a part of the sculpture’s surface, they are
never a painted coating. Patinas are often applied hot. To
do this the bronze is heated back up to about 400-500
degrees Fahrenheit and various chemical solutions sprayed or
brushed on. These react with the bronze to form the durable
patina.
Mounting
The bronze is now almost done. The final step is to mount
the sculpture on some type of complimentary base. Mounting
material can be some type of stone such as marble or
granite; it may also be a fine wood like cherry, walnut,
maple or oak. Bases are often a combination of material
chosen to display and accentuate the sculpture.
Durability
True bronzes are made of tough durable pure metal. There are
cheaper versions of bronze sculpture. Some of these go by
name cold cast bronze. This is nothing more than bronze
powder mixed with a resin. They often have a piece of metal
inside to give them the heavy feel of real bronze. When
dropped they are easily marred in a fire they would burn or
melt. They are not true bronzes. A true bronze sculpture
will virtually last forever. Bronzes have been recovered
intact from ship wrecks and the buried ruins of ancient
civilizations. True bronzes weather raging fires and might
need nothing more than a little sandblasting and patina to
be as good as new. A cast bronze will last for thousands of
years. A beautiful bronze sculpture can add excitement and
joy for generations.
Limited Additions and Cost
Creating bronze sculpture is very expensive. Foundry charges
alone can be more than half the value of a finished artwork.
This does not even include the initial investment by the
artist in both time and materials. Much of an artist expense
goes into many of the steps before the artwork ever makes it
to the foundry. Making copies can spread this cost out. Most
of the bronzes sold are limited editions. This means that
the artist decides ahead of time how many copies he or she
is going to make. An open addition means that the artist
reserves the right to make as many copies as he wants.
Generally the more copies made the less expensive an artwork
might be while the fewer copies the greater the expense to
the consumer. In my descriptions of my sculpture I always
list whether or not the sculpture is open or not and if
limited how many I plan on making. The molds will be
destroyed when the last cast has been made. The number of
the addition is on each piece.
Pick out a sculpture, take it home and enjoy!
