Main content
Course: Special topics in art history > Unit 2
Lesson 8: Sculpture- Working jade
- Quarrying and carving marble
- Carving marble with traditional tools
- Casting bronze: lost-wax method
- Casting bronze: direct lost-wax casting
- Making a Spanish polychrome sculpture
- Making a Spanish polychrome sculpture: Saint Ginés de la Jara
- After the Fall: The Conservation of Tullio Lombardo's "Adam"
- Object Conservation - Salisbury Cross
- Contemporary Art Conservation at Smithsonian's Hirshhorn Museum
- Conservation: Cast of the Pórtico de la Gloria
- Conservation: The Nasrid plasterwork collection at the V&A
- Conservation: Playing Tipu’s Tiger
- Conservation: The Wolsey Angels
© 2024 Khan AcademyTerms of usePrivacy PolicyCookie Notice
Casting bronze: direct lost-wax casting
The Dutch artist Adriaen de Vries created the unique bronze sculpture, the Juggling Man, using the direct lost-wax method. This intricate process involves modeling, casting, and chasing, with each bronze cast being one-of-a-kind. X-rays reveal the heavy iron armature within, a signature of de Vries's technique. Created by Getty Museum.
Want to join the conversation?
- What do the terms "direct" loss and "indirect" loss refer to?
I understand the individual methods, but where and how did these terms come into effect?(19 votes)- By heating the crucible the bronze is melted, going from a solid state to a liquid state which would then be capable of being poured into the waiting mold.(1 vote)
- What happens to the clay? I am assuming that since the wax melts away, the clay remains inside; attached to the internal frame. Is this correct or is there a way to remove it?(6 votes)
- The base clay stays in the unless the artist removes it, which could damge his work.(11 votes)
- why can't the whole sculpture be made out of bronze--why do you need a clay core?(3 votes)
- A sculpture that was pure bronze would be possible I think,but it would be very expensive and very heavy too,.(5 votes)
- Why the oven called a kiln? Is there any root word in it?(3 votes)
- The word kiln descends from the Old English cylene (/ˈkylene/, which was adapted from the Latin culīna 'kitchen, cooking-stove, burning-place. During the Middle English Period, the "n" was not pronounced, as evidenced by kiln having frequently been spelled without the "n", Another word, "miln", a place where wheat is ground, also had a silent "n". Whereas the spelling of "miln" was changed to "mill" to match its pronunciation, "kiln" maintained its spelling, which most likely led to a common mispronunciation, which has now become commonly used. However, there are small bastions where the original pronunciation has endured. Kiln, Mississippi, a small town known for its wood drying kilns that once served the timber industry, is still referred to as "the Kill" by locals.(3 votes)
- What is a crucible made out of that it can hold that hot of materials and keep its shape?(2 votes)
- In this time period very good crucibles were made in Germany of a white clay "kaolin".
Some of these were known as "Hessian Crucibles".
The Aluminum and silica of the kaolin form refractory crystals "Mullite" when fired, this produces a strong and heat resistant crucible.
In the USA kaolin is mined in Georgia.
https://www.sciencedaily.com/releases/2006/11/061123120134.htm(2 votes)
- This is one of the best videos in this section of mataerial. Good detailed information. Previous videos were too short....(2 votes)
- Could you please comment how the big bronze sculptures or the huge bronze church bells are casted? Is the technology the same? I mean all large statues that we see in cities now have iron armature and clay core inside; and were made using wax skin and investment as described? Thank you very much(2 votes)
- How long and difficult would it be for the artist to make this flabbergasting statue?(2 votes)
- so why would someone want to go through all that work for a sculpture?(0 votes)
- To create something permanent. Or, perhaps, because they enjoy it. Or maybe just for the incredible amounts of money that can be earned selling skillful sculptures, particularly metal ones. It's hard to tell the motives of any given artist.(3 votes)
- can you reuse the wax after it is used?(1 vote)
- The wax largely burns off so I don't think you could recover enough to be useful.(2 votes)
Video transcript
- [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.