Sculptors have long revered Bronze for its vast versatility. As bronze remains one of the few materials capable of retaining intricate detail over time, it is an exceptional choice.
An original bronze sculpture is created using the Lost Wax technique to mold a wax model into a ceramic shell. After baking, wax melts away, leaving an opening into which molten bronze flows freely.
Metals
Bronze alloy comprises copper, tin, and zinc bonded together by alloy. Copper gives bronze malleability and ductility, while the container and zinc combine to strengthen the final product. Bronze’s power allows it to keep fine details intact for generations – even under outdoor conditions!
Starting a bronze statue project begins with modeling it in clay, an ideal material for capturing minute details and making design modifications as it develops. Sculpting in clay also allows artists to adjust as their project advances quickly.
Once a sculptor is satisfied with their design, they will use silicone rubber molds to cast their piece. This serves as the master mold from which all castings will be created – for complex sculptures; this may involve multiple steps that join together and is known as negative casting.
After baking the ceramic shell, its wax model will have “dissolved,” hence “lost wax casting.” Once this stage has been completed, molten bronze (at 1200degC) is added and allowed to cool before the ceramic shell is taken off to reveal the bronze casting; this is known as breaking out and can require using a sledgehammer. Any remaining sprues must then be cut away before inspecting for flaws in their form.
Bronze remains one of the premier choices for monumental statues, being both lightweight and highly durable. Bronze can be used outdoors and indoors – an advantage not often associated with more fragile materials like marble.
The bronze sculpture is highly adaptable and flexible, enabling sculptors to work with it to craft intricate designs impossible with other mediums like stone or wood. Bronze allows a sculptor to add intricate details not possible with other media like stone or wood while incorporating other materials such as glass or granite into his or her statue for depth and dimension. Once complete, bronze statues can be mounted onto bases that complement them – such as granite pedestals for statues of people, while tree stumps or pieces of wood may work for animal sculptures.
Casting
Foundries specialize in turning sculptures from their original medium into bronze using the “Cire Perdue” or ‘Lost Wax” method that dates back thousands of years – an exact craft.
Start by cutting apart an artist’s original sculpture into multiple sections (torso, arms, etc.) and covering each with rubber to produce an exact wax duplicate. A plaster mother mold is then built around this to add rigidity. Finally, the rubber coating is carefully removed, leaving behind an empty ceramic mold – this becomes your first negative.
Once the ceramic shell covering the wax has set, it is inverted, and the molten bronze is poured in, creating a second negative. The ceramic shell can be removed after it has been developed and cooled sufficiently.
If the original sculpture included an internal frame or armature, this would now be constructed of heavy iron rods by a blacksmith who then hammers and bends them into position before tying them together using wire to give shape to it. This step is especially crucial when working on larger pieces, as, without this support, the bronze would crack and disintegrate into dust.
Wax Chasing” follows. At this stage, an artisan carefully rejoins all of the pieces from the upbeat wax version of the sculpture, eliminating seams and filling any imperfections with heated customized soldering irons or tools (dental tools are ideal). At this stage, it is imperative that the artist personally inspects their work to approve before signing it off as completed.
The foundry also adds solid wax rods, known as sprues, which act as channels for the molten bronze to enter and exit. At this stage, smaller wax bars, or vents, are added as vents to release air during firing to ensure no trapped air remains trapped within the finished bronze statue. All this process must be executed with great care and precision as this step is both time-consuming and labor-intensive; once completed, it can be assembled.
Patination
Bronze has long captured the hearts and imagination of civilizations across time, offering glimpses of eternity through its timeless beauty. Over its long history, various techniques have been used in casting bronze sculptures; However, their specific use may differ slightly. Nonetheless, basic principles remain constant, and it is ultimately up to each artist’s skill and vision that creates unique pieces that stand the test of time.
The conversion of sculptures from their original mediums into bronze begins with a rubber mold. Half of the statue is nestled into soft clay. In contrast, half is painted evenly with viscous rubber paint (polyurethane for small editions, silicon for large or multiple), then when dry, a rock-hard mother mold made of plaster is constructed around it.
Once a plaster mold has been constructed, the sculpture’s wax “positive” is created by carving from rubber positive. Once complete, this cheerful wax sculpture will undergo “slushing,” where more excellent resin is used each time to avoid melting away previous layers. After applying three coatings successfully, investment can occur where channels are added into its wax version so molten bronze may travel.
Based on the size and finish of your sculpture, bronze casting can be done in one piece or in multiple parts to be later assembled. This process may take up to one week; once cooled off, the cast bronze must be cleaned of any developed metal sprues, oxides, or oils.
Now the bronze can be colored using patination, an intricate chemical process that produces various hues ranging from the dark brown of antiques to green, blue, and even purple hues. Patinas can be applied directly onto polished bronzes or left unpolished for use later. Historically, ancient Asians buried their bronzes underground to oxidize naturally over time. Modern foundries use chemical mixtures of oxides and nitrate with heat to do this more quickly.
Finishing
Bronze is an inspiring material, captivating both artists and art enthusiasts. With its aura of wealth and nobility, bronze statues have long been used by gods and monarchs in history to represent themselves and power. So how is this ancient medium made? Below is the journey a bronze statue takes from conception to completion.
Large-scale sculptures begin life as clay, plaster, or wax models. When creating giant sculptures using this direct method (pictured above), an indirect hollow lost-wax casting technique may be utilized; otherwise, for smaller-scale models, indirect open lost-wax casting may be more appropriate. Once complete, models are coated with an investment layer consisting of plaster mixed with sand and water that hardens into an inorganic shell over the wax layer, later serving as molds to receive liquid bronze when it melts away from their molds after the wax is melted away – this shell becomes the molds into which liquid bronze will then flow.
Once the wax casting process is complete, it must be assembled back into an exact positive of its original piece using “wax chasing,” an intricate process that involves carefully removing seam lines and patching cracks with heated soldering irons or tools (dental tools may work best). At this stage of “wax chasing,” artists will play an active role in ensuring the sculpture’s integrity as it progresses – signing off on its progress at regular intervals.
Once the wax has been cast, the foundry brings a team of workers to pour bronze into its ceramic shell. An artisan who operates the controls for the crucible (a metal container that holds molten bronze) is known as the lead pour. In contrast, another who maintains balance within it and pushes away dross (dross is unmelted copper) is known as the deadman.
The foundry team adds solid wax rods, and sprues, to the sculpture for more effortless bronze casting and as vents for air and gases to escape.
After moving the wax mold to the shell room, it is submerged multiple times into a fine ceramic fluid called slurry. It creates an additional one-time shell that ensures molten bronze correctly fills its intended cavity.
