Unveiling the Artistry: The Intricate Process of Casting my Sculptures into Bronze, part I.
A Time-honored, Centuries-old Process that marries artistry with Metallurgy.
How are my bronze sculptures made?
It is the question I receive the most when speaking with people about my work.
I usually reply with a question on my own...
Would you like the long answer, or the short one?
Folks usually ask for the long answer, but invariably I watch as their eyes glaze over, while I try to list all of the steps involved in the translation of my clay sculptures into an identical cast bronze version.
Finding a way to describe it simply and precisely can be a challenge, to say the least.
Lost Wax...
the short version
This method involves creating a wax model, encasing it in a mould, melting out the wax to leave a cavity, and then pouring molten metal into the cavity to create the final piece.
Now for the long version of how my Sculptures are cast into bronze.
Lost wax bronze casting is a fascinating journey that transforms a delicate and intricate artwork into a timeless masterpiece. Join me as I delve into the intricate process of casting a sculpture into bronze, exploring each step in detail, and uncovering the magic behind this timeless art form.
Some History...
This ancient technique, dating back thousands of years is believed to have originated in ancient Mesopotamia around 3500 - 3300 BCE. It marries artistry with metallurgy, resulting in stunning creations that captivate viewers with their beauty and craftsmanship. It has been used by ancient civilizations such as the Egyptians, Greeks and Romans for creating complex metal objects, sculpture, tools and jewelry.
The process has evolved over time, with advancements in materials and techniques, but the basic principles remain the same.
1. Inspiration & Design...
Every bronze sculpture begins with inspiration, a spark of creativity that ignites the artist's imagination. Whether it's a muse from nature, mythology or the depth of the artist's own mind, the initial concept takes shape through sketches, maquettes, and meticulous planning.
The design stage is a crucial step where the artist refines their vision, considering proportions, composition and details that will bring the sculpture to life.
2. Sculpting the model
With the design finalized, the artist begins sculpting the model using an oil or water-based clay. I use an oil-based polymer clay that is constituted with oil, wax and grease. (J Mac is my favorite brand)
This clay never dries, and I am able to recycle it into new sculptures once the initial mold has been made.
This hands-on process allows the artist to imbue the sculpture with personality and emotion, shaping each curve and contour with precision and care. The clay model is where the true creative vision takes shape.
If I am working with a maquette, I keep it close at hand when sculpting, so I can check on positions and composition, using a pair of calipers to ensure the scale up is correct.
When working without a set of drawings or a maquette, I will use photo sources, and paintings I have done as a starting point. I then allow the inspiration for the piece to guide me in bringing it to life.
It is a beautiful, deep meditative process, which I liken to falling into the sculpture and forgetting everything else during that creative time.
3. Creating the First Mould
Once the sculpture is complete, the first mould is created using rubber silicone and plaster. This mould is a negative impression of the original artwork, and is carefully crafted to capture every detail of the sculpture, including the the artist's fingerprints!
The flexible rubber silicone records the intricate surface texture of the original clay, while the plaster, called the mother-mould or over-mould, provides support and structure.
The rubber silicone is painted on in successive layers, with a dividing dam and registration pegs, so it can be opened to remove the original clay sculpture, and the wax versions when they are created at later stages.
Depending on the complexity of the original sculpture, parts will be removed and moulded separately and then re-assembled in the wax.
This initial mould serves as the foundation for creating multiple wax copies of the sculpture for the planned edition.
4. Making the wax copies
After the original clay is removed, the mould is put back together, and wrapped tightly to secure the seams. Melted wax is poured into the mould cavity, allowing it to coat the entire mould and take on the shape of the sculpture.
This is done by rolling the mould to ensure the wax settles into each section. Once the wax cools and solidifies, another layer can be poured in to add to the thickness of the first layer (up to 1/4 inch)
This process will be repeated for each successive casting of the sculpture as the rubber silicone mould is reused to create each additional wax.
5. Chasing the Wax
When the wax versions of the sculpture come out of the rubber silicone mould, they are not perfect. There are often places where excess wax pools along the seam lines, and there are also areas that do not fill completely, leaving pits or bubbles that require filling.
A softer wax is used to fill these holes, and heated knives are used to cut away excess wax along seam lines.
If parts of the original sculpture were removed and moulded separately, they are now reassembled in the wax to make sure the sculpture is identical to the original.
6. Preparing the wax for the investment mould
Once the wax is chased and reassembled, it is prepared for the final investment mould.
This mould will be made from ceramic and requires vents, and a cone made from wax, to create an opening for the molten bronze to be poured into the mould.
Vents, which will allow displaced air to escape when the bronze enters the mould, are attached at this stage to ensure there are no gaps or bubbles that will ruin the casting.
In order to ensure that the ceramic creates a continuous coating, both outside the wax version, as well as inside, a section or window, is removed from the wax version to help facilitate this.
This opening also makes sure that the inside portion of the mould does not separate from the exterior portion.
7. The Final Mould
Once the wax copies are complete and assembled into a 'sprue tree' (small works are often assembled into trees with multiple copies attached together). The tree is coated with layers of ceramic material by way of a slurry mix, then tossed with fine grain ceramic powder which sticks to the wet slurry.
Time is required for each coat to dry before the next is applied. Courser material is used for the outer layers once all of the details in the wax are captured within the finer, inner layers.
When the durable ceramic layers have been built up to about 1/4 inch thickness, the mould is ready for firing.
End of part One
Unveiling the Artistry: The Intricate Process of Casting my Sculptures into Bronze, Part I
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