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Unveiling the Artistry: The Intricate Process of Casting my Sculptures into Bronze, Part II

Updated: Feb 14

Unveiling the Artistry: The Intricate Process of Casting my Sculptures into Bronze, Part II.



The mystique of metal and fire...


Pegasus Soaring, Unicorn Version Patina Application. winged horse sculpture by Kindrie Grove.
Pegasus Soaring, Unicorn Version Patina Application.

The Process continued...



8. Firing the Mould


The mould is fired at high temperature in order to harden the ceramic and melt, or burn the wax out of the mould. The wax is drained out and collected for re-use beneath the kiln. This process takes several hours.


When the wax has completely melted away it leaves behind a hollow cavity ready to receive the molten bronze.


 

9. Casting and Pouring the Bronze


While the mould is being fired, it is time to carefully heat the bronze to is liquid state.


Bronze heats to molten liquid in preparation for pouring into the fired moulds
Bronze heats to molten liquid in preparation for pouring into the fired moulds


Crucible and furnace before the melting of the bronze.
Crucible and furnace before the melting of the bronze.

This critical stage requires skill and precision to ensure a successful casting, as any imperfections can affect the final result. The timing is planed so that the bronze reaches its pouring temperature at the same time as the mould firing is completed.


Setting the hot moulds into the sand bed for pouring.
Setting the hot moulds into the sand bed for pouring.

The moulds are carefully removed from the kiln and set in a sand bed with the tops upright and ready for pouring. The moulds must be hot when the molten bronze is poured in. If they are allowed to cool, they may crack when filled with bronze.


Lifting the crucible from the furnace
Lifting the crucible from the furnace

The crucible is lifted from the furnace by a pair of massive two-handled tongs, and placed in the collared pouring tool, often referred to as a pouring ladle, which allows the foundry team to hand pour the bronze from the heavy crucible with amazing accuracy.


Molten bronze is poured into the moulds
Molten bronze is poured into the moulds

The amount of bronze melted for the pour is calculated down to the last ounce to ensure that each mould is perfectly filled with no wastage.



Once filled the moulds are left to cool.
Once filled, the moulds are left to cool.


Once filled, the moulds are left to cool until the colour of the metal turns from the pink, orange of molten metal, to a dark grey.


Cooled moulds are ready for the bronze to be removed.
Cooled moulds are ready for the bronze to be removed.

 

10. Removing the Raw Bronze from the Mould


Once the bronze has cooled and solidified, the mould is removed to reveal the raw casting underneath. The ceramic shell is chipped away with hammer, chisel, Dremel and wire brush, meticulously cleaning it from all of the crevices and surface texture of the sculpture.


Raw bronze Polar Bears emerge from the ceramic shell of the mould. (Note the window cutout on the rumps.)
Raw bronze Polar Bears emerge from the ceramic shell of the mould. (Note the window cutout on the rumps.)


The foundry's ceramic shell chip mound! This is where the bulk of the mould is removed after a casting.
The foundry's ceramic shell chip mound! This is where the bulk of the mould is removed after a casting.

 

11. Finishing the Bronze


Pegasus: Soaring in raw bronze before finishing and wing attachment. winged horse sculpture by Kindrie Grove
Pegasus: Soaring in raw bronze before finishing and wing attachment.

Once the shell of the ceramic mould has been removed completely from the raw bronze, there is still a considerable amount of work to be done to finish the metal.


Sprue attachments and vents must be removed and the areas of attachment ground out and cleaned up. Windows that were cut out in the wax to facilitate the investment mould creation, also have to be welded back into place.


This stage is also where any imperfections that show on the surface are removed and the bronze is prepared for the final step of patination.

This requires a steady and deft hand to match the surface and texture details of the sculpture.


Perch for One, Rufous Hummingbird in raw bronze before finishing. sculpture by Kindrie Grove
Perch for One, Rufous Hummingbird in raw bronze before finishing.


 

12. Patination


The patina is a crucial step in finishing a bronze sculpture, enhancing its appearance and adding depth and character to the metal's surface. Patination involves applying chemicals to the bronze surface to induce chemical reactions that create various colours and textures.



Unbridled: Percheron Heavy Horse, finished bronze before patination. sculpture by Kindrie Grove
Unbridled: Percheron Heavy Horse, finished bronze before patination.

Before applying the patina, the sculpture must be thoroughly cleaned and degreased to remove any dirt, oils or residue that could interfere with the patination process.


The surface may be lightly sand blasted, or polished to achieve a smooth and even texture, ensuring the patina will adhere properly.


Final patina touches on Unbridled: Percheron Heavy Horse, photo of the artist, Kindrie Grove, working on the sculpture.
Final patina touches on Unbridled: Percheron Heavy Horse


Through a combination of chemicals and solutions applied in layers to the surface of the bronze, various colours and textures are achieved. Common chemicals used in the patination process include liver of sulfur, ferric nitrate, cupric nitrate, silver nitrate, and various acids. These chemicals react with the surface of the bronze to create colours ranging from rich browns and blacks to vibrant greens, blues and reds.


Trojan II - Liver of sulfur is applied cold and then scrubbed to reveal highlights before being rinsed off. horse sculpture by Kindrie Grove
Trojan II - Liver of sulfur is applied cold and then scrubbed to reveal highlights before being rinsed off

In addition to chemical application, heat is often used to accelerate the patination process and to control the colours and textures produced. The sculpture may be heated with a torch or placed in a kiln to reach the desired temperature.


Trojan II: Heat is applied via torch to get the sculpture hot enough for the cupric nitrate to be applied. patination process for a horse sculpture by Kindrie Grove
Trojan II: Heat is applied via torch to get the sculpture hot enough for the cupric nitrate to be applied.

To achieve complex and nuanced patina effects, the different chemicals may be applied in multiple layers while manipulating the surface with brushes, sponges or other tools. Steel wool is used to buff back raised areas to show the glow of raw bronze highlights through the layers.


This layering and manipulation allows for a high level of control over the final appearance of the patina.


Trojan II: Layers of cupric nitrate are sprayed onto the sculpture to achieve a green patina. Horse sculpture by Kindrie Grove
Trojan II: Layers of cupric nitrate are sprayed onto the sculpture to achieve a green patina.


Unbridled: Percheron Horse. Ferric nitrate is added to warm up the black of the liver of sulfur.
Unbridled: Percheron Horse. Feric nitrate is added to warm up and even out the blue/black of the liver of sulfur.

Pegasus Soaring, Unicorn version. Silver nitrate is added over liver of sulfur to achieve a pearlescent silvery grey patina. sculpture by Kindrie Grove
Pegasus Soaring, Unicorn version. Silver nitrate is added over liver of sulfur to achieve a pearlescent silvery grey patina.

Once the desired patina has been achieved, the sculpture is sealed and protected to preserve the finish and prevent oxidation or tarnishing over time. A clear protective coating, such as wax or lacquer, may be applied to the surface to seal in the patina and provide a durable barrier against environmental factors.


After the patina has been sealed and protected, the sculpture may undergo further finishing touches, such as polishing to highlight details and felt attached to the bottom surface to prevent the sculpture scratching what it is displayed upon.


I often use watercolour to black out where bits of ceramic shell may have been missed, and then apply a second thorough coat of wax before a final polish.


Aesop's Crow, Commissioned sculpture for a fountain during final finishing with black watercolour to black out any missed ceramic shell and a second coat of wax. sculpture by Kindrie Grove
Aesop's Crow, Commissioned sculpture for a fountain during final finishing with black watercolour to black out any missed ceramic shell and a second coat of wax.

Certificates of authenticity with my signature and seal, in a custom folio, with a care of bronze sculpture sheet, is included with each of my bronze castings so collectors can see where their piece falls within the edition for the sculpture.


Certificate package for one of my bronze sculptures, Kindrie Grove
Certificate package for one of my bronze sculptures

Overall, the patina process is a highly skilled and artistic endeavor that adds depth, richness, and character to bronze sculptures, elevating them from mere metal objects, to timeless works of art that resonate with viewers on a physical and emotional level.


Now the sculpture is ready to be unveiled, a culmination of creativity, craftsmanship, and dedication. It holds a timeless beauty, and an enduring legacy, rooted in thousands of years of skill and knowledge – a work of art that captivates the imagination and enriches the world with its beauty.



Trojan II, final finished bronze sculpture of a horse by Kindrie Grove.
Trojan II, final finished bronze

I wish to offer a heartfelt thanks to Bill Lalongue, and the folks at Pyramid Bronzeworks, in Kelowna BC, for their dedication to the craft of fine art bronze casting, and for their essential part in translating my sculptures into bronze.


I hope you enjoyed this two part blog series on the bronze casting process, and hopefully the long story wasn't too long!


 

Do you have other topics regarding my work that you would like me to post here? Let me know.


This space is to share my rather insular and reclusive creative life with collectors and friends who follow my work.


I am always happy to hear from you!


Logo image for Kindrie Grove
 

If you missed Part I of this in-depth photo essay on the bronze casting process, click here to read it now.





Unveiling the Artistry: The Intricate Process of Casting my Sculptures into Bronze, Part II

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