The Process

Lorne Wall’s ability to recall small visual details is just one of the reasons that his sculptures have such an amazing authenticity. In competitions held each year at the Calgary Stampede, artists are given 45 minutes to complete a sculpture on stage. Within that time he’s been able to create sculptures such as “Along the Fence Line”, an image he brought to life from a simple pencil sketch made years earlier. Each bronze work of art starts as a creative inspiration that is brought to life as a wax sculpture.

The process of transforming a wax sculpture into a bronze sculpture can take three to six months to finish, moving through a series of positive and negative forms. 

RUBBER MOLD:
Once the original wax sculpture is complete, it is sent to the foundry where it is painted with an even layer of rubber and then covered by a hard reinforced plaster shell called a mother mold.  This is done one half at a time, so when the first half has hardened, the sculpture is turned over and the same is done to the other half. On a large sculpture, it may be necessary to create even more molds one section at a time. When the plaster mold is later opened, the original sculpture (positive image) is removed and the rubber is rejoined within to create a detailed hollow cavity, or negative image of the sculpture.

WAX POSITIVE:
Heated wax (approximately 210 degrees Fahrenheit) is poured into the mold to evenly coat the inside. This process is called slushing and is repeated several times, allowing time for the wax to cool between each time until the wax wall within the rubber mold is about 3/16th” thick.  When the mold is opened and the rubber is peeled away, a hollow wax duplicate (positive) is removed.

CHASING:
Special tools are used to rejoin all of the wax sections of the sculpture back together and the artist works to make sure that the likeness is accurate, the thickness of the wax is consistent, and  that all of the seams are removed. This process is called “chasing”.

SPRUING AND GATING:
Special channels, which are made of wax, are strategically placed so that  the bronze will be able to reach all of the recesses within the mold when it is poured. Wax sticks of different dimensions called vents and gates are also affixed with heated tools that will become the pathways through which trapped gas will escape from the mold as the hot  bronze cools.

INVESTING:
The hollow wax sculpture is then dipped into a vat of “slurry” and immediately submerged in fine silicon sand. This is done repeatedly, allowing cooling time between each dip, until the ceramic shell formed around it is about ½” thick. Different colours of sand are sometimes used to in this process to provide a visual reference for the artist so that they can gauge the thickness of the mold.  Depending on what the shell has been made of, either plaster or ceramic, it is either placed in a steam chamber or baked in a kiln to melt the wax which is then “lost”, and poured out leaving a negative space to fill with bronze.

POURING:
The mold is again heated to a temperature of 1100 degrees to prepare it to receive the hot bronze which only begins to melt at 1700 degrees and is poured when it reaches 2200 degrees.  Bronze is intentionally coloured because it has many of the same characteristics as gold and it would be possible to confuse the two.

DEVESTING:
Once it has cooled, the mold is broken off with hammers and power chisel  leaving only the hardened bronze sculpture. It is then “chased” using a variety of tools, which depending on the size of the piece can range from large electric grinders to small pencil size polishing tools to restore the detail and remove any marks left behind by the mold.