Quent Cordair Fine Art

Hello again and thank you for joining me for this Artist’s Studio.
The “mold” - the rubber and plaster shell, has been completed now and is ready to produce wax castings. It is the equivalent of a negative in photography (remember those?), where the image of the sculpture has been captured as negative space. The next step is to pour molten wax into the mold, rotate the mold around so that the wax just coats the inside, and pour the excess back out. This is called “throwing a wax”.

The wax is poured in and out this way until a layer is built up about 3/16 of an inch thick. This creates a hollow wax casting so that the bronze will be hollow as well. Remember that each wax casting will be used to create a bronze casting. You can see the mold of the book & hand split open to retrieve the red wax casting.

You can see how the “shim” around the middle of the piece in the moldmaking installment has divided the piece into 2 pieces at the waist. These castings are cut up further into managable sizes, and pieces are also cut out of the castings leaving “windows” (the back of the head has one). The castings are touched up or “chased” at this point for air bubbles, dings, scratches and such. Each piece is then attached to wax “cups” with “sprues”- the brown branch-like connections on the head and torso pieces- we’ll come back to these in a minute.

The completed wax assemblies will later be coated with ceramic to form a second mold into which molten bronze can be poured. The “cup” and “sprues” form the pathway for the bronze to flow through after the wax is melted out of the ceramic mold or “shell”; when the wax cup is melted out of the the ceramic mold, it forms a funnel and the sprues form pipes to disperse the bronze to different parts of the piece.

Hello again and thank you for joining me for this Artist’s Studio.

The next step after coating the clay sculpture with rubber mold compound, is to encase the rubber in a shell of plaster to hold its shape after the clay sculpture is removed from the inside. Hemp (yes, hemp) is dipped in plaster and laid directly on the rubber mold to create the shell or “mother mold”, which will remove by splitting like a clamshell.

The division line is marked by those big round tabs around the outside of the piece- they are where bolts will go through to hold the empty mold halves back together when pouring wax into them (I think the mold makes kind of an interesting sculpture in itself at this point). After the plaster cures hard, the mold is split open and the rubber is peeled off the sculpture in sections which now fit into the plaster shell. All remnants of clay are cleaned out and the mold is reassembled in sections for our next step of casting wax copies.

Hello again and thank you for joining me for this Artist’s Studio. We are now at the foundry and readying the piece for mold making. As a quick preface, I will summarize the casting process for you:

1. first a rubber and plaster mold is made on the clay sculpture
2. the clay is removed, and hollow wax castings are made from the mold
3. the wax castings are encased (or encrusted) with ceramic
4. the wax is melted out, and molten bronze is poured into the hot ceramic mold or “shell”
5. the bronze pieces are chipped out of the ceramic and welded together, ground, polished etc.(”chasing”)
6. last,but certainly not least, the bronze sculpture is given a “patina”- a chemical treatment to color and finish the bronze

The clay sculpture must first be prepped for the rubber part of the mold which will be painted on in layers. The fin encircling his torso is called a “shim”, it’s a piece of thin metal which will create a separation in the mold to make pieces which are small enough to handle easily. The round shape on the back creates a “lock” so that the cast pieces will go back together where they are supposed to.

The finished mold will now have two separate parts, which in turn will each be split again like a clamshell. (keep watching and all this will start to make sense) Note the large white piece in the background which has 3 shims to make 4 smaller molds out of it.

The blue is the rubber mold material. It is a catalyzed compound that comes in 2 liquid parts — when they are mixed, the two react and set up into rubber after a given amount of time. Successive layers will be painted on, later layers being thickened to a frosting like consistency to speed up the process after the surface detail has been captured.

Again, note some of the other pieces in the background that are in later stages. If you look closely on the right in the first photo, you can see that the book has already received several coats.

Hello again and thank you for joining me for this Artist’s Studio. This installment will wrap up the details of the clay sculpture. Here I have included close ups of the finished hand, shoes, and face which have been sprayed with a clear acrylic coating to protect the clay’s surface and help the rubber mold release from the sculpture when it is removed. The piece is now finished in clay and will be taken to the foundry to begin the mold-making and casting processes.

Hello again and thank you for joining me for this Artist’s Studio. The next step from here is to sculpt the book with the hand holding it, which will be cast separately. This may seem like a trivial step, but gives an understanding of how a sculpture must be thought out to accommodate the casting process as it is being designed. Later, as we go into the mold making process, the need for casting a sculpture in several pieces will be easier to understand. Larger or more complex pieces may have to be cut or sculpted in many pieces to be extracted from the molds or just to be able to handle and move them during all phases of casting.

Here I have glued and clamped some pieces of wood as an “armature” or core which is then covered with clay just as with the figure. The hand will be part of the same casting, and the arm will just terminate out of sight under the book against the other “stump”. The book is then mounted on a base using a piece of pipe, so that it is ready for the mold making process.

Next time should wrap up the details of the piece (and I will include a close up of the finished face for Sara who was kind enough to post a comment) and then it’s off to the foundry to start mold making and casting.