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As mentioned in the blog titled “Foundry process overview”,  the lost wax, or investment casting process must have a wax proof for each casting.  Also, when making multiple copies there needs to be a mold to make those wax proofs.

The Original Sculpture

Given that a mold is required, the first step is to determine how many molds will be required to make the needed wax proof (again, this is an exact copy of the original sculpture, made from the mold).  The number of molds for a given sculpture is dependent on the complexity of the sculpture.  For very simple relief-sculptures a single, one-piece mold can suffice.  The reason is that the back of the relief is unimportant and an exact reproduction is unnecessary.  A more complex sculpture, say a standing figure, will require at least one, two-part mold to enable reproduction of front and back.  As mentioned, the more complex the sculpture is, the more molds that will be required for a casting.  For demonstration purposes, I will be talking about two-part molds. 

With this in mind, the first thing that needs to be established is how many mold parts will be required to make a casting of any given sculpture.  The two sculptures above (Quanah Parker and the Teton Feather) will both require two-part molds.  The Teton Feather will have one, two-part mold.  However, the Quanah Parker sculpture, the man standing, will require two separate, two-part molds because of wand of feathers which he is holding in his hands.  These feathers will be removed from the original clay sculpture, molded separately and then reattach later on in the process. 

In the photographs below, the photo on the left shows the two different feathers being prepared for the first stage of the molding process.  That preparation consists of carefully laying the sculpture down on a bed of clay which has been rolled up into small balls.  This bed of clay balls will eventually become a "separator", dividing the front half of the sculpture from the back half.  Once the separator has been brought up to the edge of the sculpture, again carefully, the clay balls are then smoothed out and tucked in close up to the edge of the sculpture.  Vaseline is then applied to the surface of the clay separator.   The photo on the right shows both feathers with the separator smoothed out and ready for the first application of the mold making material. 

In the photo on the right, you will notice that a clay funnel, or cone shape has been added at the top of the sculpture.  This clay cone is attached to the end of the sculpture along with the additional raised clay tubes that branch off the funnel and lead back down to the sculpture.  These items will become very important later on in the process, the funnel and tubes will serve as a means to pour hot wax into the mold, when it's completed, to make the “wax proof”.    

As you can tell from the above photo of Quanah Parker (the man standing), the clay feather fan which he was holding has been removed.  The feather fan was molded separately (see above).   The same process of laying the sculpture on clay balls and smoothing them out to divide the sculpture in halves has already been done and the first coat of the (R/S) mold has already been applied.  The photo on the right is the same side of the sculpture with the final coat of (R/S) mold.    

Now that the first half of the (R/S) mold has been completed, it is time to apply the back half of the mold.  Also, if you’ll notice, there is another tube which was added around the circumference of the sculpture before the first half of the (R/S) mold was applied.  This tube was done differently than the funnel and tubes on the feather molds, as it serves a different purpose, all together.  While the tubes in the above feather molds were built up in the clay separator and left there throughout the molding process, the tubes in the mold of the man were carved out of the separator, making a trench.  In the end, the difference between the two is that the feather mold will have a hollow channel for wax to flow through, while the channel around the standing figure will eventually be negative space on one side of the mold and positive space on the other side of the mold.  This male/female connection will allow the two sides of the mold to “keyed” into one another, ensuring the (R/S) mold lines up properly, later on, when making the wax proof.  The reason that hollow tubes are not required on the standing figure is due to the structure and larger size of the mold, the base of the man is large enough to act as the funnel and requires no venting.  As a small foot note, I realize that the photo of the tube looks like it is raised and made of clay, however, while it is raised, it is the (R/S) mold from the first side.  The clay you see is just the residue of the clay after removing the separator.  The photo on the right is after the first coat of (R/S) mold has been applied.

This photo shows the application of the fiberglass shell which is also applied in halves over the (R/S) mold.  This rigid fiberglass shell acts as a support and prevents the soft (R/S) mold from distorting the wax proof.  Often times, small molds, depending on how thick and rigid the (R/S) mold was made, can forgo this step.

(To be continued)