How the Lost-Wax Shellspen Ceramic Shell Process Works

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(1) First an original is made (sculpted in clay, foam, wax, wood, plaster or any workable medium / or for industry, the original is machined from hard jewelry wax, aluminum, wood, foam or any workable medium machined on a lathe and machined with drills and power tools).

(2) Once the original is made, a rubber mold, plaster mold, fiberglass mold, bondo mold, or similar mold is made from the original that a wax is cast into. Then the wax casting is pulled (released) from the mold. This wax casting is an exact duplicate of the original. Usually with sculpture, a semi-soft sculpture wax is used (victory-brown sculpture wax or similar) as after the wax casting is pulled from the mold the artist can refine and/or enhance the wax to the artist's style. Or for industry, usually a hard jewelry wax is pulled from the mold (hard / dense waxes are used in industry as they are precise and have little shrinkage). Also in industry the original is usually made a few millimeters larger as in the mold making process the wax casting will be slightly smaller than the original. As in industry the casting must be precise for machine parts such as turbo props for jet engines, precision parts for microscopes and other precision instruments and parts.

Artists can bypass the mold making process when making a one of a kind sculpture casting, by sculpting directly in wax, and/or carving the basic shape in Styrofoam, coating the Styrofoam with wax, sculpting the wax, and then chemically removing the Styrofoam and proceed with the wax in the following steps below. When using this process there is always the possible risk of a miss-casting and losing the original wax. As with this process you have no mold to pull a replacement wax from.

(3) Once you have your wax, and it is refined and correct (remember with the Shellspen ceramic shell process, if there is a fingerprint impression in the wax, this will come out exactly in the casting) then feeding gates (sprues) are adhered to the wax pattern and pour cups so the metal will flow to the casting.

(4) Then the wax pattern is coated with the liquid Shellspen ceramic shell slurry, stucco and refractory cement in a series of coating steps until the ceramic shell slurry is built up over the wax to a thickness between 0.6 cm to 1 cm [1/4 inch to 3/8 inch], (average, less on small wax patterns, more on large wax patterns). After the ceramic shell slurry has dried, it proceeds to the next step.

(5) The wax pattern coated with the ceramic shell is placed in a furnace with an immediate and intense heat of  816 Celsius (1500 degrees Fahrenheit) or more, and the wax is melted (removed) out of the ceramic shell. This process also hardens (vitrifies /fires) the ceramic shell (similar to how pottery is fired in a kiln); thus leaving your ceramic shell hollow where the wax pattern once was.  Also the wax can be removed by boiling or steaming (Autoclave) the wax out and then placing the ceramic shells in a furnace to (vitrifies /fires) the ceramic shell.

(6) Then the ceramic shell is patched (release joints filled, cracks patched. and hydraulic pressure points reinforced if necessary) and air and heat dried.

(7) The ceramic shell molds are preheated in a furnace, and then molten bronze (or any metal, brass, aluminum, iron, gold, silver, etc.) is poured into the hollow ceramic shell mold via the pour cups and gating system to fill the mold.

(8) After the castings have cooled, the ceramic shell is broken away (the ceramic shell is a waste mold, meaning it can only be used once) with hammers and chisels (or shakers in industry) and then sandblasting to remove the ceramic shell from fine detail. Now a rough casting is complete.

(9) Then the feeding gates (sprues) are cut off, the release joints are chiseled off and the surfaces where these were, are recreated to match the sculptures surface with hand and power tools. For industry, the castings are sometimes machined on a lathe and/or drills and power tools are used for precision industrial parts.

(10) The final step in completing the casting is a patina finish and/or high polish finish. The patina finish is a process of a series of chemicals, applied (cold or with heat) to achieve a different look of the original bronze color from browns, blacks, greens, blues, to exotic colors. Also for sculpture and industry “if needed”, the castings are high polished using a series of power polishers with polishing compounds. Also sometimes bronze scultures are painted to give a certain look.