After completing the pod birds (10/8 blog) and the figure (10/20), I began to gate the pieces in preparation for making the investment mold and then the bronze pour. The gating process becomes more challenging if the piece has multiple angles and varied thicknesses, especially if some areas are very thin. All of the items I was gating fell into this category (except for the flat base for the figure). It is important to make sure that once the wax is burned out of the investment mold, the remaining air space allows for an uninterrupted flow of bronze through the mold. I chose to use the bottom gate method in which the bronze flows down from the pour cup to the bottom of the main gate and then travels back up through the upward slanting sprues into each piece, forcing the air in the mold ahead and out the vents. This technique will create a more efficient flow of bronze in the birds - entering through the thicker body and then exiting the thin legs and out the vents.
Gating for multiple objects with multiple angles is time consuming. Any projections which differ from the natural upward path of the bronze flow must be connected with the appropriate angle of gating or venting...gates to bring in bronze, vents to allow air to travel out the top of the mold. In the case of the birds, this meant attending to the bulging eyes, the tips of the wings and tails, and the toes and heels of the feet. The figure had similar issues in its limbs. The first step for me was to attach as many connecting gates as possible on each piece before attempting to attach them with sprues to the main gate. This allowed for easier access and less handling after the pieces were attached to the main gate.
The final step in gating was to attach each piece by a sprue to the main gate, complete the venting process, and try to keep the structure compact so that the eventual mold will be a manageable size. Given number of pieces and their irregular shapes, the final structure became a maze of intertwined bird legs, bird nests, and human limbs, not to mention several dried poppy seed pods with stems. (If you are into solving puzzles, this is a fun challenge.) Hopefully everything is securely attached and will withstand the pouring of the investment into the mold flask. Fingers crossed!
Cynthia Smith, Maine artist, originally from Connecticut. Taught art at secondary level for 35 years, retired in 2004. Sculpts in bronze, wood, stone, clay & plaster. Her work can be seen at several mid-coast Maine galleries and shows.