Diagram depicting a speculative version of the ancient Chinese piece mold casting process:
1) a model of the You vessel with lid is prepared out of loess (a fine-grained refractory soil found throughout northern China) and baked dry;
2) the piece mold segments need to account for undercuts in the model; half of the upper part is covered in loess to form the first section of the mold; it is smoothed and keyed to ensure alignment of the next section;
3) the second section of the mold is built up alongside the first and allowed to dry and harden; the mold segments are carefully removed from the model;
4) in order to make the core, the top two pieces of the mold are reassembled and packed tightly with loess to form a replica of the original model and to add a base;
5) the mold is opened and the outer surface of the loess replica is cut back (pared down) to create a core that, once repositioned in the outer mold, will help define the space to be filled with molten metal;
6) at this stage additional details can be carved into the face of the mold;
7) the mold sections are reassembled around the core and a funnel/gate is cut into the mold; the assembled mold is baked until dry and filled with molten bronze;
8) the mold is removed and the gate cut off; except for some basic removal of flashing and sprues, the surface would merely be polished;
9) the bronze lid and body of the vessel (produced by the same process) are fine-tuned to fit perfectly.