## Lecture Thirteen, February 16, 1982 ### Rational Development and Use of Molds: After obtaining a mold, the first step is to understand how it opens—whether it squeezes the bottom onto the body, or the body onto the bottom. The second step is to record measurements: measure the belly diameter to match the body, then match the bottom and lid. In our production knowledge, we should understand some scientific principles of clay materials: In our raw materials, the mineral clay itself contains organic colloidal substances, so once mixed with water, our clay can bond together. Suppose, when beating the body cylinder, if it is beaten too small, after placing it in the mold and squeezing with hemp cloth, the molecules inside become relatively compact due to external force, while the molecules on the outside (surface) are pulled apart because the body cylinder is too small to fill the space, destroying the density between molecules and causing the molecular density to crack. When such a body cylinder is scraped with a rib tool, the surface molecules are compressed again, which is actually the compression of the body cylinder. Because the top and bottom are held by the lid and base, the body cylinder at this point seems taller than its original form. Another phenomenon is that the body cylinder may develop a waist bulge, which is caused by insufficient expansion. Therefore, the raw body cylinder must be just right, so that the expanded piece will be good. One cannot rely entirely on the mold; the mold only serves a shaping function. After we obtain a mold, we must also be careful whether there are excess plaster bumps on the mold. If there are, they must be removed; otherwise, the expanded piece will have depressions that are very difficult to fill smooth. Pressing spouts: Spouts must be pierced through first before pressing. Even spouts with posts must be pierced through before pressing. The post area can be marked in advance. After placing the raw spout material in the mold, simply press with your hand at the post area. For some small posts that cannot be pressed by hand, small tools can be used as substitutes to fill the space. The purpose of using molds is to standardize specifications, improve efficiency, solve technical difficulties, simplify high-difficulty techniques, and improve quality. If using a mold takes more time than manual operation, then such a mold is unreasonable. Originally, using molds can relatively improve quality and reduce defects—