What is the Clay door?
Mr. Gu often mentioned the term “clay door”: “Purple clay has its ‘clay door.' Before pounding, the clay is dormant and needs to be awakened with our wooden mallet, which opens the ‘clay door.' Pounding the clay is a significant skill. Properly pounded clay is elastic and ‘breathes,' with its ‘clay door' fully open. At this point, the clay is in its best state and ideal for making Teapots.”
In simple terms: it is a term used to describe the density or tightness of the particle distribution in the body of a fired purple clay Teapot. Lower density is referred to as a loose clay door, while higher density is called a tight clay door. The intervention of craftsmanship changes the movement of the purple clay particles and thus alters their distribution.
Further understanding: During the manufacturing process of a Purple Clay Teapot, the shaping techniques such as patting, pressing, scraping, and finishing cause a change in state. This change is not static and cannot be judged as better or worse; it varies according to the shape of the pot and the crafting technique used.
The clay door is present throughout the entire process of making a purple clay teapot, from creating the clay sheet, forming the body, using the rib tool, smoothing the walls and bottom, shaping the lid, spout, and handle, all the way to the firing temperature, which can affect the semi-closed pore structure of the purple clay particles (a lower firing temperature results in a relatively looser clay door, while a higher temperature leads to a more crystallized and tighter clay door).
It mainly manifests in three aspects:
Molding: When the body of the teapot is patted into shape, it results in a state where the clay door is tight on the outside and loose on the inside;
Clay: Different types of clay have varying shrinkage rates and degrees of cohesion, affecting the internal texture and resulting in changes in the clarity of the clay door;
Rib tooling: The use of a rib tool and any finishing techniques that smooth the surface of the teapot can increase the density of the outer surface, leading to a tighter clay door.
What is the function of the clay door?
The clay door is an important criterion for identifying a fully Handmade purple clay teapot versus one made with a mold.
In simple terms, a fully handmade teapot is formed by hand using a bamboo paddle, so the characteristic of the clay door is tight on the outside (surface) and loose on the inside (body). The outer surface has a dense particle distribution, which becomes even denser after finishing with a rib tool. However, the inner wall, without being pressed forcefully, has a relatively looser particle distribution, giving a loose clay door appearance;
For teapots made with a mold, the body is shaped by applying force with the hand or a tool inside a mold, resulting in similar pressure on both the inside and outside surfaces. Therefore, these teapots have a similar tightness in the particle distribution on both surfaces, meaning the clay door is generally tighter.