Materials
The clay is taken from five metres underground and weathered naturally for over six months before use. The kiln fuel is pinewood collected from high mountains, chosen for its resin content.
How It Is Made
The archive records the working steps as clay preparation, slow-wheel shaping, coil building, natural drying, carved lettering and ornament, bisque-firing and glazing, and dragon-kiln firing — with clay preparation, kiln loading, and firing the most exacting. The whole process is worked almost entirely by hand, and the archive describes it as strict in its demands on season, temperature, humidity, and light, with experience passed down for reading the weather. The fuller sequence runs: digging the clay, sun-drying, stirring, filtering, heaping, kneading, shaping, carving, glazing, drying, loading, firing, unloading, finished ware.
1. Clay preparation (zhini). The clay is prospected and dug, rolled and crushed, aged, spread in the sun, cleared of impurities, crushed again, and kneaded to expel the air. Clay for cups and dishes is repeatedly washed, filtered, settled, and pounded, so that the finished piece will not crack.
2. Shaping (zhipi). Small pieces are pinched directly by hand or formed on the wheel; larger and mid-sized vessels are built by the coiling method (panniao panzhu) — clay rolled into even cylinders, a base patted out into a disc with its rim squeezed up about two centimetres, and the coils wound round it, pressed firm with the right hand inside and the left outside, each new joint offset from the last so the wall does not collapse. Wheel-thrown work (lapi) begins with thorough kneading with added water to drive out air, the clay ball fixed at the wheel centre with the speed held within 250 rpm; the wall is opened with the thumbs and raised with even pressure, the rim closed, the surface wiped smooth with a wet cloth, and the form trimmed (lipi) — the thickness judged by tapping, a thick wall ringing low, a correctly thinned one giving a crisp sound, since different parts of a body are trimmed to different thicknesses against uneven shrinkage in firing.
3. Drying (liangpi). The shaped bodies are set on wooden racks to dry in the shade or laid out in the sun. Shade drying is preferred: damp left inside a body will split it when heated, and the drying sheds are low brick or adobe rooms tiled with small tiles, kept airy so the bodies dry slowly and evenly. Bodies dry for twenty days or more before entering the kiln.
4. Carving and glazing. Lettering and carved ornament are cut before firing. For glazing, the archive records five hand methods — dipping, pouring, swirling, spraying, and brushing — with the layer kept even and of suitable thickness, and the fluidity of each glaze taken into account. A printed-transfer decoration is also recorded as a later industrial variant, fired at 780 °C.
5. Loading the kiln (zhuangyao). The bodies are stacked from the kiln tail up toward the head, large bodies set mouth-to-mouth in pairs with smaller ones nested inside, each stack left clear of the stoke holes so the flame can move. The kiln doors are bricked up and sealed with lime mortar against draughts. Glazed bodies must not touch one another, or the melting glaze would fuse them together. The fire path is arranged "tight at the front, loose at the back" so the whole kiln fires evenly.
6. Firing (shaoyao). Firing requires "three dry": the kiln dry, the bodies dry, the wood dry. A firing normally runs forty-eight hours, and twenty-four more if the three conditions are not met. The fire starts slow, then medium, then strong, quickening only past 400 °C, and the final temperature reaches 1,200 °C. The firing passes through four stages: evaporation, to 600 °C, drying out the last moisture; oxidation, 600–1,000 °C, held at 900–980 °C to clear the residual crystal water, organic matter, and carbon; reduction, 1,000–1,200 °C, in which ferric iron is reduced, the glaze vitrifies, and the body hardens, held at 1,210–1,250 °C to even the heat through the kiln; and cooling, 1,250 °C down to 40 °C — fast while the ware is still molten, slow between 800 and 400 °C lest it crack, fast again below 400 °C with the peep holes opened. The pinewood is fed by four firemen standing two by two along the kiln back, each working one peep hole, opening and closing the pairs in turn and moving toward the tail as the bodies turn from peach-red to bright red. A firing runs more than three days without pause and calls for firemen with decades of experience working together.
Related Houses
- Qianshantianzhu (潜山天柱陶瓷) — Qianshan Tianzhu Ceramics Co., Ltd., Doumu
township, Qianshan, Anhui
Source: China Time-honored Brand Digital Museum, Ministry of Commerce (MOFCOM). Craft record from the archive of Qianshan Tianzhu Ceramics Co., Ltd. (brand 潜山天柱陶瓷 / 痘姆古陶); condensed and translated from the official Chinese record, with no information added.