How It Is Made
Official materials record a saying that seventy-two workman steps go into one vessel, with the smaller steps numbering beyond a hundred. The traditional flow is given in six main stages.
1. Clay preparation (niliao jiagong). The clay is selected, crushed, puddled, settled, filtered, and aged. The official materials' account of the old method, drawn from kiln-site excavation, has the clay dug near the kilns, sun-dried, crushed, and stirred in water in round settling pits, the fine slip running off into a second pit; when the water has penetrated to the right degree the clay is dug out and stored to age.
2. Glaze preparation (youliao peizhi). Most glaze materials are lean and hard, crushed under a stone roller or in a stone mortar, then stirred in vats with the fine floating material skimmed from one vat into the next, several times over. The fine materials are dried, cleared of impurities, sieved, and kept separately; at use they are proportioned and mixed with water, the fineness tested by rubbing a little between finger and thumb, the density judged by an experienced worker's feel.
3. Mould making and decoration (muju zhizuo; kehua yinhua). Forms are designed and made up in body clay. Where patterns are wanted they are carved into the half-dry piece, or printed from moulds: a carved mould pressed against the soft body prints the pattern inside the vessel, and with a counter-mould carved on its inner face the pattern can be printed inside and out at once, which official materials note raises output considerably.
4. Shaping (chengxing). Round wares are thrown on the fast wheel (lulun che), a stone disc turned by a stick. Because the wheel's speed and diameter were limited, surviving old pieces are generally within thirty centimetres — official materials's saying that Ru does not exceed a foot. Carved and figural pieces were shaped by hand on the slow wheel, mostly as single pieces, and complete survivors are few.
5. Bisque firing and glazing (sushao; shiyou). Ru ware is fired in two stages. The dried raw body is pre-fired at about 800 °C to strengthen it and raise its absorption, then glazed by dipping or spraying; glaze tears, blisters, and pinholes are trimmed away with a bamboo knife or a brush.
6. Firing (shaocheng). Each piece stands on spur supports (zhiding) of high-alumina clay — three, five, seven, or nine of them, their tips pinched flat like sesame grains — set on a clay disc inside a saggar (xiabo) of refractory clay; the spurs are used once and broken away from the finished foot, leaving the whole vessel glazed. The old kiln was horse-hoof shaped, fired with wood or coal through wet-removal, oxidation, reduction, soaking, and cooling; the Song firing temperature is given as 1,100–1,200 °C.
Official materials also sets out the modern flow kept alongside the traditional one: body and glaze milled in ball mills, slip casting, hand throwing, and machine pressing, then glazing and firing.
Related Houses
- 弘宝斋 (Hongbaozhai) — Henan Hongbao Ru Porcelain Workshop Co., Ltd.,
Ruzhou, Henan
Source: official materials published by Henan Hongbao Ru Porcelain Workshop Co., Ltd. Craft record from the house's own published record; condensed and translated, with no information added.