Hand-Thrown Stoneware Vase

Details

A wheel-thrown vase from a studio pottery in Puducherry, in a stoneware body fired to 1240 C in an oxidising electric kiln. Stoneware and earthenware look identical on a shelf and cost very different amounts to make, which is why earthenware fired at around 1050 C is routinely sold as stoneware. The difference is measurable in one number: water absorption of the fired body, tested by ASTM C373. Vitrified stoneware takes up under 1 percent. Earthenware takes up 10 to 15 percent, which means it is a sponge with a glaze on it, so water seeps slowly through the wall, the base sweats and it leaves a ring on a wooden table within a day. The second thing sold loosely is the throwing. A slip-cast vase is poured into a mould, and a hundred of them are dimensionally identical with a perfectly smooth interior; a thrown one carries the spiral of the potter's fingers up the inside wall and no two are the same height.

• Water absorption under 1 percent by ASTM C373, so it holds water with no liner and does not sweat
• Fired to 1240 C, not the 1050 C that produces earthenware
• Glaze lead and cadmium below detection by ASTM C738, tested on the glazed surface
• Thrown on a wheel, so throwing rings are visible inside and dimensions vary about 5 percent piece to piece
• Wall thickness 5 to 6 mm, foot ring turned and unglazed so it does not fuse to the kiln shelf
• No decal, no lustre and no overglaze that can chip off
• Stoneware is hard, which also means it is brittle. It will not dent or scratch, and if it goes off a table it breaks rather than chipping. And the glaze pools a little deeper on one side than another, because it was poured by a person over an uneven wall.