Rouen porcelain is soft-paste porcelain made in the city of Rouen, Normandy, France, during a brief period from about 1673 to 1696. It was the earliest French porcelain, but was probably never made on a commercial basis; only nine pieces are now thought to survive. Rouen had been a centre for the production of Rouen faience (tin-glazed earthenware pottery), since at least the 1540s. Louis Poterat, the owner of the porcelain factory, came from the leading family of faience producers in the city at the time, and continued his faience production in another factory. History In 1644 Nicolas Poirel, sieur (lord) of Grandval, obtained a fifty-year royal monopoly over the production of faience in Rouen. By 1647 a factory owned by Edme Poterat (1612–87), who was probably an experienced potter, was producing faience, by arrangement with Poirel. Louis Poterat, eldest son of Edme, was granted a monopoly in 1673 for the making of porcelain in all France. The monopoly made no reference to an earlier one granted in 1664 to Claude Révérend, a Paris importer of Dutch pottery, which does not seem to have resulted in any successful manufacture. Révérend claimed to have perfected the process in Holland; it was perhaps just a sort of faience. In the 17th century Europeans were unaware that very specific clays, high in kaolin, were needed for porcelain, and also that a very high firing temperature was needed, in fact one higher than most European kilns could have reached, even if the potters were aware of the need. Many thought that the translucency of the Chinese porcelain they sought to emulate would be achieved if the paste included generous quantities of ground glass. The product resulting from these attempts is called soft-paste porcelain, which despite many disadvantages proved an acceptable substitute for true Asian hard-paste porcelain in both England and France, being manufactured until after 1800 in both countries. For example, the leading French factory, Sèvres, continued to make both types until 1804. In the 1670s the only soft-paste porcelain to have been produced in Europe was the Medici porcelain made for a brief period in Florence a century earlier. This was made from about 1575 to 1587 as a project sponsored by Francesco I de' Medici, Grand Duke of Tuscany. Some 60–70 examples survive, nearly all in various museum collections around the world. Like Rouen porcelain, they are nearly all in underglaze blue