Not till the Easter Fair of 1713 was the white porcelain offered for sale at Leipsic, and even then the specimens on sale were far from faultless. Only in the year 1716--in the interval a new description of white paste had been discovered--was the ware exhibited technically perfect. Thus in the space of some eight years, Böttger had not only succeeded in making an excellent imitation of the Chinese boccaro ware, of which the special merit was to withstand rapid changes of temperature, but he had once for all solved the great problem: he had produced a hard white porcelain, which has remained since that day the type for the whole of Europe.[153] Where, we may ask, did Böttger acquire the technical knowledge and the practical experience, so essential in work of this kind? All the other men who have made a name for themselves as breakers of new ground in the art of the potter--Palissy, Poterat, Wedgwood, and to these we may add the great Chinese superintendents at King-te-chen and the Japanese artists Ninsei and Zengoro--were either working potters themselves or directors of large factories. What opportunities had this youth--he was only sixteen when he came to Dresden, and already, it would seem, ‘well known to the police’--of acquiring the practical details of the kilns, the mixing vats, and the wheel?[154] So again with regard to the materials he employed. Not much light has so far been thrown on this point. We have a somewhat childish story about a certain hair-powder--the _Schnorrische Erde_--which turned up at the psychological moment and solved the question once for all. But porcelain is not to be made from kaolin alone. That is only the skeleton, as the Chinese say. We must find also the right kind of flesh to make the bones hang together. No mention, however, is made in the current narrative of any experiments on felspathic rocks. We know at least that this famous ‘hair-powder’ was a very pure white kaolin, found at Aue, near Schneeberg, in the Erzgebirge, and that china-clay from this source was the principal ingredient in the earliest porcelain produced. So in later accounts we find mention merely of different qualities of kaolin from Aue, from Seilitz, and other sources.[155] A few years ago the Meissen paste, it is stated, was composed of kaolin from three different sources 72 per cent., of ‘felspar’ 26 per cent., and of old clay worked up again 2 per cent. In this and in most other cases where felspar is mentioned as a constituent of a porcelain paste, we must probably understand some kind of petuntse or china-stone containing quartz and perhaps other minerals in addition to the felspar. The following figures show the composition of the paste at the beginning of the last century: silica 59 per cent., alumina 36 per cent., and potash 3 per cent. The glaze was at that time composed of calcined quartz 37 per cent., Seilitz kaolin 37 per cent., limestone 17·5 per cent., and porcelain pot-sherds 8·5 per cent.