There are other attempts to explain the name _lang yao_. In the catalogue of Mr. A. B. Mitford’s collection[262] it is stated that “the Lang family were a family of famous potters who possessed the secret of this peculiar glaze and paste. They became extinct about the year 1610.” Bushell[263] dismisses this with the comment that “the family is apocryphal and the porcelain antedated,” and in the same passage gives an alternative theory, viz. “this name has been derived by some Chinese of less weight from that of Lang Shih-ning, an artist protégé of the Jesuits,[264] who also lived in the reign of K’ang Hsi, and whose pictures are still appreciated.” The evidence for all these versions seems to be equally defective. They are, in fact, mere assertions, and the reader can take his choice of any of them, provided he does not insist on Mr. Mitford’s date (anterior to 1610), for all authorities are now agreed that the _lang yao_ is a K’ang Hsi production. The fact is that the name has been handed down without any explanation, and the current theories are of comparatively modern construction. The secret of the _lang yao_ consisted in the first instance in the knowledge of means to produce a brilliant red glaze from copper oxide. It was not a new discovery, but merely a revival of the wonderful “precious stone” red of the early Ming period.[265] The supplies of some essential ingredient for this colour had failed in the Chia Ching period,[266] and the secret of the true colour had been temporarily lost. This secret was now recovered probably by a potter of the name of Lang, and that name has been associated with it ever since. So far from the _lang yao_ being limited to the early part of the reign of K’ang Hsi or to the few years when Lang T’ing-tso might have been concerned with it, there can be little doubt that the _sang de bœuf_ red or red _lang yao_ is the special colour described in detail by Père d’Entrecolles in 1712, and again in 1722 under the significant name of _yu li hung_, or “red in the glaze.” The reader can judge for himself from the description given in the second letter[267]: “This red _inside the glaze_ is made with granulated red copper and the powder of a certain stone or pebble of a reddish colour. A Christian doctor told me that this stone was a kind of alum, used in medicine. The whole is pounded in a mortar and mixed with a boy’s urine and the ordinary porcelain glaze; but I have not been able to ascertain the quantities of the ingredients, for those in possession of the secret take good care not to divulge it. This mixture is applied to the porcelain before it is fired and no other glaze is used; but care has to be taken that the red colour does not run to the bottom of the vase during the firing. They tell me that when they intend to apply this red to porcelain they do not use porcelain stone (_petuntse_) in the body, but they use in its place, mixed with the porcelain