[169] An American writer has arranged the tests by which soft pastes may be distinguished from true porcelains under six heads. 1. _The file test._--Soft porcelain may be marked by a file. 2. _The foot test._--In hard porcelain the foot is generally rough and unglazed. This test is rather of value in distinguishing porcelain from fayence. 3. _The fire test._--Depending on the greater fusibility of the soft pastes. 4. _Chemical test._ 5. _Colour test._--Soft paste is generally mellow ivory by transmitted light, and this is especially true of ‘bone-ware.’ The hard paste tends to bluish shades. 6. _Fracture test._--The fracture is glassy to vitreous, and the glaze passes into the paste in the case of hard pastes (the subconchoidal splintery fracture is rather the point to observe); dry and chalky, and the glaze more or less separated from the paste in the case of soft pastes.--E. A. Barber, _Pottery and Porcelain of the United States_, New York, 1901. [170] De Réaumur, we must remember, had made some kind of hard-paste porcelain from Chinese materials. After that he fell back upon his devitrified glass. Something very similar had been made by Tschirnhaus many years before. [171] These, I think, are almost the only instances in which a distinctly seventeenth century decoration is to be found on porcelain. [172] These _trembleuse_ saucers of the early eighteenth century have a projecting ring into which the base of the teacup fits. [173] The extreme limits for this mark are 1712-62, but Chaffers says it was not used before 1730, according to another authority not before 1735. De Frasnay, in a note to his curious little poem in praise of fayence (1735), says: ‘_le secret du beau rouge n’est guère connu en France que d’un très petit nombre de personnes_.’ The point is of interest in connection with the origin of the _famille rose_ in China. We may here note that the minute quantity of gold--the source of all these pink and purple colours--is not necessarily introduced in the form of the tin salt, the purple of Cassius. But this difficult question will be best treated in connection with the history of glass. [174] Generally known as the Duc de Bourbon (1710-40). He was an enthusiast for the art of the Far East. An important work on Chinese art was published under his auspices in 1735. He imitated the painted hangings of the East, and even attempted to make Japanese lacquer. After his death, the two brothers Dubois, _épiciers à Chantilly_, migrated to Vincennes, and the Chantilly works were for a time neglected. See Gustave Macon, _Les arts dans la Maison de Condé_, 1903. [175] Of the many European imitations of the ‘Kakiyemon’ style the Chantilly is most successful, while the ‘Old Japan’ was best copied at Chelsea. No European imitation in porcelain of the Chinese blue and white approaches in brilliancy that made in Delft ware in the seventeenth century.