It will be convenient here to consider another type of decoration which was probably in use in the early periods of the Ming dynasty, certainly in the reign of Wan Li, and which has continued to modern times. This is the decoration in white clay varying in thickness from substantial reliefs to translucent brush work in thin slip or liquid clay, which allows the colour of the background to appear through it. The designs are painted or modelled in white against dark or light-coloured grounds of various shades--lustrous coffee brown (_tzŭ chin_), deep blue, slaty blue, lavender, celadon, plain white, and crackled creamy white--and they are usually slight and artistically executed. The process, which is the same in principle as in the modern _pâte sur pâte_, consisted of first covering the ground with colouring matter, then tracing the design in white slip (i.e. liquid clay) or building it up with strips of clay modelled with a wet brush, and finally covering it with a colourless glaze. In this case the white design has a covering of glaze. When a celadon green ground is used the design is applied direct to the biscuit and the celadon glaze covers the whole, but being quite transparent it does not obscure the white slip beneath. Sometimes, however, as in Fig. 3 of Plate 75, the design is unglazed and stands out in a dry white “biscuit.” Elaborate and beautiful examples of slip decoration were made in the K’ang Hsi and later periods, and Pére d’Entrecolles, writing in 1722, describes their manufacture, stating that steatite and gypsum were used to form the white slip.[189] The Ming specimens are usually of heavier make and less graceful form, and distinguished by simplicity and strength of design, the backgrounds being usually lustrous brown or different shades of blue. They consist commonly of bottles, jars, flower pots, bulb bowls, dishes, and narghili bowls, and many of them were clearly made for export to Persia and India, where they are still to be found. On rare examples the slip decoration is combined with passages of blue and white.