Some of the celadon-glazed pieces will have a black satin matt glaze on the bottom half of the piece. I do this for a few reasons, mostly aesthetic. It really helps to pop the lighter tone glaze, and accentuate the surface. It also provide something of a visual pedestal for the pattern to sit on, visually reinforcing the idea that this is a special object. To get a sharp, clean transition between the two glazes, I will paint a band of wax over the celadon top of the piece, and over the celadon under the foot ring. The area to be glazes black is left free of wax, and the celadon is whipped away with a sponge. Once it has dried a bit, I will dip the bottom half of the piece in the black glaze, and the wax will protect the celadon, giving a clean, sharp transition line between the two glazes, and avoiding any accidental splashes or speckles of the black onto the lighter glaze.