The causes of glaze variability are discussed and related to pottery practices. It is concluded that Song Dynasty potters developed and adapted preexisting technology in an effort to achieve particular visual results. Electron microprobe analyses and scanning electron micrographs of Song high-fired glazes, low-fired lead glazes, and overglaze enamels were compared with Pre-Song and Yuan Dynasty glaze compositions and microstructures to determine the degree of uniformity in various glaze types and their change with time. -- AATA