A collection of 70 black ware shards excavated from 16 kiln sites in South Korea and dating from the 3rd – 13th centuries were studied using optical microscopy, scanning electron microscopy, and electron beam microprobe analysis to determine the range of technological variability in composition, microstructure and firing temperature. Materials analysis provided a means of deconstructing and reconstructing the development of (1) consistent high temperature firing, (2) unintentional ash glazing on black ware, (3) intentionally applied black glazes, (4) the relationship of grey and black glazes to green and white ones. This paper addresses issues of the influence of high-firing technology on glaze development and the development and continuity of the black glaze tradition. In addition, the black glazed Onggi ware of the late 19th century was compared to the earlier black-glaze tradition, once stabilized in composition in the Koryo dynasty, and results suggest a technological connection with the earlier tradition.