During the Joseon period, bone ashes or golhoe were one of the primary materials used to protect and smoothen the surface of lacquerware. This substrate was gradually replaced by clay materials similarly called gorae in the modern period. This article examines the causes of this transition. Scientific analysis and textual records testify that bone ashes served to be the essential substance of lacquerware throughout premodern Korean history from the Three Kingdoms to Joseon. However, around the beginning of the modern period, lacquer artisans began to diversify formulas of bone ashes. Nowadays, Intangible Cultural Properties, the nationally designated artisans who are obligated to maintain and transmit traditional crafts, use an array of materials including clay, clay ashes and charcoal ashes. By analyzing the composition of bone ashes used by Joseon master craftsman and that of clay materials used by Intangible Cultural Properties, this paper concludes that three factors prompted the modern transformation of lacquerware materials. First, the disintegration of the system of official craftsmen, along with socio-economic changes of Joseon, obstructed the supply line of bone ashes in the late Joseon. Second, the modern technique of inlaying mother-of-pearl did not require bone ashes as the primary substance any more, although it was proven effective previously. Last, industrialization under the Japanese colonial rule led to increased demand in lacquerware, and therefore, artisans experimented with new technologies to meet such demand and selected substrates accordingly. These innovative artisans later became forefathers of the lineages of Intangible Cultural Properties.