[2] The plants are harvested in July, before they flower, and the leaves are stored in earthenware jars of water for several days to extract the pigment.
The leaves are then removed and the water is mixed with lime from powdered oyster or clam shells to create a base.
[1][2][3] Fabric to be dyed is soaked in the resulting liquid (which stains it yellow) and then dried in sunlight, which activates the pigments and turns the cloth a deep blue.
The current master of this process, designated a Living National Treasure, is Jung Gwan-chae, who has cultivated indigo plants and prepared dye for over three decades.
Experimentation led to his rediscovery of traditional jjock-yeomsaek processes, and he has since become the major exponent of the art in Korea.