Analysis of information sources in references of the Wikipedia article "Sokutai" in English language version.
The roots [of the plant] are collected and dried for two to three months to mature the color. While this occurs, the silk is pre-mordanted [...] the mordanting process involves repeated immersion of the cloth or yarn in the alum bath and drying over a two- or three-month period. To prepare the dyestuff, the gromwell roots are softened overnight in 60°[celsius] water and then pounded to release the dye. The silk is then repeatedly immersed in the bath, aired to allow more oxygen to penetrate the cloth and then steeped in the dye until the desired color is achieved. When the dyeing is completed the cloth is placed in dark storage for as long as a year while the color continues to mature.
The roots [of the plant] are collected and dried for two to three months to mature the color. While this occurs, the silk is pre-mordanted [...] the mordanting process involves repeated immersion of the cloth or yarn in the alum bath and drying over a two- or three-month period. To prepare the dyestuff, the gromwell roots are softened overnight in 60°[celsius] water and then pounded to release the dye. The silk is then repeatedly immersed in the bath, aired to allow more oxygen to penetrate the cloth and then steeped in the dye until the desired color is achieved. When the dyeing is completed the cloth is placed in dark storage for as long as a year while the color continues to mature.
