After undergoing the shimebata process, the silk threads are dyed using techigi (wheel plum) and mud, two resources unique to the natural environment of Amami. Techigi, which grow wild on the islands, are boiled in large cauldrons for two days. This boiling process releases a sharp, distinctive aroma that fills the entire workshop. The silk threads are then immersed in this dye bath and vigorously kneaded by hand. This procedure, involving multiple changes of the dye bath, is repeated 20 to 30 times to achieve the desired depth of color.
Approximately 600 kilograms of techigi are required for mud dyeing. The trees are harvested from the mountains, with their trunks broken down into chips and then boiled in cauldrons. During the summer, the harvested wood must be brewed within about two weeks to ensure it yields high-quality dye. The quality of the techigi is key to determining the final result of the mud dyeing process.
Afterward, the kasuri mushiro (woven patterned mats) are taken to a mud field for the mud dyeing process. Workers wade into the knee-deep mud, stirring the settled mud with their feet while adopting a half-crouched posture. They repeatedly knead and pound the mats with great force, ensuring the mud penetrates thoroughly. This labor-intensive process is far from easy, but it is essential to achieve the signature black color. The tannins from the techigi dye and the iron content in the mud undergo a chemical reaction during this step, creating the characteristic deep black of Oshima Tsumugi.
After finishing the mud-dyeing stage, the mats are rinsed in the river to remove the mud and are then returned to the techigi dye bath. This cycle of dyeing alternates between techigi and mud, repeated three to four times. In total, the dyeing process is conducted 70 to 100 times.
Unlike chemical dyes, which penetrate the fibers uniformly, mud dyeing forms dye layers in a ring-like formation around the threads. Repeated applications of mud dye produce a richness and depth of color that cannot be replicated by synthetic dyes. This laborious process results in Oshima Tsumugi’s unique, lustrous “black.”
As the dye is derived from natural materials, it evolves over time. After 30 to 40 years, the surface oxidizes, gradually transforming into a warm reddish-brown hue. This aging process is yet another alluring feature of mud-dyed textiles.
The mud fields of Amami Oshima are rich in iron and characterized by fine, smooth particles. These unique qualities are believed to be the reason mud dyeing originated exclusively in Amami Oshima. It is truly a miraculous dyeing technique born of the island’s exceptional soil.
In Tatsugo Town, a clay layer estimated to be about 1.5 million years old remains, providing ideal conditions for mud dyeing. As a result, this area became a hub for the craft. At its peak, there were 60 to 70 mud-dyeing workshops on Amami Oshima, but today, only a handful remain. Most of these workshops were historically concentrated in Tatsugo Town, further underscoring the suitability of the area’s soil for mud dyeing.