Feature of Sumac

The insect-induced galls that form on the Chinese sumac (Rhus javanica) are known as gobōshi (gallnuts), and have been traditionally used for both dyeing and medicinal purposes. They have been valued for their therapeutic properties, particularly as antitussive, anti-inflammatory, and dermatological agents. During the Heian period (794–1185), gobōshi was employed to produce black dyes and served as a key ingredient in ohaguro, the traditional practice of tooth blackening. These galls are rich in tannins and are used to dye a variety of subdued hues, including fuji-nezumi (wisteria gray), ao-kaiiro (bluish gray), and murasaki-nezumi (purple gray).

Chanese smac

About Sumac dye

Gobōshi (gallnuts) is rich in tannic acid, which reacts with iron to produce a dark purplish-black hue. In addition, alum mordanting in gobōshi dyeing results in a pale color, with minimal change in the fabric’s hue, and has traditionally been used as a pre-dyeing step for achieving deeper shades. This dyeing process allows for the creation of various muted tones, including kara-gobōshi (empty gobōshi color), fuji-nezumi (wisteria gray), ao-kaiiro (bluish gray), and murasaki-nezumi (purple gray), which are all variations of grayish hues tinged with purple or ink-like tones.

Method of dyeing

The dyeing process employs a mordanting technique. Gobōshi is placed in a stainless steel pot and decocted. After approximately 15 minutes, the liquid is filtered through cloth, and the extraction process is repeated 3 to 4 more times to obtain additional dye liquor.
Due to the high tannic acid content, the dye exhibits excellent substantivity, and thus, pre-mordanting with substances such as soybean milk is not necessary for plant fibers. Repeated cycles of dyeing and post-mordanting with iron (ferrous sulfate) result in progressively deeper shades, eventually yielding a near-black color.

Color defernce by mordant