Dokoppi - Kunugi (Sawtooth Oak barkchips)

Amount used
Same weight as the dough 

Summary
The acorn part of the sawtooth oak, a deciduous tree widely distributed in the Honshu, Shikoku, Chugoku, and Kyushu regions, is called dokoppi. Both the umbrella part (kudo) and the acorn itself are dyed wild golden yellow, so it is often used for under-dyeing. In ancient times, it was called "tsurubami" (acorn) and was used as a dyeing material to dye blackish brown.

Dyeing method
Boil in boiling water at about 80℃.