A mixture used in Japan for filling cracks and losses in lacquers. Kokuso is composes of urushi, baked sawdust, and flour (Webb 1998). The flour and water is made into a paste, the urushi is slowly added followed by the sawdust. Variations include the addition of nori urushi (rice flour and urushi) or chopped linen fibers (Webb 1998).
M.Webb, "Methods and Materials for Filling Losses on Lacquer Objects" JAIC, 37:117-33, 1998.