Urushi (漆 [urushi])

Urushi is natural lacquer made from the sap of the lacquer tree, Toxicodendron vernicifluum. Unlike modern paint, it does not dry by simple solvent evaporation: it cures by enzymatic oxidation and polymerization in a warm, humid environment, usually inside a furo or muro.

Once cured, urushi forms a tough, chemically resistant film that can be built in thin layers, polished to high gloss, or used as an adhesive and binder for powders and pigments. Uncured urushi contains urushiol, the allergenic compound responsible for urushi rash, so careful skin and eye protection, clean tools, and disciplined handling are essential.