About Urushi, a natural lacquer

More than just a tree…

Urushi is the sap of the urushi tree. It has strong adhesive properties and is used as a lacquering material that on hardening becomes extremely durable and produces a glossy finish. It has unique properties in that not only can it be used as a coating material to protect and preserve but also can also be used as an adhesive to form structures or as a refined decorative material. Various varieties can be found widely throughout Eastern Asia and it has been used in Japan for over nine thousand years.

The word ‘urushi’ is thought to have originated from the Japanese uruwashi or urumu which approximates to the English for fresh and vibrant gloss. When urushi hardens it is very resistant to both acids and alkalis and is durable enough to last several thousand years. Urushi vessels have been found in excavations that date from the Jomon period (8000 BC - 300 BC). There have even been cases reported where the original wooden base has completely rotted away but the original urushi coating has remained with its color and quality preserved. 

On the other hand urushi is also a very delicate substance. The quality of urushi changes depending on the time of day and year in which the urushi is taken from the tree and it is also affected by the method by which it is collected. Urushi is different from other coating materials in the way that it is dried. It contains a substance called urushiol which reacts with oxygen and hardens through a process of oxidative polymerization with the help of an enzyme. For this process to occur, a suitable temperature and level of humidity are both necessary. The drying process also proceeds gradually over a considerable length of time after the piece has been completed. Therefore a piece that has just been finished should be treated very carefully when it is first used. It can be used normally after the first yearthree months and after about three years of use the gloss fully matures and the piece can be said to have come of age.