It has been regarded as an important object since the Jomon period (14,000 B.C. - 3rd~5th century B.C.) and has been handed down to the present day as part of the uniquely Japanese culture. The transparent luster of urushi ware is irreplaceable, and its moist texture enriches the hearts of those who use it.

Lacquer tree

The milky white sap extracted from lacquer tree, which grows wild widely in Asia, is refined and used as a paint or adhesive. After the sap is filtered and the barks are removed, it is called “kiurushi”. This is then refined to produce black urushi, transparent urushi, etc. The transparent luster of urushi ware is unique, and this transparency gives it a beauty not found in other paints.
Lacquer trees grow in Japan, China, and Southeast Asia. In the past, purified urushi sap was produced in various regions of Japan, but today, more than 90% of the urushi sap used in Japan is imported from China. Japanese urushi sap is rare and expensive (about five times more expensive than Chinese one), so it is mainly used for repairing important shrines and temples.
Since Chinese, Korean, and Japanese lacquer trees have the same DNA, their properties are quite similar. However, depending on the country and region of origin, and depending on the age and time of collection, the composition of urushi sap (resin content called urushiol, moisture, rubbery material, enzymes, etc.) differs, and the viscosity and speed of drying differ. By understanding these properties and combining different types of urushi, we can use the right type of it for the purpose of use.

Properties

Although urushi is well known as a paint, it is also used as an adhesive to make kanshitsu (base) or to attach gold powder or thin shells, taking advantage of its hardening property. This adhesive strength is used to bond ceramics together in kintsugi (metal-joining).

When urushi is purified, it becomes a clear candy color, so it can be mixed with pigments to create any colored urushi, just like paint. As time passes after hardening, the color of urushi becomes almost transparent and the pigment gradually becomes stronger. However, it is difficult to produce pure white colored urushi, because even when mixed with pure white pigments, the color will become brownish. If the urushi dries quickly, the brown color of the urushi itself becomes darker, and if it dries slowly, the urushi becomes more translucent, so colored urushi would be better to harden slowly.

Hardening mechanism

Generally, the word "dry" is associated with an idea of moisture evaporating into the air, but urushi is the opposite. It dries by taking in moisture from the air. Therefore, to be precise, urushi is not said to "dry" but to "harden".
Hardening of urushi means that the enzyme (laccase) in the component reacts by taking in oxygen in the moisture, causing urushiol to change from a liquid to a solid.
The best conditions for urushi to harden are a temperature of 25~30 degrees Celsius and a humidity of 70%, and it hardens particularly quickly during the rainy season. To harden urushi in other seasons as well, a hardening rack for urushi called "furo/muro" is used. This is like a wooden shelf with slide doors, and moisture is applied directly to the interior walls, or a wet cloth or a water-filled tray is placed at the bottom to control humidity.

Cardboard or plastic case can be substituted, but it is more difficult to control humidity compared to wood. A "karamuro" hardening room, which does not provide humidity, is also necessary for when you want to harden taking for a longer time. I can turned a piece upside down by hand in dry muro. If a piece is not dried upside down, urushi often accumulates in the four corners of the box and shrinks.
If a piece is dried slowly, brush marks will disappear, but urushi on the sides will drip downwards. To prevent this, it is necessary to rotate the piece every few hours. If urushi is applied thinly, it is not necessary to do it, but it may be necessary under certain circumstances.

Care of urushi (lacquer) wares

The following are basic care instructions for urushi wares in general, but appropriate care instructions may vary depending on the actual type and the condition of the ware. Please refer to an instruction manual with the product.

I wrote these precautions so that you can use urushi wares as long and as beautifully as possible. However, urushi wares are inherently robust, so please do not be too nervous about using them for everyday use.

2024.05.14
2024.11.28