After refining, black or red lacquer is filtered through cloth or washi paper before being applied with a special brush. Extreme care is required to ensure that fine airborne particles of dust and dirt do not get into the lacquer. Unlike synthetic paints, lacquer (urushi), which is a natural tree sap, hardens in a moist environment, so careful attention must also be paid to maintaining proper levels of temperature and humidity. Yamanaka lacquerware is known for unique lacquering techniques such as tamenuri, hananuri, and kiriaiguchi. More than 80 percent of all tea caddies used in the tea ceremony are Yamanaka lacquerware.