Their colors usually fall in the spectrum between lavender gray and plum green. Sometimes though, they turn out brown or yellow. All these colors depend on temperature changes during the two-day firing — a process described by local craftsmen as "a song of clay and fire".
The traditional firing techniques of Longquan celadon pottery, which dates back further than 1,600 years, was included on UNESCO's Intangible Cultural Heritage of Humanity List in 2009.