Origin: Huanglong Mountain, the original mine is greenish gray, which is the grease contained in the interlayer in the purple sand mud. It is beige after firing.
Kiln temperature: 1180 degrees.
Shrink ratio: about 12%.
Duan mud has low iron content, generally around 2%. If it is higher than 2%, the color is yellowish and dark. The color of sintered sludge in the oxidizing atmosphere changes from light yellow to red-yellow, deep yellow and yellow-brown