Jianzhan is a Chinese teacup known for its unique glaze, a must-have for tea lovers or art collectors. The glaze pattern on this Jianzhan is often referred to as "blooming". Jianzhan is 100% safe for consumption, but should not be used in microwaves due to the high iron content of the clay.The high firing temperature (about 1300 degrees Celsius), strong reducing properties, high iron content and crystalline pattern all contribute to the high failure rate of Jianzhan. Jianzhan with such a uniform and beautiful glaze is very rare.