Why does ultramarine pigment have an odor? Turquoise blue pigment is an ancient and vibrant blue pigment, as well as a common mineral pigment. Early turquoise came from ground lapis lazuli, which is a sodium aluminum sulfide silicate. In the West, its color symbolizes the Virgin Mary and has important religious significance. Due to the rarity of lapis lazuli, the price of ultramarine remained high until the 19th century when people innovatively invented artificially synthesized ultramarine

The main raw materials used in the production of Qunqing Blue pigment are kaolin, soda ash, and sulfur. The production process should be carried out in a closed kiln, and the kiln needs to discharge air first to prevent oxidation reaction of sulfur before reaching the reaction temperature. Then, the sulfur, clay, and sodium carbonate are heated to about 800 ℃. After maintaining a high temperature for a certain period of time, the initial chromophore can be formed. Then, the mixture is cooled and air is allowed to slowly enter the kiln to complete the oxidation process. This high-temperature processing process takes more than two weeks to complete. Therefore, for every ton of ultramarine produced, nearly one ton of sulfur dioxide is released. If the post-treatment is not perfect during production, it is inevitable that there will be free sulfur in the ultramarine blue pigment

The sulfur ion (S3-) in the chemical structure of ultramarine pigments is difficult to imagine that the sulfur element, which usually appears yellow, can also serve as a blue chromophore. However, in special valence states, sulfur ions are more abundant The spectral absorption caused by the orbital of electrons in the heart makes the ultramarine pigment appear beautiful and persistent Long lasting color

However, the discovery of the sulfur ion (S3-) chromophore was only the first step in the synthesis and production of ultramarine a step. The instability of chromophores makes them easily oxidized, forming sulfides that cannot be used as pigments. Therefore, in order to avoid chemical reactions of chromophores during the production process, they need to be placed in a cage like lattice structure made of kaolin