Ultramarine is a sulfur-containing compound of aluminum silicate. Its composition can be written as Na6Al4Si6S4O20. Ultramarine is a very bright and unique red light blue color. It has excellent heat resistance and can withstand a temperature of 350°C for 5 minutes in plastic processing. Its light fastness is very good, up to grade 7~8, and its dispersibility is also very good.

       Ultramarine blue is resistant to alkalis and many chemicals, but it is not resistant to acids. It is more transparent. Ultramarine is suitable for coloring various plastics such as polyethylene, polypropylene, polystyrene, ABS, nylon, polycarbonate, phenolic resin, and amino resin.

       Ultramarine is non-toxic. Extensive experiments have proved that the oral fatal dose to mice is greater than 1Og/kg. It can be used for coloring plastic products in contact with food, such as packaging containers for mineral water.

       Ultramarine blue is widely used in titanium dioxide carving white, and its dosage is between 0.1% and 1% of titanium dioxide, which can obtain milky white to blue-white and other tones. Ultramarine blue has a bright red light blue color, so royal blue can be obtained by matching with phthalocyanine blue in different proportions. Its disadvantages are poor tinting strength and light-shielding properties, and black lead sulfide may be formed when it interacts with lead-containing compounds. Therefore, phthalocyanine is commonly used in PVC. Blue instead of Ultramarine.