In 1970, Japanese scholars studied the phase diagram of iron oxide microcrystalline formation, which laid a theoretical foundation for the preparation method of iron oxide yellow crystal seed. According to the research results, iron yellow crystal seeds can be formed under acidic or alkaline conditions. Because iron yellow is a crystal structure, in order to crystallize into pigment particles, it must first form crystal nucleus and become crystal seed, and then the crystal nucleus grows into iron yellow. Otherwise, only thin and dim color paste can be obtained, which does not have pigment properties. Acid process can be divided into iron sheet process and drop addition process.

All samples (n = 6) were irradiated in a 96 well plate using an LED panel on top for 3 and 6 h before analysis. An identical set of samples were kept in the dark as controls. The temperature was checked and did not go over 37 °C. The intensity of light was also measured and was constant at 19,500.10 lux. (43.33 W in 0.2 m²), about 5 times less than actual solar light intensity on Earth's surface Therefore, these findings are indicative of even greater danger in real life.