After six years of continuous research and development, we have selected foreign special raw materials and verified them with the help of the users. We have introduced coating that change color when exposed to water, which is suitable for plastics, metals, paper, non-woven fabrics and other substrates, can use gravure, flexography, roll coating, brush coating, spraying and other construction methods. Coating can be self-drying or baked drying. The dry coating is yellow and turns blue when exposed to water. Optional reversible or irreversible discoloration. Reversible blue turns yellow after drying; irreversible blue remains blue after drying.