When dyeing, the lenses must be classified according to the material. The most commonly used method for resin lenses is the immersion method. The plastic lens is immersed in a high-temperature dye solution to dye the lens with various colors. Before dyeing, put the lens in a solution containing surfactant and alcohol for pretreatment, and then immerse the lens in a pool filled with water and color pigments. When the liquid temperature is as high as 97°C, the molecular network structure of the plastic will expand at high temperatures, and the colored particles floating in the water can penetrate into the surface of the plastic lens. In the subsequent cooling process, the surface structure of the lens is closed again, so that the color pigment is enclosed in the material.
Although glass lenses are not common anymore, occasionally, we will receive prescriptions for staining glass lenses. This dyeing is mainly colored by vaporization. The lens is heated to 300°C, and then one side of the lens is steamed with the mixture of light-absorbing metal oxides. This process can evenly steam the color on the entire surface, but there are few dyeing varieties of this kind of lens.