Environment Effect on Colour of Dyed Pearl and Preliminary Modification of Nano-TiO₂

In order to solve the problems of fading and corrosion of dyed pearls in practical application,strenuous tests of ultraviolet ray irradiation and man-made sweat are carried out. The changes of the colour and luster of the samples are tested by using JEY-PS (China). The results indicate that the ultraviolet rays and man-made sweat have the direct effect on the dye. Rosy red and orange dyed pearl samples begin to fade respectively in 12 h and 36 h by ultraviolet ray irradiation and erode respectively in 90 min and 30 min by man-made sweat. By using Nano-TiO₂ modification technology, uvio-resistant property of the dyed pearl samples is 3 or 4 times higher than that of original dyed pearls, and corrosion-resistant property of the dyed samples is 10 times higher than that of original dyed pearls.