Light resistance test for pearls

Abstract

In jewelry market of these days, we can often see the pearls sold as “Untoned” or “Natural Blue”, emphasizing not to be tinted and colour-treated.

On the other hand, colour-treated pearls with unusual colours such as “Lavender”, “Pistachio” and “Chocola” are sold, by which consumer’s choice was supposed to be expanded to enjoy inexperienced colours.

However, regarding to colour-treatment with dye, the effects obtained by the treatment may be unstable. The main factors for faded colour and decreased luster must be sweat, abrasion, light and heat. Especially, ultraviolet is a frequent high-risk factor faced always in daily life.

Then, I performed light resistance tests for various coloured pearls generally seen in the market to inspect the durability in pearl colours and change of appearance against Ultraviolet.