23/12/2019

Color stability test: Overview of “type” classifications

GRS Laboratories now offers color stability testing services at all laboratory locations

Color fading is a natural phenomenon observed in certain gemstones, particularly with orange to yellow sapphires. In most cases this phenomena is reversible and occurs when the sapphire is exposed to a certain type of light. The light sources emission energy will eventually induce a color-change, effectively reducing the yellow or orange component of that sapphire. For example an orangy-pink Padparadscha sapphire can change to a pink sapphire color. The original color can often be reinstated after exposure to a particular light source such as long-wave UV-light.

GRS has established four categories in which we divide the tested gemstones. After color stability testing has been performed, the observed results will be reported as follows on the GRS Gemstone Report:

Type 1: Color is stable
Comment on report: Color stability test applied. No indication of fading was observed. Post-testing exposure to UV- or sunlight will not increase the color saturation and/or cause a change in hue.

Type 2: Color unstable, submission in charged state
Comment on report: Color stability test applied with indication of orange and/or yellow component fading was observed. Post-testing increase of color saturation and/or change of hue by exposure to UV- or sunlight is possible.

Type 3: Color unstable, submission in uncharged state
Comment on report: Color stability test applied. No indication of fading was observed. Post-testing increase of color saturation and/or change of hue by exposure to UV- or sunlight is possible.

Type 4: Color unstable, submission in charged state, stone cannot be re-activated after fading
Comment on report: Color stability test applied with indication of fading was observed. Post-testing increase of color saturation and/or change of hue by exposure to UV- or sunlight is not possible.


News