Gas Bubble Characteristic of Translucent to Opaque Amber and Its Relationship to Quality Assessment

Amber is a kind of translucent to opaque and milky appearance, which is caused by reflection and scattering of light induced by the abundant minutegas bubbles in amber. In this paper, the authors used scanning electron microscope (SEM) to observe the size and distribution to measure the diameter and to count the number in per unit area and area ration of the bubbles in a variety of amber. The resulte is following: (1) The gas bubbles are caused by the volatile matter interior of amber and they have round shape and uniformly distribute in the laminated structure. Their diameter ranges from 100 nm to 15 μm and their density is from hundreds to thousands per unit area (mm²), and even reaches millionsper unit area (mm²) in white opaque amber. (2) The density of the gas bubbles in the SEM image is positively related to the opacity. Larger area occupied by the gas bubbles leads to less transparent appearance. (3) The apparent visual smoothness and tenderness degree of amber is found to be negative correlated to the diameter of gas bubbles. Smaller gas bubbles build up better and smoother texture. Our study contributes to the development of the translucent to opaque amber texture assessment system.