非彩色背景对铝系列紫色—红色系石榴石颜色的影响

The Effect of Non-color Background on the Color of Purple-red Garnet in Pyralspite Series

选取34颗紫色—红色系石榴石,采用紫外—可见光分光光度计、X射线荧光光谱仪、爱色丽分光光度计、Munsell中性灰色背景对样品进行观察与测试。经测试确定了此次实验所选取的紫色—红色系石榴石均属于铁铝榴石和镁铝榴石之间的过渡品种;紫外可见光光谱显示,Cr导致了红区692nm处的吸收,Fe导致了黄区575nm强吸收带、绿区527nm和蓝区504nm弱吸收带。基于CIE 1976 L~*a~*b~*均匀色空间,依次转换Munsell非彩色背景N1—N9,研究不同明度的非彩色背景对石榴石颜色三要素的影响,发现随着非彩色背景明度的升高,石榴石颜色的明度和彩度均逐渐升高。方差分析结果表明,不同明度的非彩色背景对石榴石颜色的明度、彩度有极显著影响,对色调角没有显著影响。采用K-means快速聚类,将石榴石按色调角划分为三类,在转换N1—N4背景时,色调角降低,转换N5—N9背景时色调角升高,向红色、橙色区转移。为使石榴石展现更高的明度和彩度,可将石榴石放置于高明度的背景环境中。

Thirty-four gem-quality garnet samples were studied using UV-Vis spectrophotometer, X-ray fluorescence spectrometer, X-Rite spectrophotometer and Munsell neutral gray backgrounds. The purple-red garnets selected in this experiment belong to the transition variety between pyrope and almandine;The UV-Vis spectrum shows that Cr leads to absorption at 692 nm in the red region, Fe leads to absorption band at 575 nm in the yellow region, 527 nm in the green region and 504 nm in the blue region. Based on CIE 1976 L~*a~*b~* uniform color space, the Munsell non-color background N1-N9 was converted in turn to study the influence of different lightness of non-color background on the three elements of garnet color. It is found that the lightness and chroma of garnet color gradually increased with the increase of the lightness of non-color background. The results of variance analysis show that the non-color background with different lightness has a very significant effect on the lightness and chroma of garnet color, but has no significant effect on the hue angle. Using K-means fast clustering, garnet samples are divided into three categories according to hue angle. When the N1-N4 background is converted, the hue angle decreases. When the N5-N9 background is converted, the hue angle increases, and the garnet hue is transferred to the red and orange areas. In order to make the garnet show higher brightness and more saturated color, it should be placed in a high lightness background environment.