Although it is widely known that the foundation color gradually changes over time after applying the makeup, no scientific clues are available, thereby remaining the “darkening” phenomenon equivocal. This study measured the discoloration of liquid foundations and suggested indices to describe the discoloration over time. Four liquid foundations were applied to opacity charts with a thickness of 100 μm, the surface color was obtained using a non‐contact spectrophotometer, and reported in the CIE 1976 L*a*b* color space. A long‐term measurement for 24 hours was conducted in that the initial 2 hours were measured with a 60‐second interval. The discoloration was observed as the decrease of both lightness and hue angle (h* of CIE L*C*h*) of liquid foundation over time. Different degrees and speed of color change were observed across the four foundations. Also, the discoloration was tested on three healthy human skins in 2‐hour intervals in repeated measurements. Positive correlations in changes of lightness and hue were found among the opacity charts and human skin. Furthermore, the study suggests indices, “Dt” and “TΔE” to describe the quantitative amount of discoloration over time and time duration of discoloration, respectively.

中文翻译：

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测量和描述粉底液的变色

尽管众所周知，在使用化妆品后，粉底颜色会随着时间的推移而逐渐变化，但没有科学的线索，从而使“变暗”现象变得模棱两可。这项研究测量了粉底液的变色，并提出了描述随时间变色的指标。将四个粉底液应用于厚度为100μm的不透明度图表中，使用非接触式分光光度计获得表面颜色，并在CIE 1976 L * a * b *颜色空间中进行报告。进行了24小时的长期测量，因为最初的2小时以60秒的间隔进行了测量。随着亮度和色相角（c *的h *L * C * h *）随着时间的流逝。在四个基础上观察到不同程度和不同的颜色变化速度。另外，在两次重复测量中，每隔2小时在3个人的健康皮肤上测试了变色。在不透明度表和人体皮肤之间发现亮度和色度变化呈正相关。此外，研究表明指数，“申”和“ Ť Δ é ”来描述变色的定量量随着时间的推移而变色的持续时间，分别。