Imagine Van Gogh’s paintings of yellow sunflowers. Now imagine the flowers brown. Eh, not so good. Sadly, we may someday see what that would look like. Because the bright yellow paints on the canvas are slowly turning muddy. Now, an international team of scientists has ___1___ the chemical reaction that ___2___—the first step toward stopping it. Their findings appear in the journal Analytical Chemistry.
Van Gogh’s use of strong bright colors to convey mood and emotion ___3___ in art history. And his Sunflower series wouldn’t be the same without the vibrant “chrome yellow” pigment that was new at the time. But ___4___.

To find out why, researchers used sophisticated x-ray analyses to determine the exact chemical composition of the paint as it browns. First, they exposed three tubes of chrome yellow to UV radiation until one turned a chocolate color. Analyzing that sample, they identified specific changes in the paint’s chromium compounds. They then found the same chemical signature in the darkened areas of two van Gogh paintings. Until a chemical ___5___ is found, the researchers have some ironic advice: keep sunlight away from van Gogh’s sunflowers.
【视听版科学小组荣誉出品】
pinpointed drives this degradation marks a major milestone this color darkens when exposed to the sun antidote
大家先想象一下梵高画的《向日葵》，再试着想象一下那一朵朵向日葵变成褐色。额……貌似画面不太美妙嘛。虽然这是想象的画面，不过悲剧的是，想象可能即将成为现实，因为画布上金黄色的颜料慢慢变暗了。日前，一支国际科学家团队精确找到了引起这一变化的化学反应——这是防止画作继续褪色的第一步。研究发现刊登在《分析化学》上。 梵高以强烈的亮色传情的作画方式被誉为艺术长河中的里程碑。而少了当时新潮的一抹艳丽铬黄，定没有《向日葵》系列作品如此瞩目的成绩，但这种铬黄暴露在光线下就会暗淡。 为找出原因，研究人员用精密X射线分析仪测定了变成褐色颜料的精确化学成分。首先，研究人员将3管铬黄颜料暴露在紫外线下照射，直至有一管颜料变成巧克力色。分析了该管颜料后，研究人员发现了颜料中铬化合物的具体变化，继而他们又再梵高两幅画作暗色处与其相同的化学标记。在找到化学方法解决这一问题之前，研究人员提出了一个颇为讽刺的建议：别让梵高的《向日葵》晒着太阳~