吶喊為挪威畫家愛德華·孟克的作品,其呼喊的「怪異」樣貌形象非常鮮明。903Please respect copyright.PENANAC4ohT0iARK903Please respect copyright.PENANAIk1aBKIp6o
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他本人在1893至1916年畫出多個版本,而其中一幅展示在孟克美術館(Munch Museum)的版本因多處黃色地方出現變白及脫落跡象關係(圖1的數字標記區域),自2006年起已甚少公開示人。903Please respect copyright.PENANAmfQfKSohTX
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作品現時正處於光線陰淡、攝氏18度、相對濕度約50%的環境備受保護。903Please respect copyright.PENANA2xcaRMkq9z
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(圖2)為了解箇中顏料變色及脫落的機制,有科學家對吶喊作品作出深入研究,並在近日發表文章講述得出的結果(Ref1)。903Please respect copyright.PENANAqiaAs3FSq7903Please respect copyright.PENANA9T2jKUs6CP
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Cadmium sulfide,為該時期常用作為黃色顏料的化學物。903Please respect copyright.PENANAtw555Q0Cb6
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同期的文森·梵谷 (Vincent van Gogh)、詹姆斯・恩索 (James Ensor)和亨利·馬諦斯(Henri Matisse)均有利用這種化學物所製成的顏料,而相關的作品亦有出現黃色顏料變白的現象。903Please respect copyright.PENANABN5EaibgAa
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該時期主要有兩種方式製作Cadmium sulfide,分別為Dry及Wet Method。903Please respect copyright.PENANAvs0pza7qZS
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Dry Method為以300°C至600°C及零氧氣的方式,加上大量硫元素(Sulphur)調配Cadmium sulfide的方式,得出的成品相對上較為純正。903Please respect copyright.PENANAm5hTi990wC
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Wet Method為將不同的化學物混合在一起(如圖中所示),再以沉澱的方式獲取固體Cadmium sulfide。903Please respect copyright.PENANAoY2Z1hbiZB
基於當時技術相對上不太先進,最終的產品會含有較多雜質及副產品。903Please respect copyright.PENANAHHSy6ES39B
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(圖3)科學家在文中嘗試挖取微量的吶喊畫碎粒,再利用各種技術檢測畫中的化學物成份。903Please respect copyright.PENANAeZpQ9iNZmB903Please respect copyright.PENANAhSflsljzao
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圖3中間的圖片,其紅點代表黃色顏料Cadmium sulfide的存在。903Please respect copyright.PENANAWYbEvBPpUP
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下方的圖片,其三種顏色的出現分別代表Wet Method的副產物。903Please respect copyright.PENANAE5OLt5ZhCd
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紅點:Cd(OH)Cl903Please respect copyright.PENANAu081cF6vuX
綠點:CdSO4903Please respect copyright.PENANAMF7LRfuwtg
藍點:CdCO3903Please respect copyright.PENANAsr1hX96GiX
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這三種副產物,在長久而來的知識中已被確認是顏料變色及脫落的兇手,與吶喊作品所出現的現象不謀而合。903Please respect copyright.PENANAHp2fDJ5qY4
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(圖4)為進一步了解顏料變色的現象,他們找來了吶喊畫同期帶有黃色顏料的作品(他們已7914數字命名樣本)。903Please respect copyright.PENANAbvQwbGTka2903Please respect copyright.PENANAgiO4O2vVJp
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拿取畫中碎片後,(圖4左方)他們同樣發現裡頭含有Wet Method的副產物(綠點)。903Please respect copyright.PENANA0eQ67mihDX
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為了解環境因素對於顏料變色的影響,他們對另一塊畫碎用上90 日相對濕度≥ 95%,攝氏為40°C,無光環境來模仿歲月的摧殘。903Please respect copyright.PENANAiePijEgomq
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他們發現得到Wet Method的副產物Cd(OH)Cl(綠點)數量大增且集中在一起,其目測得到黃色顏料變白的現象發生。903Please respect copyright.PENANA6glzQ2MnHE
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然而,用上用上90 日相對濕度=45%,攝氏為30°C,300W光源直接照射的環境來模仿歲月摧殘的話,則沒有感測得到Wet Method副產物的產生和顏料變色現象發生。903Please respect copyright.PENANADHkamxf7GV
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(圖5)另外,他們亦對愛德華·孟克那時期捐贈予館舍的顏料油作出檢測。903Please respect copyright.PENANAO2y2Fc3TWx903Please respect copyright.PENANAkOzH77f1TJ
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在畫紙塗上顏料油後,已能測量得到有一定程度份量的Wet Method副產物Cd(OH)Cl(左圖綠點)。903Please respect copyright.PENANAqfMRkvm2ID
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(右圖)用上90 日相對濕度≥ 95%,攝氏為40°C的方式摧殘後,綠點數量大增且集中在一起。903Please respect copyright.PENANAZxq3SgXD3X
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(圖6)換句話說,當時期以Wet Method製作的Cadmium sulfide顏料以及愛德華·孟克所使用的顏料油,乃是導致畫中黃色地方出現變白及有脫落跡象的元兇,而其變色的機制主要由相對濕度和溫度而非光線控制。903Please respect copyright.PENANASBbJOBhN8t903Please respect copyright.PENANAHu0ve7N8p7
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基於這發現,在相對濕度及溫度嚴密的控制下,吶喊他日將來也許會有機會可以再度長期公開示人。903Please respect copyright.PENANAF5FoKCCneS
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Ref1:https://advances.sciencemag.org/content/6/20/eaay3514903Please respect copyright.PENANAdMNydzJck9