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。874Please respect copyright.PENANA5lbSz49wTb874Please respect copyright.PENANAAo7Cq2mjqq
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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。874Please respect copyright.PENANAXruh66g0SA
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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。874Please respect copyright.PENANAbjMx2pMaJT
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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)。874Please respect copyright.PENANAFE2S3FDUYT874Please respect copyright.PENANAz55K6KNrYz
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Cadmium sulfide,為該時期常用作為黃色顏料的化學物。874Please respect copyright.PENANAWJ3MlW2h5S
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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。874Please respect copyright.PENANADbAaOOVT98
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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。874Please respect copyright.PENANAfa6qohbXfR
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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。874Please respect copyright.PENANA6GT9PthtFY
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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。874Please respect copyright.PENANAlp0eCNVpXs
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。874Please respect copyright.PENANAm2Vsk5rwdL
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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。874Please respect copyright.PENANAGKCtaRtdxZ874Please respect copyright.PENANAJ9a6Mk8i1V
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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。874Please respect copyright.PENANAyWG8HZ7jg6
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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。874Please respect copyright.PENANAxmiKGQG9oJ
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紅點:Cd(OH)Cl874Please respect copyright.PENANAfxckjHW0Lx
綠點:CdSO4874Please respect copyright.PENANAMHjFK0egVX
藍點:CdCO3874Please respect copyright.PENANAyrc3bXrUxR
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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。874Please respect copyright.PENANA4zfaBaI20O
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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)。874Please respect copyright.PENANALLtBDk5Ia9874Please respect copyright.PENANA9Op2vJtoyX
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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)。874Please respect copyright.PENANAX7xgBcpGBF
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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。874Please respect copyright.PENANA7h7DeDxrXK
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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。874Please respect copyright.PENANALLvkeDzAhG
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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。874Please respect copyright.PENANA2kNxe5dX0N
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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。874Please respect copyright.PENANASEDrO92tun874Please respect copyright.PENANAUkv55kPmls
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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)。874Please respect copyright.PENANAIYeLnBdm18
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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。874Please respect copyright.PENANAS2ScN0EO17
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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。874Please respect copyright.PENANAUONlixwTgP874Please respect copyright.PENANALBasjmQEjb
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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。874Please respect copyright.PENANA70QmdQoU2W
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Ref1:https://advances.sciencemag.org/content/6/20/eaay3514874Please respect copyright.PENANAV9TGNCPDcs