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Analysis of Cima PaintingOpt

Analysis of Cima PaintingOpt - Gesso Underpaint LMA on the...

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Investigating Cima In 1504 Cima da Conegliano finished an altarpiece “the Incredulity of St Thomas”. After suffering damage it was bought by the National Gallery in 1861 but in 1969 it required major restoration. To help with the restoration tests were carried out: 100’s of free ppt’s from www.pptpoint.com library
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The Painting
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Reflectance Spectra A B Use your data sheet to identify the pigments used in each area. What are the chemical substances What colour would you expect each to appear ? 400 450 500 550 600 650 700 750 0 50 400 450 500 550 600 650 700 750 0 10 20 30 40 50 60 Wavelength /nm % reflection
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Does this help ?
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Position of samples A and B
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Now look at St Peter's Mantle
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L aser M icrospectral A nalysis Laser light Electrodes Spectrometer Paint Sample
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A fragment of paint was cross sectioned
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Unformatted text preview: Gesso Underpaint LMA on the upper layer gave lines at 228.8 nm and 235.0 nm . Identify the element present and hence the pigments used. Identification of oils (1) A sample of paint is hydrolysed to give the potassium salts of the saturated fatty acids OH OH OH O O O O O O O O O O O O K + K + K + KOH(aq) + Identification of oils (2) The potassium salts are converted to the free acids. And then to the methyl esters. O O K + O OH H Cl O OH O O CH 3 CH 2 N 2 So what medium did Cima use ? ● glc shows the proportions of saturated esters. ● What happened to the unsaturated acids ? ● For Cima's painting palmitate/stearate = 76/54 = 1.4 ● What medium has this ratio ?...
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