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Investigating Cima

This article explores the restoration of Cima da Conegliano's altarpiece "The Incredulity of St. Thomas," initially acquired by the National Gallery in 1861 and requiring significant restoration in 1969. It details the methods used in restoration, including paint sample analysis through Laser Microspectral Analysis and the identification of pigments and oils. Notable findings include the investigation of chemical substances, the expected color appearance of pigments, and the evaluation of fatty acid esters to determine the medium employed by Cima, providing insights into the artist's techniques.

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Investigating Cima

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  1. 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: Investigating Cima

  2. The Painting

  3. 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 ?

  4. Does this help ?

  5. Position of samples A and B

  6. Now look at St Peter's Mantle

  7. Electrodes Laser Microspectral Analysis Laser light Paint Sample Spectrometer

  8. A fragment of paint was cross sectioned LMA on the upper layer gave lines at 228.8 nm and 235.0 nm. Identify the element present and hence the pigments used.

  9. Identification of oils (1) A sample of paint is hydrolysed to give the potassium salts of the saturated fatty acids

  10. Identification of oils (2) The potassium salts are converted to the free acids. And then to the methyl esters.

  11. 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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