Physical–Chemical Characterisation of Leather from Corami Wall Hangings of Chigi Palace Using Non-destructive and Micro-Destructive Techniques

In this study, the results of a campaign of measurements by non-destructive and micro-destructive techniques on gilt and painted leather hangings from Chigi Palace (Ariccia, Italy) are reported. Both in-situ and laboratory analyses were performed to draw a comprehensive description of the manufacturing of leather, the support of such a delicate and complex sandwich artifact. The wall hangings in gilt, painted and embossed leather (in Italian, corami, cuoi d'oro or cuoridoro) are luxurious decorations used all over Europe between the sixteenth and eighteenth century. Despite this widespread use, most of them have disappeared. Those preserved at Chigi Palace, dating back to the seventeenth century, are therefore very important for understanding the Italian technique of corami. Although the leather support of the decorative layers is essential for corami’s conservation, its characterization and diagnostic are still a challenge. An integrated assessment procedure as a trustworthy, non-destructive, or minimally destructive tool for discovering more about the tanning and dying of leather was developed based on XRF, ATR-FTIR spectroscopy, and solid state 13C CP-MAS and 27Al NMR spectroscopy. The results showed that the leather used for the Chigi Palace wall hangings was made from goatskin using sumac tannin and red dyed with a brazilwood extract obtained in accordance with medieval recipes that include alum as a mordant and chalk/gypsum and white lead as extenders.