Post-Processing of VIS, NIR, and SWIR Multispectral Images of Paintings. New Discovery on the The Drunkenness of Noah, Painted by Andrea Sacchi, Stored at Palazzo Chigi (Ariccia, Rome)

IR Reflectography applied to the identification of hidden details of paintings is extremely useful for authentication purposes and for revealing technical hidden features. Recently, multispectral imaging has replaced traditional imaging techniques thanks to the possibility to select specific spectral ranges bringing out interesting details of the paintings. VIS−NIR−SWIR images of one of the The Drunkenness of Noah versions painted by Andrea Sacchi, acquired with a modified reflex and InGaAs cameras, are presented in this research. Starting from multispectral images we performed post-processing analysis, using visible and infrared false-color images and principal component analysis (PCA) in order to highlight pentimenti and underdrawings. Radiography was performed in some areas to better investigate the inner pictorial layers. This study represents the first published scientific investigation of The Drunkenness of Noah’s artistic production, painted by Andrea Sacchi.