Limewashed mural paintings as seen by VIS-IR reflectography

Abstract

Near-Infrared (NIR) reflectography is a well-established technique for painting diagnostics, offering a fundamental contribution to the conservation of paintings. Since the '80s it has been routinely applied to study the execution technique of the author, as well as the presence of pentimenti, retouches, integrations or underdrawing. In the last decades IR reflectography has been extended to the visible (VIS) spectral range, providing information about the pigment composition. Up to now the multispectral analysis is still applied at an experimental level, as the processing of the image set is not straightforward. Rarely multispectral VIS-IR application has been applied to frescos, probably due to the lack, in most cases, of a scattering background. In this work we present the results provided by a multispectral scanning device based on single sensor acquisition, working in the 380-2500 nm spectral range, that is a laboratory prototype specifically built for research-grade imaging. The technique have been applied on a mock up simulating a mural painting substrate where an underdrawing, made of either carbon or iron-gall ink, was covered by different surface layers of limewash, the so-called scialbo.

Morphological Structural Element Optimization for Automatic Line Characterization of Ink Drawings

“…As the basic technique of ink landscape, the "hook," "chap," "dye," and "point" are also made up of a thousand different combinations of lines [23]. From this, we can see that ink lines are the soul of ink painting and the basic steps of ink painting [24]. erefore, this paper will discover the rendering algorithm of ink and landscape painting based on images, starting from ink lines [25].…”

Revealing Underdrawings in Wall Paintings of Complex Stratigraphy with a Novel Reflectance Photoacoustic Imaging Prototype

“…The charcoal line edges appear slightly blurred which is probably attributable to the fresco execution method causing the dispersion of black pigment particles, as best revealed by PA image in Figure 6D and by NIR image at 1830 nm in Figure 6F. The best NIR result is observed at 1830 nm (Figure 6F), where limewash is known to show the highest transparency [20].…”

“…Many studies can be found in the literature on NIR imaging used to reveal underdrawings in fresco and secco wall paintings underneath retouched areas, while little can be found on deeper concealed features (covered by limewash, concealing mortar layers etc.). A dedicated study has already proven the efficiency of NIR imaging to reveal iron-gall ink and carbon-based sketches on mock-ups with a limewash layer up to 200 µm thick, by selecting the most appropriate wavelength [20].…”

Synchronized Hardware-Registered VIS-NIR Imaging Spectroscopy and 3D Sensing on a Fresco by Botticelli

“…While the first instruments for IR reflectography collected the radiation in a single, broad spectral range [ 1 ], the method gradually evolved, starting from the mid 1990’s, into the multi/hyper spectral (MS/HS) modality, derived from Earth remote sensing techniques [ 2 ]. The great potential of MS/HS reflectance imaging spectroscopy (RIS) in the analysis of artworks has been recognized by the heritage science community, today including a large number of research groups active in this field [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. A detailed account of the evolution and progress, as well as of the fundamental physical principles of RIS and systems involved, is provided in a recent review [ 19 ].…”