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Before starting the restoration of an artwork, good practice involves the evaluation of the item healthiness possibly carried out through non-invasive techniques. In the specific case of painting inspection, hyper- and multi- spectral techniques are commonly used to analyze the outer layers (varnish, pictorial, and drawing), while X-ray, tomography, and many others can be employed to investigate its inner structure. Although highly desirable, a single technique providing all the information about a painting is still not available. Thus, it is of great interest to define the analysis’ protocols that could optimally exploit the complementarities of a minimal set of techniques. To this aim, the present paper shows the combined use of the hypercolorimetric multispectral imaging and pulse-compression thermography on a 15th century wall painting attributed to the Italian artist Antonio del Massaro, also known as Pastura, representing the Madonna with the Child and the Saints Jerome and Francis. The capabilities and the complementarities of the two techniques, whose information can also be fused through post-processing, are illustrated in detail in this paper. In addition, a false-colour imaging approach is proposed to improve the readability and analysis of the thermography results.

Some paintings may have hidden depictions beneath the visible surface, which can provide valuable insights into the artist’s creative process and the genesis of the artwork. Studies have shown that these covered paintings can be revealed through image-based techniques and integrated data processing. This study analyzes an oil painting by Beceri from the mid-16th century depicting the Holy Family, owned by the Uffizi Galleries. During the analysis of the materials, we discovered evidence of pictorial layers beneath the visible scene. To uncover the hidden figuration, we applied a multimodal approach that included microprofilometry, reflectance imaging spectroscopy, macro X-ray fluorescence, and optical coherence tomography. We analyzed the brushstrokes of the hidden painting, visualized the underdrawing, located the painted areas beneath the outermost painting, and quantified the thicknesses of the pictorial layers. The pigments used for the underpainting were identified through cross-analysis of X-ray fluorescence and spectral correlation maps. The underlying pictorial subject, Leda and the Swan, appears to be inspired by a long-lost and replicated work by Michelangelo. This information places Beceri and his production in a more defined context.

Since infrared reflectography was first applied in the 1960s to visualize the underdrawings of ancient paintings, several devices and scanning techniques were successfully proposed both as prototypes and commercial instruments. In fact, because of the sensors’ small dimension, typically ranging from 0.1 to 0.3 megapixels, scanning is always required. Point, line, and image scanners are all viable options to obtain an infrared image of the painting with adequate spatial resolution. This paper presents a newly developed, tailormade scanning system based on an InGaAs camera equipped with a catadioptric long-focus lens in a fixed position, enabling all movements to occur by means of a rotating mirror and precision step motors. Given the specific design of this system, as the mirror rotates, refocus of the lens is necessary and it is made possible by an autofocus system involving a laser distance meter and a motorized lens. The system proved to be lightweight, low cost, easily portable, and suitable for the examination of large-scale painting surfaces by providing high-resolution reflectograms. Furthermore, high-resolution images at different wavelengths can be obtained using band-pass filters. The in-situ analysis of a 16th-century panel painting is also discussed as a representative case study to demonstrate the effectiveness and reliability of the system described herein.

The examination with infrared reflectography of the Annunciation and the Adoration of the Shepherds , two panels from a dismembered altarpiece attributed to the mannerist painter Francisco João (doc. 1558–1595), revealed the first documented example in Portuguese painting of the overlapping of two underdrawing layouts, each with a different subject, in a single panel painting. The paintings were examined under visible radiation and infrared reflectography was used to investigate the underdrawing in terms of the materials, graphic layout and function. Results from a previous study on the ground layers and underdrawing materials of these paintings, obtained with the analysis of micro-samples with microscopic and spectroscopic techniques, were used in the context of this research. Infrared images revealed that the underdrawing of the Annunciation mostly corresponded to the painted image but that two subjects — Annunciation and Adoration — were drawn over the prepared surface of the panel depicting the Adoration . This discovery is the first example of this procedure in Portuguese painting. The comparison with a third panel attributed to the painter, depicting another version of the Annunciation , allowed for the discussion of relevant technical procedures such as the use of cartoons, the responsibility for each main stage of painting creation and the reality of labour conditions in a regional market. The results contributed with material evidence to the scarce information of archival nature about the working methods of Portuguese mannerist painters.

The exhibition “The Ladies of Art”, held at the Palazzo Reale in Milan in 2021, focused on the history of women artists during the 16th and 17th centuries. As part of the exhibition, a series of diagnostic analyses have been carried out on two paintings, thanks to the collaboration of several research institutions. The considered artworks consist of two paintings on parchments, realized by Giovanna Garzoni at the Savoy Court in the 17th century. Diagnostic analyses were performed using different, complementary, and non-invasive techniques: high-resolution multiband imaging, hyperspectral imaging, optical microscopy, X-ray fluorescence, and FORS spectrometry, combined with advanced post-processing techniques, in order to map and distinguish the pigments and the underdrawing of both the paintings. This research is the first conducted on these paintings and one of the few on the entire works of this important miniaturist. The results showed an incredibly meticulous painting technique, with a detailed metal point underdrawing and painstaking brushstrokes to describe the details with a high degree of realism. Precious materials, such as gold and lapislazuli, were identified and mapped. The findings of this work represent a new contribution of knowledge, which helps to lessen the lack of information for systematic studies on the artistic production of G. Garzoni.

The possibility of using the electron paramagnetic resonance (EPR) mobile universal surface explorer (MOUSE) to study underpaintings is validated. The depth sensitivity of the EPR MOUSE is measured using an EPR standard, and is verified using three paramagnetic pigments in an acrylic binder under opaque acrylic layers of titanium white and lead white. The ability to distinguish and identify two layers of EPR signal-bearing pigments is shown using pairwise sets of ultramarine, Egyptian, and Han blue pigments in an acrylic binder. And finally, the spatial imaging capability is demonstrated using a printed design of magnetite black covered with a solid second layer of the pigment. These studies demonstrate that EPR spectroscopy with the EPR MOUSE is a viable method for studying paramagnetic and ferrimagnetic underlayers of pigments.

Until today, iron gall ink is classified as an exceptional underdrawing material for paintings. Its study and definite identification is usually based on invasive analysis. This article presents a new non-destructive approach using micro-X-ray fluorescence scanning (MA-XRF), LED-excited IRR (LEDE-IRR) based on a narrow wavelength-range of infrared radiation (IR) for illumination and stereomicroscopy for studying and visualising iron gall ink underdrawings. To assess possibilities and limits of these analytical techniques, the approach was tested on panel paintings by Hans Holbein the Elder and Giovanni Battista Cima da Conegliano. Results are compared to invasive examinations on cross-sections using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). The holistic setup could successfully visualise iron gall ink underdrawings, allowing to harness the formerly invisible underdrawing lines for interdisciplinary studies.

Reconstructions were used as a tool to investigate the use of charcoal and black stone as underdrawing materials in sixteenth century panel paintings with white or off-white preparatory layers. Research was based on the examination of a group of sixteenth century panel paintings by the Portuguese Mannerist painter Francisco João (doc. 1558–1595) and his workshop. Analysis of the original underdrawing material in cross-sections, using microscopic and spectroscopic techniques was not always conclusive. Based on materials thought to be employed by Francisco João and on data collected from sixteenth and seventeenth century European technical treatises along with published analytical studies of panel paintings with white or off-white preparatory layers from this period, reconstructions were performed using charcoal (untreated and oiled—as described in contemporary literature) and natural black stone over different preparatory surfaces. Microscopic analyses of cross-sections from reconstructions were made to assist the discussion of the behaviour of the dry underdrawing media within the paint structure. Results revealed that whereas charcoal could be easily removed if drawn directly over gesso, it would remain fixed when drawn over a ground treated with an oil-based intermediate layer, even when the latter was completely dry to the touch. The persistence of a charcoal drawing when applied over oil challenged the widely disseminated assumption that naturally occurring black stone, which makes a permanent mark, had been employed more frequently than charcoal since the latter appeared to be easily disturbed and hence transitory. The very lengthy curing time for a drying oil could be responsible for fixing the friable media. Reconstructions further showed that oiled charcoal is easily prepared and agreeable to use on any type of surface, where it remains without smudging. Finally, research suggests that the painter’s choice of underdrawing material is closely dependent on the nature of the binder of intermediate layers and on the position of the underdrawing layout within the paint structure.

Visible-to-near-infrared reflectance imaging spectroscopy (417-2500 nm), the collection of hundreds of images in contiguous narrow spectral bands calibrated to reflectance, was employed to characterize drawing materials in Ballet Scene, a large-scale pastel on tracing paper by Edgar Degas. The spectral range from 417 to 950 nm proved useful in identifying and mapping the complex pigment application. The near-infrared (NIR) range from 962 to 2500 nm allowed visualization of underdrawing below multiple layers of pastel and fixative that depict positions of the dancers' bodies and costumes in the pastel's early developmental stages. This study compares the visualization of underdrawing in images gathered from reflectance imaging spectroscopy in narrow spectral bands with those obtained from infrared reflectography (IRR) in broad spectral bands, a technique widely used in the art conservation field. Passages in which Degas explores various limb positions are better visualized with image products derived from reflectance imaging spectroscopy than broadband IRR images. For example, false-color reflectance images that display narrow NIR spectral bands were useful to separate and visualize the distribution of materials and more clearly convey Degas's processes of compositional refinement. These results provide a deeper understanding of Degas's working method and explore the relationship of Ballet Scene with similar works.