Unveiling the Invisible in Uffizi Gallery’s Drawing 8P by Leonardo with Non-Invasive Optical Techniques

Alice Dal Fovo,Enrico Pampaloni,Raffaella Fontana,Jana Striova

doi:10.3390/app11177995

Alice Dal Fovo, Enrico Pampaloni + Show 2 more

Open Access

https://doi.org/10.3390/app11177995

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Abstract

Until recently, the study of drawings by old masters has been confined to the art history conservation field. More specifically, scientific investigations of Leonardo’s drawings are still very few, possibly due to the latter’s extreme fragility and artistic value. However, analytical data are crucial to develop a solid knowledge base of the drawing materials and techniques used by artists in the past. In this work, we report on the application of non-invasive optical techniques on a double-sided drawing by Leonardo belonging to the Uffizi Gallery (8P). We used multispectral reflectography in the visible (Vis) and near-infrared (NIR) regions to obtain a spectral mapping of the drawing materials, to be subsequently integrated with technical information provided by art historians and conservators. Morphological analysis by microprofilometry allowed for the identification of the typical wave-like texture impressed in the paper during the sheet’s manufacture, as well as of further paper-impressed traits attributable to the drawing transfer method used by Leonardo. Optical coherence tomography revealed a set of micrometric engraved details in the blank background, which lack any trace of colored material, nor display any apparent relation to the drawn landscape. The disclosure of hidden technical features allowed us to offer new insights into Leonardo’s still under-investigated graphic practices.

Highlights

Scientific analysis of artworks is often performed within the limits of non-invasiveness requirements, which automatically exclude any material sampling or contact measurement
We used multispectral reflectography in the visible (Vis) and near-infrared (NIR) regions to obtain a spectral mapping of the drawing materials, to be subsequently integrated with technical information provided by art historians and conservators
False-color imaging, which was performed on the high-resolution images following the processing described above, revealed traces of the preliminary drawing that outlines the steep cliff on the left of the waterfall and the fortress on the promontory

Summary

Introduction

Scientific analysis of artworks is often performed within the limits of non-invasiveness requirements, which automatically exclude any material sampling or contact measurement. Meeting such requirements, may prove especially challenging when studying paper-based drawings and paintings, whose extremely light-sensitive nature often demands fixed lighting conditions. Minimizing light exposure during measurements without compromising data significance means striking an effective balance between spatial sampling (pixel size) and spectral resolution— an extremely delicate task at best [1,2,3]. Numerous studies indicate that analysis of paper-based artworks is best performed when applying a synergic approach that combines non-invasive analytical tools and complementary optical techniques [5].

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