Fig. 4
From: Salvator Mundi: an investigation of the painting’s materials and techniques
Cross-section sample 4 from background, visible light (top) and ultraviolet fluorescence illumination (bottom), showing: (1) ground, (2) imprimitura, (3) initial black paint layer, (4) warm brown underpaint, (5) three black paint layers. Over these paint layers is a fluorescent, unpigmented layer and an uppermost green layer representing non-original overpaint; this aspect of the painting has been discussed in a separate publication detailing the restoration treatment [2]