Materials analysis in three paintings of Thomas Gainsborough (1727-1788) by portable X-ray fluorescence

Three paintings of Thomas Gainsborough (1727-1788), one of the most influential English portrait painters of the late 18th century, from the collection of the Museu de Arte de São Paulo (MASP) - "Francis Rawdon" (1783-1784), "Portrait of Mrs. John Bolton" (1770), and "Drinkstone Park" (1747) - were investigated using portable X-ray fluorescence (pXRF), employing a W tube anode and an XR-100CR detector. These artworks represent the only paintings by Thomas Gainsborough located in the southern hemisphere. Through an analysis of the behavior of X-ray line net areas for all identified elements in various regions of the oil paintings, it was observed that XRF accurately identified the original materials: Lead White, Calcium Carbonate, Calcium Sulfate, Bone Black, Ivory Black, Yellow Iron Oxide, Prussian Blue, Vermillion, Red Iron Oxide, Umber, and Sienna Earth. Additionally, certain regions exhibited the presence of 19th century pigments: Zinc White, Cobalt Blue, and Chrome Yellow, indicating areas that had undergone restoration. The findings presented in this study align closely with results obtained from other investigations into paintings by Thomas Gainsborough.