-
121The red-brown ground contains iron oxides, calcium, and alumino-silicates (Fe, Ca, Al, Si, O, Mg, Mn). Multiple paint layers were found to contain lead-antimonate yellow (Pb, Sb), lead white (Pb), and earth colors (Fe, Si, O, Mn). The presence of phosphorous in the black paint layer indicates the presence of bone black (P). Images obtained using x-radiography confirmed that these colored paint layers beneath the black most likely correspond to a hidden figure that is present beneath the shield. Top Left: Visible light/200x magnification;<br/><br/><i>Top Right: BSE image/997x magnification; Bottom left and right: EDS elemental maps (Major Elements: Si, O, Pb, Al, Ca, Fe; Trace: K, Mg, Sb)</i>
-
122While microscopic examination is commonly performed on <a href="http://www.artcons.udel.edu/about/kress/examination-techniques-and-scientific-terms/cross-sectional-microscopy" target="_blank">paint cross-sections</a> and dispersed pigment samples, the use of a scanning electron microscope that is capable of energy dispersive X-ray analysis (referred to as SEM-EDX) can be of equal importance. A paint cross-section is placed inside a vacuum chamber and an electron beam is focused on the exposed surface of the sample. Two types of images can be generated using SEM-EDX. An SEM back-scattered electron image (BSE image) provides visual information relating to pigment morphology as well as the range of atomic weights present (e.g. light areas correspond to elements with higher atomic weights such as lead while darker areas indicate lower atomic weight elements). The second type of image, referred to as an EDX map, is generated using very similar technology described in the X-Ray Fluorescence section (link to XRF site) X-rays excite electrons present on the surface of the paint sample, generating elemental information that can help scientists and conservators identify pigments (typically inorganic such as those obtained from crushed up stones and minerals) present in discrete paint/ground layers.<br/><br/>Samples collected from the "Triumph of David" were prepared by project leader Kristin deGhetaldi and examined with scientist Catherine Matsen at the Winterthur Museum Scientific Research and Analytical Laboratory. A Zeiss EVO MA15 scanning electron microscope was used with a LaB6 source at an accelerating voltage of 20kV for the electron beam, stage height of approximately 11mm, and sample tilt of 0 degrees. The EDS data was collected with the Bruker Nano X-flash(R) detector 6|30 and analyzed with Quantax 200/Esprit 1.9 software.
-
123This sample was collected from the shot-silk robe of the woman holding the tambourine after removal of the degraded surface coating. The red-brown ground contains iron oxides, calcium, and alumino-silicates (Fe, Ca, Al, Si, O, Mg, Mn) while the paint layers appear to contain iron oxides (particularly green earth; Fe, Si, Mn, O) and lead white (Pb).<br/<br/><i>Top Left: Visible light/200x magnification; Top Right: BSE image/259x magnification; Bottom left and right: EDS elemental maps (Major Elements: Si, O, Ca, Al, Pb, Fe, K; Trace: Mg, Mn, Na, Ti)<i>
-
124This sample was collected from the blue robe worn by the kneeling woman in the lower right corner before removal of the degraded surface coating. The red-brown ground contains iron oxides, calcium, and alumino-silicates (Fe, Ca, Al, Si, O, Mg, Mn) while the dark blue paint layer appears to contain an extremely pure grade of lapis lazuli (Al, Na, Si, O) followed by a thin layer of lapis mixed with lead white (Pb). In this particular sample the upper layer of the double ground is extremely thin and can only be detected in the EDS map for iron. A large red, iron oxide particle can also be seen in the lower left.<br/><br/><i>Top Left: Visible light/200x magnification; Top Right: BSE image/264x magnification; Bottom left and right: EDS elemental maps (Major Elements: Si, O, Ca, Al, Pb, Fe, K, Mg; Trace: Na)</i>
-
125This sample was collected from a heavily overpainted back of the kneeling woman in the bottom right corner. The red-brown ground contains iron oxides, calcium, and alumino-silicates (Fe, Ca, Al, Si, O, Mg, Mn) while the uppermost layer of overpaint contains Zinc White (Zn), a pigment that was not available to artists until the 19th century. Spot analysis of red and yellow pigment particles mixed into the original lead-containing paint layers confirmed the presence of vermillion (Hg) and lead-antimonate yellow, most likely Naples Yellow (Pb, Sb). Top Left: Visible light/200x magnification;<br/><br/><i>Top Right: BSE image/302x magnification; Bottom left and right: EDS elemental maps (Major Elements: Pb, O, Si, Ca, Al, Zn, Fe; Trace: K, Mg, Mn, Hg, Sb)</i>
-
126Continued cleaning and consolidation on upper section of painting. Began consolidation and overpaint/varnish removal throughout top half of painting.
-
127
-
128
-
129
-
130
-
131
-
132
-
133
-
134Continued cleaning and consolidation on upper half of painting. Significant portions of the sky and background architecture were found to be heavily overpainted (Pictured here: Ellen Nigro).
-
135Removal of darkened, discolored overpaint and blanched varnish revealed a beautifully executed head depicting an older soldier.
-
136Significant areas of blanched varnish were found covering sections of the flowers, particularly the green leaves that were painted using green earth or terre verte
-
137
-
138Viewing the painting using oblique, raking light helps to illuminate areas that remain covered by the thick, glossy varnish and overpaint. In this image only Abner's head, neck, and clothing has been cleaned.
-
139
-
140In normal visible light other details were noted during the cleaning process. Curious striations and patterns became visible throughout Abner's head and neck; upon closer inspection the team realized that the artist had made a significant change in this area of the composition. From the tiny losses in Abner's face it is possible to detect a cool, grey color coming from underlying paint layers. Read more in the Infrared Reflectography and X-Radiography sections.)
