La technique des «Primitifs flamands» |
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| Abstract: | AbstractFor the study of Italian paintings and their techniques the examination of the binding media (glue, egg, oil) has considerable importance, but with the usual scientific methods of analysis the results have never been conclusive. Each sample may include more than one layer of paint and many constituents; egg yolk alone contains protein, oils, cholesterol. In the present project, in order to identify these diverse materials and also to eliminate interference from contamination (glue, wax or oil) used in later restoration processes, it was decided to mount original paint samples, including a bit of the ground, as cross-sections in a polyester resin embedding material and then to make the constituents visible under the microscope by using selective staining techniques. Only in this way could the foreign materials be distinguished from the original and the structure of the original layers be understood. Finally, other tests such as the fluorescent antibody technique and thin-layer chromatography could be applied to confirm the results of the staining. In removing over 500 specimens fronl paintings in the Walters Art Gallery precautions were taken to assure sample authenticity, and during the testing at the University of Michigan careful methods of standardization and control were devised, using both fresh and old samples of egg tempera and oil. Two stains, Ponceau S for protein and Sudan Black B for oil, provided the most workable means of identifying the binding media in the majority of the samples studied. A final report will have to await correlation of the material, but certain observations may be made at this stage: (a) 14th century, in primarily tempera paintings a limited use of oil was found associated with a specific green pigment, copper resinate; (b)15th century, the majority of the paintings were entirely of egg tempera, but layers containing oil in the underpainting or in the above-mentioned copper green occurred more frequently; (c)16th century, egg tempera was not replaced by oil, but both were used in a complex layering technique, the media varying layer by layer and area by area; (d)17th century, the mixed technique gradually declined, but egg tempera continued to be associated with the painting of flesh and occasional highlights. |
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