AIC's 46th Annual Meeting

Big Egg (1968) by Ed Clark is a large oval-shaped abstract painting on canvas, created while the artist was working in France. The painting is from the National Museum of African American History and Culture (NMAAHC) collection and underwent technical study and conservation at the Museum Conservation Institute (MCI). Clark is known for his technique of painting with the canvas on the floor, pouring and splashing many thin layers of paint and pushing them around with a large broom. Much of the paint surface has a matte and chalky appearance. Big Egg was originally thought to be acrylic, but preliminary analysis showed the underlying paint layers to be water sensitive and the pigments to be bound in polyvinylacrylate (PVAc) with a possible ethylene co-polymer. Currently, the painting is on view at the Visual Art Gallery at NMAAHC. This study is a continuation of research conducted in 2015-2016 on un-embedded paint samples from Big Egg with ATR-FTIR and Hirox microscopy. In this study, a paint cross-section embedding and polishing technique was developed to further the binder and pigment analysis of each paint layer with FTIR chemical mapping and SEM-EDX. This research is part of broader investigations by the authors with the goal to optimize paint sample preparation for modern and contemporary art. The paint cross-section methodology is as follows: 1) embed the paint sample in Bio-Plastic® 2) mount the embedded sample on double-sided silicon tape onto a glass slide 3) place the paint layers parallel to the glass slide 4) ensure strata of paint is fully on view when the sample is released from the mold 5) use metal tube as mold, ¾” in diameter cut to ¾” height 6) coat the interior of the mold with silicon grease 7) a negligible amount of resin exists between the paint sample and silicone tape resulting in minimal polishing 8) dry polish with MicroMesh 8) use Hirox reflective bright field to confirm paint sample surface topography. The analysis of the paint cross-sections starts from the least invasive technique, ending with the more invasive method—from Hirox microscope examination to FTIR mapping (measured in reflectance mode) to SEM-EDX. Using the methodology listed above, a paint cross- from Big Egg was analyzed and 13 layers of paint were observed. The thickness, inorganic elements, and binder of each stratum was examined by FTIR mapping and SEM-EDX. Water-sensitive PVAc paint in Big Egg was confirmed by ATR-FTIR on non-embedded paint and FTIR mapping of the embedded paint cross-section. This result supports the treatment selection of water-based consolidant, water-based inpainting material, and the choice of Beva film as a lining adhesive. Fully polished paint cross-sections ready for analysis can be prepared within a day. The application has been extended to include egg tempera paint, photographs, and polychrome. This cross-section preparation expands the instrumental analysis capability from one paint sample, maximizing the information gathered. Future work includes more comparative experiments with ion milling systems to improve the paint surface quality and further organic material analysis with FTIR-mapping.