Hydroxyapatite (HAP) Project

PAPER TITLE: “Preliminary results on biomimetic methods based on soluble ammonium phosphate precursors for the consolidation of archaeological wall paintings”
Magdalena Balonis-Sant, Xiao Ma, Ioanna Kakoulli. Archaeological Chemistry VIII, ACS (2013) 419-447.

BIOMIMETIC METHODS BASED ON SOLUBLE AMMONIUM PHOSPHATE PRECURSORS FOR THE CONSOLIDATION OF WALL PAINTINGS
This research is sponsored by the National Science Foundation Award # 1139227
Division of Materials Research
Program: Solid State and Materials Chemistry

TECHNICAL ABSTRACT
With support from the Solid State and Materials Chemistry (SSMC) program in the Division of Materials Research (DMR), this project will develop hydroxyapatite (HAP) based, inorganic mineral systems to preserve and consolidate powdery wall paintings composed on calcium carbonate (CaCO3) rich plaster layers of archaeological, historic and artistic value. Biomimetic principles are used to induce HAP formation in the decohesive plaster by triggering reactions between the carbonate substrate and the peptidic and ammonium phosphate precursors. Spatially, structurally and compositionally sensitive analytics including scanning electron microscopy, 3D-CT imaging, dynamic vapor sorption methods and mechanical and fluid-transport analyses are applied to quantify HAP treatments. From a scientific perspective, the research describes: (1) chemical interactions and reactions between the phosphate reactant and the CaCO3 plaster and (2) the impact of HAP formation on strengthening the microstructure, and improving the painting?s durability while maintaining the original optical/aesthetic properties. The interdisciplinary nature of this research, at the interface of conservation science, biotechnology and materials science develops tailored conservation treatments that consider fundamental characteristics of the substrate chemistry and structure to prescribe and metricate treatment protocols. The research advances our ability to design, manipulate and evaluate consolidation treatments for porous polychrome surfaces and allows for improved methodologies to preserve global cultural heritage. Significantly, the effort develops conservation strategies for historic objects ranging from paintings and rock-art to stone structures, paleontological fossils and archaeological bone with a basis rooted in the physical sciences and materials engineering.

NON-TECHNICAL ABSTRACT
Wall paintings provide a testimony of artistic, cultural, and intellectual developments and are consequently of profound archaeological, historical and cultural significance. Unfortunately, with the passage of time, wall paintings experience considerable degradation due to their exposure to human activity and environmental forces. While several methods have been proposed to limit or halt such degradation, these methods often compromise the intrinsic quality and attributes of the painting. Through a multi-disciplinary collaboration at the University of California, Los Angeles (UCLA), this research develops hydroxyapatite-based consolidation treatments to enable the protection of multi-layered, polychrome, heterogeneous wall paintings from weathering and deterioration induced by passage-of-time and environmental effects without causing significant change to their physical and chemical properties. By using analytical tools sensitive to the composition and structure of the material, treatment methods are applied and metricated in a context sensitive fashion; i.e., with attention to the characteristics of a specific painting and its execution technique (i.e., fresco or secco). The research and academic training provided to a post-doctoral researcher, a graduate student and several undergraduate students imparts knowledge to a new generation of conservation scientists who can contribute to preserving our collective cultural heritage. Through interactions with national and international collaborators the research offers a platform for academic excellence/exchange and at the same time creates new knowledge of conservation practices applicable across diverse geographical domains. Finally, the research also develops knowledge with applications in bioengineering for tooth/bone reconstruction and for infrastructure rehabilitation in civil engineering. This research is supported by the Solid State and Materials Chemistry (SSMC) program in the Division of Materials Research (DMR).

HAP Presentations

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