The Museum Conservation Institute - Technical Studies
Adapting Spectroscopic Imaging
One area of special interest for the Smithsonian’s Museum Conservation Institute (MCI) is adapting full spectroscopic imaging at multiple length scales from what can be seen with the naked eye down to nanoparticles for the study of cultural and heritage objects as well as research specimens from the National collections. Spectroscopic imaging using ultra violet-visible (UV-VIS), X-ray energy, infrared, Raman shift, etc., each in two dimensions, can be combined to produce datasets that reveal chemical/ molecular information for each pixel in the array and are often referred to as 3-D data cubes or hyperspectral datasets. This comprehensive imaging approach will undoubtedly lead to discovery of object alteration and modification on the macroscopic scale and clues to a specimen’s history and origin on the microscopic and nanoscopic length scales. These datasets can be mined for information long after the initial data are collected, as is typically done in the remote-sensing community’s study of planetary bodies. Our goal is to lead the Smithsonian in building a network of complimentary techniques to allow researchers to zero in on anomalous regions of importance to achieve a greater understanding of specimens. This program will use the instruments and techniques typical of Unlocking the Mysteries of the Universe to serve all of the Smithsonian’s Grand Challenges.
MCI’s spectral imaging team includes Edward Vicenzi – research scientist/geochemist with experience in spectroscopic imaging down to the sub-micrometer level of extraterrestrial and terrestrial materials; Melvin Wachowiak – senior conservator who has expertise in a variety of light microcopies, including 3D scanning, extended focal imaging, replication of objects, and advanced object documentation; Jennifer Giaccai – conservation scientist with expertise in characterization of specimens using a variety of chromatographic and spectroscopic techniques, including imaging using XRF, SWIR, and the mid-IR; and Odile Madden – research associate with expertise in characterization of specimens using traditional Raman and surface enhanced Raman spectroscopy. MCI currently has electron induced X-ray spectroscopic imaging in the SEM and Raman, and over the past year had access to a Bruker ARTAX portable micro-XRF spectrometer. Though our new partnership with SOLEIL Synchrotron we will have capabilities at all image positions (imaging XRD, imaging X-ray absorption, e.g. XANES, and EXAFS, as well as imaging micro XRF).
- Upcoming Microscopy and Microanalysis 2010. Ed Vicenzi, President of the Microbeam Analysis Society, is an organizer of Microscopy and Microanalysis 2010. The meeting will be held in Portland, OR, August 1-5, 2010, and is the premiere meeting for interdisciplinary microanalysis science with ~ 1000 presentations and 2500 attendees distributed over 35 symposia (http://www.microscopy.org/MandM/2010/index.cfm). He is giving an invited talk as well as co-authoring multiple presentations at the meeting.
- Microscopic Imaging Workshop. MCI hosted a two-day workshop on microscopy and digital imaging led by MCI Senior Conservator Mel Wachowiak and three Leica Microsystems specialists. Leica demonstrated two new systems. One a self-contained DVM microscope, a high-resolution portable system that can produce 3-D image mosaics. The other, a DCM3D, shown for only the second time in North America, can produce 3-D information at the sub-nanometer scale, combining confocal and interferometry technology. The 24 participants included staff from seven SI and DC-area museums or research centers, three forensic scientists from the Department of Justice Drug Enforcement Agency Special Testing and Research Lab, and an archaeologist from the State Department.
- Invited talk at McGill University. Vicenzi was one of four speakers from the US invited to attend and present at the May 6, 2010, grand opening of a state-of the-art High Resolution Scanning Electron Microscopy Facility in the Department of Materials Engineering at McGill’s campus in Montréal, Quebec. His presentation was entitled "Hyperspectral Imaging and Microanalysis of Complex Natural Materials."
- New funding for imaging program. Mel Wachowiak, in partnership with the Freer and Sackler Gallery Archives, has been awarded $41,400 from the Collections Care and Preservation Fund to support the preservation and digitization of fragile paper squeeze impressions of inscriptions from ancient Near Eastern archaeological sites from the Ernst Herzfeld Collection. This project will use Reflectance Transformation Imaging (RTI) on the collection. RTI datasets supply an immersive pseudo-3-D experience for researchers and the public. The project will make structural and pictorial data from this large collection available on-line and preserve the materials by reducing the need to handle the fragile paper.
- Grant proposal to NSF. Ed Vicenzi is co-PI on a grant proposal entitled “Materials science of aqueous artificial bronze patina formulations” submitted to the NSF SCIART program with Dick Livingston at the University of Maryland. The proposed research will image and analyze corrosion surfaces and cross-sections of bronze alloys and conservation-applied patinas to mitigate degradation. Focused ion beam (3-D) and scanning electron microscopy (2-D) as well as scanning transmission microscopy (2-D) of the microstructure of the metal-oxide interface lie at the heart of this study.
- Jade Microchemistry. Ed Vicenzi is in the early stages of developing a new method for determining the provenance of jade objects. His approach involves linking of cathodoluminescence (CL) spectral features with trace element chemistry on the micrometer length scale. The initial data are just now being processed and require new software to correlate the two different methodologies. If successful, analysts will have a new mechanism for 2D quantitative trace element imaging of jade via CL, and further trace element ratio imaging may aid in determining the provenance of jades, including “blood jade” from conflict zones around the globe.
- Upcoming Workshop. On May 19 and 21, a next generation scanning X-ray Fluorescence spectrometer workshop will be held at MCI, sponsored by instrument manufacturer EDAX Corporation. This vacuum chamber- or atmospheric-based system is ideal for non destructive elemental imaging of objects at a length scale between macroscopic and microscopic. The instrument will remain at the Smithsonian for a few weeks after the workshop for MCI research scientist Ed Vicenzi and Jeff Speakman, Head of Technical Studies, and other MCI staff to evaluate the spectroscopic imaging datasets collected on SI collection materials and research projects