XRF Applications on Native American Collections

Transcription

1 XRF Applications on Native American Collections Cheryl Podsiki The Field Museum, Chicago Symposium School for Advanced Research Indian Arts Research Center, Santa Fe, NM May 28, 2009

2 Applications Manufactured for use in Environment: Soil samples Modern Metal Alloys: Scrap metal industry Analytical Standards Adapted for use by Health Department: Lead paint, asbestos, plastics, electronics, toys, pesticides Museum Collections and Research: Metal alloys, glass, ceramics, obsidian, minerals, pigments, paints, mordents, textiles, paper, leather, hide, skin, fur, felt, feathers, shell, bone, ivory, plastic, minerals, geological specimens, taxidermy specimens, pesticides

3 Conservation Use in Collections Bruker-AXS Tracer III-V analyzer, Rhodium source Analysis of unknown residue Pesticide Check Pigment identification Glass: Lead

4 Archaeological Field Work Innov-X Alpha Series, Tungston source Lab set-up for obsidian Portable XRF for floor chemistry

5 Archaeological Metals Wari Tupu AD LA-ICP-MS : Cu and As 1.98% Hopewell Antler Headdress: Native Copper; Reconstructed for WCE, 1893, using iron based metal rods, plaster, pigments, adhesive; Subsequent conservation repairs used wood dowels, more pigments, different adhesives. Lead top to condiment bottle; early 20 th century. XRF

6 Confirmation of Lead Glass Eyes 33 kv; 2.20 µa; Titanium- Aluminum filter; no vacuum; 60 seconds. Buddha face gesso / wood (red) over glass eye (blue).

7 Archaeological glass, Glass Beads, Ceramics, Obsidian, Chert Cadmium, Zinc, Arsenic, Lead Cadmium, Zinc Cadmium, Zinc Lead, Arsenic Lead, Arsenic Glass beads from Kenya analyzed with LA-ICP-MS; XRF

8 Elements Detected by XRF * * * As * * Hg Pb * * *

9 Heavy Metal Pesticide Residues Detected Arsenic compounds [inorganic] Lead or lead compounds [inorganic] Mercury compounds [likely inorganic, possibly organic] Zinc compounds [inorganic] Ethylene bromide (bromine residue remains) Ethylene dibromide [fumigant] (bromine residue remains) methyl bromide (bromine residue remains) Methylene bromide [halogenated hydrocarbon] (bromine residue remains)

10 Spot Tests Merckoquant Arsenic Test Plumblesmo Test for Lead Mercury Indicator Powder Slide Test

11 XRF Analyses with Zuni Tribal Representatives

12 Testing Process: options, flexibility Short Pre-test Visit by Tribal Representatives to Museum Cultural handling, restrictions, issues, concerns Tribal reason (s) for test: use, retire, storage Basic methodology for using XRF Documentation requested by Tribe and by Museum Longer Visit for purpose of conducting XRF analysis together *Discuss issues connected to XRF analysis Better idea of sample sites and documentation needed Museum staff completes testing and final documentation Visit by museum staff to tribal community to present and discuss results/demonstrate XRF analyzer.

13 Mapping Sample Sites

14 Mapping and Results Documentation Sample site 1 broken blue beads Arsenic (As)* Bromine (Br) Lead (Pb) x nd x nd 2 red beads x nd x nd 3 yellow beads nd nd x nd 4 dark blue beads nd nd x nd 5 sky blue beads x nd x nd 6 pink beads x nd x nd 7 green beads nd nd x nd Mercury (Hg) 10 8 buckskin toe, top nd nd x nd 9 buckskin toe, bottom nd nd x nd red fabric lining 11 buckskin heel, back x nd x possible nd nd x nd 12 Tyvek insert support nd nd nd nd Test date: 2/10/2007 Instrument operator/handlers: Cheryl Podsiki Instrument: Bruker-AXS Tracer III-V analyzer Voltage (kv): 40 Current (μa): 8 Filter: Copper-Titanium- Aluminum Vacuum: No Acquisition time: 60 seconds Test Notes: The broken blue beads contain lead and arsenic, but the buckskin toe # 8 showed only a comparative trace of lead (likely from cross-contamination of bead residue) and no arsenic. Readings taken from the toe, heel, and bottom of the buckskin showed the same results. The presence of arsenic is likely from glass composition and not from pesticide. The Tyvek support was checked for cross-contamination purposes.

15 Continued Care

16 Pesticide or Inherent? The blue beads are deteriorating due to glass disease. Glass residue is present in the housing container and on the bottom surface of the moccasin.

17 Spectra overlay of Buckskin and Beads The broken blue beads (blue spectrum) contain lead and arsenic. The top of the buckskin toe (red spectrum) exhibits very little lead and no arsenic. It is likely that the presence of lead and arsenic is due to glass manufacture and not pesticide.

18 Pigments on Objects Cinnabar/Vermilion Rare red Chinese paper rubbings, Laufer collection, Vermilion Red Lead Realgar (mercury) (arsenic)

19 Lead Blue spectrum is the red pigment; red spectrum is the bare wood. Red pigments tested Mercury Blue spectrum is the red pigment; red spectrum is the bare wood.

20 Feathers Seed bead and feather necklace from South America Brown Feather. 40Kv; 8µA; Copper-Titanium-Aluminum filter; no vacuum; 180 seconds.

21 Wood Box Box exterior (red) over interior (blue). 40Kv; 8µA; Copper-Titanium-Aluminum filter; no vacuum; 60 seconds.

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23 Red Pigmented Buckskin Pouch Exterior (red) over Interior (blue). 40Kv; 8µA; Copper-Titanium-Aluminum filter; no vacuum.

24 Buckskin Ceremonial Item Exterior front center (red) over interior front center (blue). 40Kv; 8µA; Copper-Titanium-Aluminum filter; no vacuum; 60 seconds. Spot test for arsenic was positive.

25 Natural Pigments: Two Yellows Two yellow pigments: Sample 10, a calcium based pigment, (blue spectrum), exhibits a significant arsenic peak compared to Sample 11, a silicon based pigment (red spectrum), which exhibits a much lower arsenic peak.

26 Natural Pink Pigment The silicon and iron based pink pigment exhibits a fairly significant arsenic peak. Results of laser-ablation (LA-ICP-MS) analysis show 698 ppm arsenic in this sample.

27 Issues encountered Museum Field Museum has massive collections with wide range of materials but resources are lacking for further research/experimentation: funding, staff, department priorities same problem as in other non-university museums and smaller institutions Isolation of issues unless network with other users Practice and experience is a must for interpretation; lack of resources for support. XRF Spectral interference Interpretation: subjective; two people needed Need standard reference materials to provide semi-quantitative results Results: even semi-quantitative or quantitative results cannot answer the ultimate question: What does it mean? Must get medical community involved.

28 Team approach Cultural representatives cultural, spiritual, legal Conservator/collections manager past and present museum procedures and object history; material characterization; conducts test; interprets results Analytical chemist or physicist primary or secondary interpretation of results; conducts test Medical / health professional such as a toxicologist, industrial/occupational hygienist safe handling guidelines; health effects Manufacturer scientist of specific instrument shares pertinent information about instrument and known applications; R & D to continue development of needed technology for museum application Wider circle of XRF users/institutions network; share information; research; beginners, previous users and experts

29 The issues are complex and resources too little an information network among XRF users and institutions is vital to finding solutions. Participants, 2008 XRF Seminar at The Field Museum