The presence of an organic or inorganic residue is identified by screening the submitted artefacts. This screening can employ a variety of methods including microscopy, alternate wavelength spectroscopy, elemental analysis, micro-ATR-FTIR and luminescence. The results are reported with the identification of the presence of a residue and if it is organic or inorganic. This allows for a testing approach for further residue analysis if desired. The types of artefacts that can be screened:
- Lithic (grindstones, points, scrappers etc.)
- Textile Stone (fire cracked stone, hearthstone etc.)
- Trace residue (scrapping, swab etc.)
The submitter can request specific methods to be employed otherwise the choice methds employed is determined by the analyst and depends on the size, shape, and type of artifact. There is a flat screening fee for service and it can be provided as a separate stand-alone service.
In situ Characterization
After the initial screening of the artifacts for the presence of a residue and the identification of whether the residue is organic or inorganic, characterization of the residue begins. This process will employ various techniques of microscopy, spectroscopy and micro-chemical tests. All of these tests are employed in a non-destructive manner where the residue is not removed from the surface of the artefact. Our report will then address the source of the residue whether it is anthropogenic or could be from the environment and whether these sources are contamination or not. Depending on the presence of specific microstructures (hair, fibres, pollen, starch) will determine whether the residue can be assigned to a plant, animal or mixture of both sources. This can then lead to the identification of specific tissue and is some cases taxonomic identification.
Residue removal is one step in the process for a complete residue analysis however it can also be a separate service as requested (for example, If residue needs to be removed for radiocarbon dating or other services not provided through LUMARS). The residue removal can be performed with a variety of solvents, solutions and buffers all specific to the downstream methods being employed. Removal can be performed as a dry removal, spot removal, target surface areas or whole surface removal depending on the degree of sampling and preserving the residue.
Residue Characterization and identification
The final step in a complete residue analysis is final characterization, identification where possible and interpretation. There are a number of sample types that can be analyzed in the same manner as residue off the surface of an artifact.
- Soil from feature pits
- Pigment caches
- Latrine soil
- Site soil for functional or work area determination
- Manufacturing raw material (pieces of resin, beeswax etc.)
There are many methods employed in this final stage some are applied routinely to every analysis and some that varies the costs for analysis. The routine analyses include:
- Alternate wavelength spectroscopy
- Biochemical and micro-chemical tests
- Physio-chemical test
- Absorbance spectroscopy
- Histological tests
- Enzymatic tests
These various methods can be requested as a separate service or LUMARS will consult with the contributor for the scope of characterisation and identification.
- Starch analysis
- Phytolith analysis
- Fibre analysis
- Pollen analysis
- Parasite analysis
- Hair analysis
- Feather analysis
For example some contributors request GC-MS of cooking residue on ceramic material or GC-MS on hafting residue on lithics as a single service, this is consistent with the Molecular and Archaeological Chemistry services and are outlined below.
Archaeochemistry and Molecular Services
LUMARS provides archaeochemistry and molecular services for the characterization and identification of a large range of substances and molecules This service is specific to the molecule of interest but can be performed on unknown substances for characterization.
- Elemental analysis (ICP-AES, ICP-MS, XRD, XRF)
- Immunological tests
- Genetic analysis
- Isotope analysis
- Protein analysis