Laboratory testing constitutes processes that are used to study, date and/or authenticate materials by chemical analysis. Since the advent of "New Archaeology" in the 1960s, the use of scientific techniques has grown in importance predominately pertaining to architectural and/or fine art pieces. This trend is directly reflected in the increasing application of the scientific method analysis.
The analytical technique(s) selected will ultimately depend on what type of artifact(s) one wishes to study. This article outlines processes for analyzing different artifact classes and describes popular techniques used to analyze each class of artifact. Keep in mind that archaeologists frequently alter or add techniques in the process of analysis as observations can alter original research questions.
X-ray fluorescence (XRF) analysis and thermoluminescence (TL) technologies.
The thermoluminescence technique can evaluate age by measuring the accumulated radiation dose in the object. This technology requires a very small amount of sample to test (approximately 2 mg, which must be drilled).
To get a better approximation of the age of an object by thermoluminescence, it is necessary to know the composition of the composite, particularly the amount of beta emitters (potassium, uranium, and thorium) present in the clay. This is done with XRF.
Handheld XRF (X-Ray Fluorescence) is a nondestructive tool that emits X-rays to determine the elemental composition of an object. This added information helps determine a more accurate age for the pottery and other artifacts. XRF is nondestructive, fast, and can analyze a wide range of materials for evaluating precious artifacts.
Common Materials Tested with XRF for Artifact Analysis
XRF evaluates a wide variety of materials to identify genuine art and artifacts. Common items tested include:
Iron, steel, silver, gold, bronze, copper, and platinum
Clays and pigments for pottery and other artifacts
Gemstones, including jade and sapphire in ancient jewelry
Clay analysis: XRF analyzers can run a full analysis, providing important information on clay items that can help determine if they are original to form and/or restored.
Pigment analysis (clays, paints, inks) Modern pigments contain different elements such as titanium Oxide discovered in the 1900’s.
Metal analysis: Identifying the elemental composition of a metal artifact enables to determine its approximate age. Once composition is know, the analysis must then align with compatible time period known comparables.
Bone, Antler, Teeth, Ivory:
For the analysis of bone samples, collagen which holds the inorganic part of the bone together, is extracted. Samples must be clean and dry when analyzed. Damp samples promotes mold which can cause deterioration of the collagen. The cortical Bone (hard part of the bone) is preferable.
Bone samples can fail to produce collagen if degraded or the bone has been charred. If the bone is friable, the collagen has likely been degraded and requires Ultrafiltration (concentrate longer intact protein molecules and/or remove shorter chain proteins originating from contaminants.)
For teeth, the dentine (the root) is most reliable for dating as the enamel exchanges carbon with the environment, and generally have better collagen preservation. Dentine also has a higher initial collagen content.
Collagen yield, atomic C:N, δ13C and δ15N (by EA-IRMS) are reported with all bone collagen dates as a QA measure.
Charcoal and Wood:
The radiocarbon age of wood corresponds to the growth year of the ring. Depending on the research question, the most appropriate date will be from the outer tree rings. Where year to year differences in F14C (radiocarbon measurements) are desired, individual tree rings will undergo an α-cellulose extraction.
Charcoal samples are floated, or sieved from any accompanying sediment in chemical pre-treatment methods, dried at temperatures less than 70°C, freed of any rootlets or other signs of physical contamination and/or post-depositional carbonates as well as humic acids.
Shell and other carbonates:
Physical pre-treatment of shells for analysis involves removal of outer layer of shell, as well as recrystallized areas to isolate aragonite only.
Samples may undergo a chemical pre-treatment involving the dissolution of the outermost shell in dilute HCl (Hydrochloric Acid).
Small or powdered samples can not undergo this stage of pre-treatment.
Sample powdering is completed under an inert gas (i.e. N2, Ar, etc.).
powdered samples must be stored in glass vials. If the samples are of marine origin, collection site comparables are incorporated in the calibration of results.
If the use of enriched 14C (i.e. tracer 14C. Carbon-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method to date archaeological, geological and hydrogeological samples) is suspected at a study site and/or laboratory, a series of swipe tests must first be carried out to rule out gross levels of 14C contamination for radiocarbon analysis.
Swipes are conducted by liquid scintillation counter(A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses.)
To conduct a swipe, a pre-combusted quartz fiber filter wetted with methanol is rubbed over a surface suspected of being contaminated with 14C tracer (lab counters, fume hoods, door handles, common science store counters, etc.).
Radiocarbon Technical specifications click here