METHODOLOGY

Sample Preparation

       Before I could perform the electron microprobe analysis, I had to prepare samples that I extracted from each bottle. I first cut a small piece off of each sample using a diamond saw. I then placed the small pieces in plastic casting cups and poured casting resin into each cup. When the resin dried, I grinded each cup using sandpaper grit laps until the surface of the sample was exposed and then proceeded to polish each sample. The polished samples were then placed in a carbon coating machine, which made the surface of each sample surface conductive.

Microprobe Analysis and X-Ray Fluorescence

       I performed x-ray fluorescence analysis and electron microprobe analysis in order to develop data from the samples collected and gain insight into the chemical composition of each bottle.
       X-ray fluorescence analysis (XRF) was performed on bottle samples while I was in northern Chile. All of the measurements were taken using a vacuum in order to enhance the portable XRF instrument’s ability to detect lighter elements. It is a non-destructive analytical technique that determines the chemical composition of each bottle. Although it has a higher detection rate than microprobe analysis, results aren’t typically as accurate. The XRF graphs indicate the prominence of each element (higher the peak, more prominent the element).  
       The polished samples were analyzed by the electron microprobe, which combines scanning electron microscopy (SEM) and compositional analysis using x-ray spectrometry to discover the recipe or “formula” of each bottle. Multiple points on the sample surface were selected for measurement in order to take into account the possible surface variability. The conditions for the analysis were: 15 KeV (kiloelectron) voltage, 15 nA current, and 3 µm beam diameter.  
       The chemical formulas/compositions gathered from XRF and the electron microprobe analysis can shed light into the bottles’ manufacturer and date of production. I plan on matching the chemical formulae of the bottles to formulae utilized by bottle manufacturers and determine who produced the bottles and when they were manufactured. I am currently in the process of interpreting the electron microprobe data and XRF data with Dr. David Scott, chair of the UCLA/Getty Program in Archaeological and Ethnographical Preservation.

Comparative Stylistic Analysis

        A comparative stylistic analysis of the bottles can provide insight into their contents, origin, function, and date, thereby supplementing the scientific analysis. By comparing the vessels to similar looking bottles in sources such as Antique Glass Bottles, I can gain some important background information and assess whether any argument can be made for or against the temporal continuity of a cultural tradition throughout the Tarapaca Valley (Bossche 2001). My interpretation section of this website is primarily based on my comparative analysis.

Polished samples ready for microprobe analysis