Abstract:

Fourth year students in the baccalaureate program in chemical engineering at my college are required to perform faculty-supervised original experimental research in any area of science and engineering. As the college comprises faculties in engineering, design, and art, my goal was to introduce my research students to one of the more humanistic areas of science – the scientific study of ancient cultural heritage objects and related technologies. This is accomplished by applying high-tech science using modern chemical instrumentation to the study and understanding of one of the technologies practiced in antiquity. This artistic and scientific technological craft is the production of color on an object, whether by the dyeing of textiles or by the painting of walls and vessels.

The study of the natural colorants used in antiquity opens a historical window to one of the most fascinating chapters in the field of ancient technologies. Such an investigation involves an interdisciplinary approach that combines history, archaeology, art, religion, botany, entomology, malacology, and forensic-style analytical research. The results of the analyses of ancient dyes and pigments can lead to a better understanding of international commerce in antiquity, especially in the flow of dyestuffs, dyed goods, and of dyeing technologies from one geographical region to another. The "fashionable colors" of ancient peoples can be better visualized by studying the chemical constitution of these colorants through the centuries from the various archaeological textiles of different eras that have survived the ravages of time.

The optimum analytical method to be used in the analysis of organic dyes and pigments is the high performance liquid chromatographic (HPLC) technique, which must be preceded by a correct dye micro-extraction procedure. Though this method essentially destroys the sample, it is nano-destructive and more than any other method extracts the maximum information regarding the origin of the dyestuff used. This method has been successfully used on such miniscule samples as single dissected fibers from a yarn, whereby the dye quantity was on the order of a nanogram – a billionth of a gram!

Though the students apply the techniques to very specific items, they learn a number of universal skills that can be applied to many different fields in their future professional careers. These proficiencies include micro-sampling of the objects for the analyses and handling such miniscule samples; understanding the principles of chromatography in general, and liquid chromatography in particular; being able to critically interpret the scientific results by knowing what qualitative and quantitative data can be accepted or rejected; and applying their scientific results by extrapolating back in time to identify the natural source of the color on an object and to determine the technology that produced that tint.

The presentation will discuss some of the more important studies performed with my students in researching ancient organic colorants. Case histories of historically important archaeological dyes and pigments from plants, insects, and sea snail sources will be described. These include 2,000 year-old Roman Period textiles excavated at King Herod's palatial fortress at the mountain-top cliff of Masada in the Judean Desert of Israel, 3,000 year-old Phoenician purple pigments, and a 4,000 year-old Egyptian textile.

Keywords:

Colors, dyes, pigments, archaeology, chromatography, HPLC, chemistry, chemical engineering.