AIC's 42nd Annual Meeting

Curators and conservators need to know what they get themselves into when ordering analyses of organic colorants on culturally important heritage objects. They are often confronted with the following dilemma: to destroy or not to destroy? That is, to perform analyses that will ultimately destroy the sample analyzed or to utilize a method that does not alter the original object in any way. This is especially relevant to the study of archaeological artifacts, which often consist of small fragments. Unfortunately, some analysts’ claims that their methods involve ‘non-destructive testing’ (NDT) are in some cases either misleading or erroneous. A true NDT method can be termed ‘non-invasive’, whereas micro-destructive or nano-destructive methods – depending on the scale involved – can be simply referred to as ‘invasive’.


Additionally, museum officials should not be automatically enticed by the razzle-dazzle of impressive-sounding acronyms, such as, FAB, DESI, DART, HRMS, TOF, SERS, and even DAD, which have been used for the analyses of historic colorants. The high-tech world of sophisticated chemical instrumentation has permeated into the field of analytical research of natural colorants. However, the advancement in the sophistication of electromagnetic chemical techniques does not automatically imply that their application to the study of ancient colorant sources is also advanced, or even useful. There are fundamental problems with these spectrometric methods for the analysis of organic dyes and pigments that museum officials should understand, and these will be addressed.


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!


This talk will emphasize the dye analysis results on molluskan-purple pigments from the following historically important archaeological sources: (a) an intricate Late Roman-Period polychromic textile from Egypt; (b) a Roman-Period Royal Purple weave belonging to King Herod found atop the Judean Desert palatial fortress of Masada in Israel; (c) a 2,500-year old marble jar of King Darius from ancient Persia; and (d) other historic examples that shed light on the fashionable colors of kings and biblical priests.