Materials, archaeological dyeing methods

Solution spectrophotometry in the visible and ultraviolet can he used to determine the nature of dyes used to color textiles of archaeological or historical importance. The curves obtained are compared with those from solutions of known materials. The method requires dyeings made with known natural dyes from the region of interest. Collections of such materials have been obtained from Peru, The principle red dyes of Peru can be identified by means of a single solution curve. Blue, from indigo, can easily be distinguished from the purple dibromoindigo obtained from marine molluscs. Yellow dyes are more difficult to identify and require, in most cases, curves in more than one solvent. 

Other workers in the field feel that is important to obtain positive identification with a minimum amount of material. In such cases the most desirable method would be that of spectroscopy. DePuy and Quin-livan have presented a paper on the use of this technique to analyze dyes in archaeological material (17). The combination of thin-layer chromatography followed by mass spectrometry (with or without the formation of a derivative) is, without doubt, the method of the future. Now, however, it is not possible to detect cochineal, one of the most important dyes of early America, by this method. We leave this to the modem chemists who are more familiar with the advances in this special field and wish them luck. Until then we feel that much valuable informa-... 

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