The Assessment of Natural Pigmentation in Archaeological Wool

Naturally coloured wool contains pigment grains that mainly occur as ellipsoidal organelles (eumelanin) or spher¬ical grains (pheomelanin). Eumelanin is the most commonly occurring pigment, but naturally coloured wool fi¬bres contain both eumelanin and pheomelanin. In black and brown wool, the majority of the grains are eumel¬anin, whereas red and yellow wool contain mainly pheomelanin. Transmitted light microscopy of whole mounts of the fibres is commonly used for the detection of natural pigment grains. However, it can be difficult to detect the pigment grains exclusively by transmitted light microscopy of whole mounts of fibres. Archaeological fibres can be degraded and soiled, thereby complicating the detection of the pigments. Sometimes, it can be difficult to determine whether the fibres are coloured because of the natural pigmentation or if the colour is caused by a natural dyestuff. This can especially be the case if the pigments are degraded. When analysing the textiles from Lønne Hede (a Danish Iron Age inhumation grave), it was difficult to gain exact information about the natural pigmentation in some of the samples. To investigate this further, four samples of red-brown yarns from patterned fragments were selected for analyses. Earlier dyestuff analyses of the red-brown yarns gave no results, and it was therefore necessary to test the yarns for natural pigmentation. Three different methods were used for the analy¬ses. Transmitted light microscopy of whole mounts of the fibres, transmitted light microscopy of cross-sections dyed with Toluidine Blue O, and transmission electron microscopy of cross-sections. The results showed that it was difficult to detect any pigments by transmitted light microscopy of whole mounts of the fibres. Transmitted light microscopy of dyed cross-sections improved the results making it possible to suggest that some fibres contained pigments and, furthermore, describe the distribution within the fibres. However, in transmission electron micros¬copy, it was possible to gain exact knowledge about the pigment grains in the fibres and especially information on their condition. This showed that one of the yarns contained a fairly large amount of pigment grains (enough to account for the red-brown colour). However, the pigment grains were severely damaged, which explained why it was difficult to see the pigmentation in the whole mounts of the fibres. Instead of pigment grains, the fibre contained empty holes or partly empty holes. The three other yarns contained very little or no pigment grains.