As part of a series of dye analyses of archaeological textiles discovered in the rubbish dump and the fort at Didymoi, one of the praesidia along the caravan road from Koptos to Berenike, in the Eastern desert of Egypt, true mollusc purple has been identified in 8 fragments of clothes. It was used both as unique source of colorant or in combination with red dyes (kermes or madder). The chapter discusses the provenances of these textiles, the social significance of such discoveries in the rubbish dumps of praesidia and the possible reasons for using purple in combination with red dyes. The hypotheses discussed include the following points: - from a social point of view, wearing clothes adorned with true purple dye was probably more accessible to middle and lower classes than it had been thought so far on account of the small number of identifications of mollusc purple in archaeological textiles. This appears to have been allowed by such practices as: using purple mostly for the comparatively small tapestry ornaments of tunics and mantles; using up purple vats until exhaustion; diluting purple (the "conchylian colours" mentioned by Plinius); recycling worn clothing. - the frequent light-pinkish and mauve to dark violet or burgundy colours represented in the clothing of the contemporary mummy portraits from Egypt were meant to represent the true mollusc purple identified on similar archaeological fragments of clothes. This confirms the fascination for this dye, explicit in the abundant literature on purple in Mediterranean antiquity and especially in the papyri and ostraca from Roman Egypt. - from a technical point of view: Letting aside the fascinating field of imitation purples, on which much has been contributed by our former studies of dyes in the textiles from the praesidia, this series of identifications tends to confirm that in Roman Egypt, the most sought after shade of purple was a reddish purple close to the prestigious colour of "Tyrian purple". There obviously existed different purple-dyeing centres and/or dyeing processes. Some dyeing centres may - permanently or seasonally - only have had access to indigo-rich/dibromoindigo-poor mollusc species, or may have used dyeing processes that resulted in indigo-rich/dibromoindigo-poor dyes. Hence the practice of top-dyeing with red mordant dyes?
