1. Introduction
The invention of synthetic colourant at the end of the 19th century triggered a marked decrease in the wide and exclusive use of natural colourants for colouration of materials. Synthetic dyes were judged “better” in any aspect of use, such as brilliance and range of colour, durability and costs. As a result only limited research activities were executed during the 20th century, a considerable part of them located in the field of conservation, restoration and also analysing traditional dyeing procedures as part
of cultural history [1e3]. During the last few decades growing interest in the use of