Clostridium used in mediaeval dyeing

Abstract

Before chemical methods of reduction were introduced in the past century, dyeing using the pigment indigo required a fermenting woad vat to reduce the insoluble indigo to a soluble form1,2. We have reproduced mediaeval techniques of woad preparation3 and fermentation, and find that a thermophilic Clostridium bacterium was responsible for the reduction of indigo.