Since their emergence in the second part of the nineteen century, synthetic dyes made from organic molecules have enabled the development of rapid and cost-effective production of textiles worldwide and on a large industrial scale. On the downside, these chemically manufactured dyes produce large amounts of toxic wastewater causing significant damage to living organisms and human health. The proposed paper highlights local knowledge mobilized by Marka-Dafing dyers in developing technics of fermenting textiles in the context of an increasing global need for sustainable and biodegradable dyes and fabrics that reduce environmental impact. The paper explores dyeing technics that Marka-Dafing women of northwestern Burkina Faso in West Africa, have developed over time to mimic indigenous silk: a precious and rare material that is used to weave their wrapper of prestige (tuntun). Grounded into an ethnography of materials, it examines the relationships between plants and the world of bacteria contained in cow dung which is used to enhance the mechanical and optical properties of cotton yarns, not only for making it look like wild silk but also for making the fiber more durable.