Ethnolichenology

Ethnolichenology is the study of the relationship between lichens and people. Lichens have and are being used for many different purposes by human cultures across the world. The most common human use of lichens is for dye, but they have also been used for medicine, food and other purposes.

Lichens are a common source of natural dyes. The lichen dye is usually extracted by either boiling water or ammonia fermentation. Although usually called ammonia fermentation, this method is not actually a fermentation and involves letting the lichen steep in ammonia (traditionally urine) for at least two to three weeks.

In North America the most significant lichen dye is Letharia vulpina. Indigenous people through most of this lichen's range in North America traditionally make a yellow dye from this lichen by boiling it in water.

Many of the traditional dyes of the Scottish Highlands were made from lichens including red dyes from the cudbear lichen, Lecanora tartarea, the common orange lichen, Xanthoria parietina, and several species of leafy Parmelia lichens. Brown or yellow lichen dyes (called crottle or crotal), made from Parmelia saxatilis scraped off rocks, and red lichen dyes (called corkir) were used extensively to produce tartans.

Purple dyes from lichens were historically very important throughout Europe from the 15th to 17th centuries. They were generally extracted from Roccella spp. lichens imported from the Canary Islands, Cape Verde Islands, Madagascar, or India. These lichens, and the dye extracted from them, are called orchil (variants archil, orchilla). The same dye was also produced from Ochrolechia spp. lichens in Britain and was called cudbear. Both Roccella spp. and Ochrolechia spp. contain the lichen substance orcin, which converts into the purple dye orcein in the ammonia fermentation process.

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