The subtle glow of lichen dyeing

Lichens are known for an often large amount of secondary metabolites (substances not produced for vital processes). Many of these have been used as dyestuffs. Nevertheless, they never have been really popular. They may hold well in washing, but their lightfastness in sunlight is almost desastrous.
On the other hand, lichens provided a broad range of colours, not readily available from other (plant) sources. They remained in use as a addition to other dyes, especially in coastal and Northern areas where lichens were abundant. Annette Kok, in a much-referred-to article in The Lichenologist puts it: "It is not only the shade but the quality of the color which seems to be unique; these dyes actually impart a softness and lustre both to silk and wool, whereas many dyes from other sources and their associated processes of mordanting are harmful to these fibres and have to be used with the greatest care so as not to produce harsh cloth and lustreless colors."

One of the earliest articles on lichen dyeing is the brilliant thesis of German biologist Georg Franz Hoffmann, printed in the Erlangen of 1786.
Dedicated to the general uses of lichens, it describes many old uses of dyeing. 27 species are mentioned. While the colours produced are rather vaguely put down ('armeniaco-cinnamoeus', 'cinereo-cervino' and 'spadiceo-flavescentem' for example), Hoffmann later provided plates to the work in a new version ( with a French summary).