USE OF LICHENS FOR DYEING:
Since Pre-Christian times, some lichens produce dyes and have been used for colouring fabrics and paints.
Roccella is a dye yielding lichen. The product called Orchil is extracted from its thallus. Orchil is a beautiful blue dye. Orcein is a purified product of orchil.
Litmus solution is made by grinding the lichen Roccella tinctroria, and extracting the colouring matter, after which the paper is soaked in a neutralized solution and is then known as litmus paper.