USE OF LICHENS FOR DYEING:
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Since Pre-Christian times, some lichens produce dyes and have been used for colouring fabrics and paints.
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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.
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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.