Archil

Archil is a red or violet dye obtained from various species of lichens belonging to the genera Roccella, Dendrographa, and Orchilla. The dye has been used for centuries, particularly in Europe and the Mediterranean region, for dyeing wool and silk.

Production:

The process of extracting archil involves treating the lichens with ammonia, often in the presence of urine or potash. This fermentation process produces a colored compound that can then be extracted and used as a dye. The resulting dye is sensitive to pH, turning redder in acidic conditions and bluer in alkaline conditions.

Historical Significance:

Archil played a significant role in the textile industry before the advent of synthetic dyes. Its vibrant colors made it a popular choice for creating rich and luxurious fabrics. The islands where archil-producing lichens grew were often highly valued for their economic importance.

Chemistry:

The active coloring agents in archil are orcein and related compounds. These are complex organic molecules derived from orsellinic acid.

Modern Use:

While largely replaced by synthetic dyes, archil is still used in niche applications, such as food coloring (E120, also known as carmine, often confused with archil but typically derived from cochineal insects) and for scientific purposes, particularly in pH indicators and microscopy. Its natural origin and unique color properties contribute to its continued, albeit limited, use.

Synonyms and Related Terms:

• Orchil
• Orseille
• Persio
• Cudbear (a similar dye derived from different lichens)