The Significance of the Color Indigo

Used to dye cloth for thousands of years, indigo continues to have significance in modern times. Selected by Sir Isaac Newton to be part of the rainbow spectrum, indigo's violet-blue color remains significant to schoolchildren learning the mnemonic ROY G. BIV.

Sources

Indigo dye comes from the leaves of Indigofera tinctoria, a leguminous branching shrub up to 6-feet tall, and Indigofera suffructiosa. Historically, European clothmakers substituted wode--Isatis tinctoria--for expensive imported indigo.

Chemical Properties

With a chemical structure of C16H10N2O2, indigo includes nitrogen, phosphoric acid, potash and lime. Its dark-blue crystalline powder melts at 390-392° C and dissolves in chloroform, nitrobenzene and concentrated sulfuric acid but not in water, alcohol or ether.

Uses

Uses of indigo include hair coloring, fabric dyeing and treating a variety of diseases. Under Sumptuary Laws in the Elizabethan era, it indicated the wearer's position in society as royalty, nobility or Council member.

Processing Dye

Clothmakers created indigo dye by fermenting the leaves, filtering the product and drying it into cakes of dye.

Symbolic Meanings

Symbolic meanings of indigo include power, importance, wealth, religious ritual and heavenly grace.

References

• "Indigo in the Early Modern World;" Anne Mattson; University of Minnesota
• Natural Cosmetics Supply: Indian Indigo
• Elizabethan Era: The Color Indigo