Description

The History and Chemistry of Indigo

Indigo is one of the oldest dyes in human history, used for thousands of years across cultures in Africa, Asia, the Americas, and Europe to produce the distinctive deep blue that has never been satisfactorily replicated by any other natural source. The indigo plant, primarily Indigofera tinctoria, produces a compound called indican, which, when fermented and processed, yields the blue pigment indigo , a substance that is insoluble in water in its natural oxidised state.

Traditionally, reduction was achieved through complex fermentation processes using plant materials, wood ash, lye, bran, and other organic compounds. In modern practice, a chemical reducing agent , sodium hydrosulphite (also known as sodium dithionite) , is more commonly used alongside an alkali such as soda ash. While effective, this chemistry still requires vat preparation and an understanding of the reduction process.

Jacquard Pre-Reduced Indigo simplifies this traditional method by using pre-reduced indigo granules, making vat setup easier and more accessible while still preserving the authentic characteristics of indigo dyeing. The dye is supplied in powder/granular form and must be mixed with water, soda ash, and sodium hydrosulphite to create the dye vat.

Using the Dye

The dyeing process follows the classic indigo sequence: prepare and thoroughly wet the fibre, submerge it in the reduced vat, remove it carefully, and allow it to oxidise fully in the open air until the colour shifts from yellow-green to blue. The fabric can then be submerged again.

Each dip-and-oxidise cycle increases colour depth. A single dip produces a pale sky blue, while multiple dips create progressively darker shades, eventually reaching a rich navy.

Jacquard Pre-Reduced Indigo is suitable for natural fibres including cotton, linen, hemp, wool, silk, and viscose/rayon. It does not bond effectively to most synthetic fibres.