“Natural dyes possess additional beauty because they come from living things... I sometimes feel that some of that life is still there.” - Jim Liles| Natural dyer
Throughout history, people have dyed their textiles using common, locally available materials. Archaeologists and researchers have found evidence of textile dyeing dating as far back as to the Neolithic period.
Natural dyes come from a variety of sources
- Plants: Leaves, stems, barks, flowers, roots and fruit
- Insects: Cochineal, Lac , kermes (reds only)
- Mollusks: give purple
- Lichens: Work best on protein fibers
- Mushrooms: Work best on protein fibers
There are many conditions that affect the color, produced by natural dyes, e.g. Season, growing conditions, soil conditions, water, harvesting, storage etc. Most natural dyes are water soluble. There are two exceptions Indigo and Tyrian purple which are vat dyes. They are insoluble in water and require alkaline reduction, this changes the dye into a soluble compound that is able to penetrate the fiber and adhere to it. Through oxidation which is opposite of reduction the original dye forms inside the fiber after dyeing and is permanently attached.
For the most part, edible plants and fruits do not contain dyes suitable for textiles, even though they are rich in color and give a dye, the dye does not fare well when exposed to light and fades on washing. However, dyes extracted from edible plants and berries can be used to make inks for painting or writing.
It is often seen when tinctoria is a plant’s species name, it indicates that the plant is traditionally used for dyeing. E.g. Isatis tinctoria (Woad). The species name officinale indicates a medicinal plant e.g. Rheum officinale (Chinese rhubarb). Many medicinal plants are good for dyeing.
Plants or insects itself are not the dye. They contain multiple dye compounds and each compound in the plant has its own chemical name: Luteolin, alizarin or Juglone. Familiarity with different dye compounds in the dye source help understand the similarity and differences and the handling and processing, along with harvest, extraction and storage.
All dyes are classified into two primary categories:
- Chemical group, which defines the main chemical compound in the dye.
- Dye class, which indicates how the dye is applied to the textile.
There are 6 major chemical groups which a dye can be categorized into
- Anthraquinoids: this compound is found mostly in the organic material that give a red. These include both insect dyes and root dyes. Eg. Cochineal and madder.
- Naphthoquinoids: Henna and Walnut
- Flavonoids: most of the plants that give yellow dyes are rich in this compound.
- Indigoids: Indigo and mollusk purple these are vat dyes and require a different dyeing process.
- Gallotannins: These are mostly colorless or yellow dyes
- Condensed tannins: These are usually brown or reddish brown
Many dye plants contain dyes from than one of these chemical groups. For instance, pomegranate rind contains both gallotannin (making it rich in tannins) and a flavonoid dye. Madder root contains both anthraquinoid dyes and tannins.
Anthraquinoids: is a combination of two words referring to chemical structures. Anthracen a carbon structure consisting of three connected rings. Quinon is the oxygen bound to carbon on the middle ring. Most of the red natural dyes have this molecular structure in the dye molecule. Anthradquinoids are the most colorfast dyes. They can be used as mordants dyes and can sometimes be applied directly and are suitable for one bath acid dyeing.
Naphthoquinoids: Naphthen a chemical structure consisting of two connected carbon rings and Quinon, which is the oxygen attached to one of the rings. Naphthoquinoids dyes can be used as mordant dyes and also as direct dyes.
Flavonoids: This group name is from a Latin word Flavus which means yellow. Flavonoids are a source of the bright colors in a plant and most importantly they are the source of yellow dyes. These include Luteolin, quercetin, apigenin and many others. Flavonoids always require mordants.
Indigoids: Are a group of vat dyes with a similar chemical structure to that of indigo, from which it derives its name. Once these dyes are extracted from the plant (indigo) or shell fish (murex)*, the dye is insoluble in water and is applied with vat reduction process.
Gallotannins: are a group of tannins that are a compound of tannic acid and ellagic acid combined with sugars. They are usually colorless or yellow. Eg. Gallnut, sumac, myrobalan and pomegranate.
Condensed tannins: are a group of tannins that are compounds of cathechin or flavan. They are brown or reddish brown and can be used as dyes. E.g. Cutch, Quebracho and chestnut.
*Tyrian Purple is a pigment made from the mucus of one of several species of Murex snail. Production of Tyrian Purple for use as a fabric dye began as early as 1200 BCE by the Phoenicians, and was continued by the Greeks and Romans until 1453 CE, with the fall of Constantinople. It is a secretion produced by several species of predatory sea snails in the family Muricidae, rock snails originally known by the name 'Murex'. In ancient times, extracting this dye involved tens of thousands of snails and substantial labor, and as a result, the dye was highly valued. ( image source: wikipedia)