Vegetal Dyes

Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources— roots, berries, bark, leaves, and wood—and other biological sources such as fungi.

Archaeologists have found evidence of textile dyeing dating back to the Neolithic period. In China, dyeing with plants, barks and insects has been traced back more than 5,000 years.Goodwin (1982), p. 11. The essential process of dyeing changed little over time. Typically, the dye material is put in a pot of water and heated to extract the dye compounds into solution with the water. Then the textiles to be dyed are added to the pot, and held at heat until the desired color is achieved. Textile fibre may be dyed before spinning or weaving ("dyed in the wool"), after spinning (" yarn-dyed") or after weaving ("piece-dyed"). Many natural dyes require the use of substances called mordants to bind the dye to the textile fibres. Mordants (from the Latin verb 'mordere', meaning 'to bite') are metal salts that can form a stable molecular coordination complex with both natural dyes and natural fibres. Historically, the most common mordants were alum (potassium aluminum sulfatea metal salt of aluminum) and iron ( ferrous sulfate). Many other metal salt mordants were also used, but are seldom used now due to modern research evidence of their extreme toxicity either to human health, ecological health, or both. These include salts of metals such as chrome, copper, tin, lead, and others. In addition, a number of non-metal salt substances can be used to assist with the molecular bonding of natural dyes to natural fibreseither on their own, or in combination with metal salt mordantsincluding tannin from oak galls and a range of other plants/plant parts, "pseudo-tannins", such as plant-derived oxalic acid, and ammonia from stale urine. Plants that bio-accumulate aluminum have also been used, including club mosses, which were commonly used in parts of Europe, but are now endangered in many areas. The '' Symplocos'' genus of plants, which grows in semi-tropical regions, also bioaccumulates aluminum, and is still popular with natural dyers. Some mordants, and some dyes themselves, produce strong odors, and large-scale dyeworks were often isolated in their own districts.

Throughout history, people have dyed their textiles using common, locally available materials, but scarce dyestuffs that produced brilliant and permanent colors such as the natural invertebrate dyes, Tyrian purple and crimson kermes, became highly prized luxury items in the ancient and medieval world. Plant-based dyes such as woad ('' Isatis tinctoria''), indigo, saffron, and madder were raised commercially and were important trade goods in the economies of Asia, Africa and Europe. Across Asia and Africa and the Americas, patterned fabrics were produced using resist dyeing techniques to control the absorption of color in piece-dyed cloth. Dyes such as cochineal and logwood (''Haematoxylum campechianum'') were brought to Europe by the Spanish treasure fleets, and the dyestuffs of Europe were carried by colonists to America.

The discovery of man-made synthetic dyes in the mid-19th century triggered a long decline in the large-scale market for natural dyes. Synthetic dyes, which could be quickly produced in large quantities, quickly superseded natural dyes for the commercial textile production enabled by the industrial revolution, and unlike natural dyes, were suitable for the synthetic fibres that followed. Artists of the '' Arts and Crafts Movement'' preferred the rich, complex colors of natural dyes, since many natural dye sources contain more than one type of dye compound, unlike synthetic dyes which tend to rely on a single type of dye compound, creating a flatter visual effect. This helped ensure that the old European techniques for dyeing and printing with natural dyestuffs were preserved for use by home and craft dyers. Natural dyeing techniques are also preserved by artisans in traditional cultures around the world.

In the early 21st century, the market for natural dyes in the fashion industry is experiencing a resurgence. Western consumers have become more concerned about the health and environmental impact of synthetic dyeswhich require the use of toxic fossil fuel byproducts for their productionin manufacturing and there is a growing demand for products that use natural dyes. The European Union, for example, has encouraged Indonesian batik cloth producers to switch to natural dyes to improve their export market in Europe. While historically, dyers possessed sophisticated knowledge of natural sources of true dye compounds, nowadays the internet contains a lot of inaccurate information about sourcespredominantly foodsthat are not supported by the historic record or by modern science. In natural dyeing, there are "fast" dye compounds (those that have the necessary molecular structure to form stable chemical bonds with mordants and fibres, and so provide good resistance to fading when washed, exposed to light, or subjected to normal rubbing/abrasion; these are found throughout the historic record), and there are "fugitive" compounds, which are not true dyes (those that fade and wash out quickly, as they lack the molecular structure to form stable bonds, or any bonds at all, to mordants and fibres). Mordanting can not fix fugitive sources to fibres. Fugitive sources include nearly all berries, red cabbage, beets, spinach, black beans, most flowers (though some important true dyes are flower derived) and many others.

Dyes in use in the fashion industry

Because of their different molecular structure, cellulose and protein fibres require different mordant treatments to prepare them for natural dyes.
* Cellulose fibres: cotton, linen, hemp, ramie, bamboo, rayon
* Protein fibres: wool, angora, mohair, cashmere, silk, soy, leather, suede

Cellulose fibres have a lower affinity for natural dyes than do protein fibres. The most common method for preparing cellulose fibres is to use a tannin first (tannins have high affinity for both protein and cellulose fibres), then use an aluminum metal salt. The most common method for preparing protein fibres is to use alum. However, the historic record contains many hundreds of different mordanting methods for both protein and cellulose fibres.

The types of natural dyes currently popular with craft dyers and the global fashion industry include:

Animal-derived dyes

* Cochineal insect (red)
* Cow urine (Indian yellow)
*Lac insect (red, violet)
*Murex snail (purple, indigo blue)
*Octopus/Cuttlefish (sepia brown)

Plant-derived dyes

* Catechu or Cutch tree (brown)
* Gamboge tree resin (dark mustard yellow)
*Chestnut hulls (peach to brown)
* Himalayan rhubarb root (bronze, yellow)
* Indigofera leaves (blue)
*Kamala seed pods (yellow)
*Madder root (red, pink, orange)
* Mangosteen peel (green, brown, dark brown, purple, crimson)
*Myrobalan fruit (yellow, green, black, source of tannin)
* Pomegranate rind (yellow)
* Teak leaf (crimson to maroon)
* Weld herb (yellow)
* Juglans Nigra or Black Walnut hulls (brown, black, source of tannin)
* Rhus typhina or Staghorn Sumac tree (brown, source of tannin)

Origins

Colors in the "ruddy" range of reds, browns, and oranges are the first attested colors in a number of ancient textile sites ranging from the Neolithic to the Bronze Age across the Levant, Egypt, Mesopotamia and Europe, followed by evidence of blues and then yellows, with green appearing somewhat later. The earliest surviving evidence of textile dyeing was found at the large Neolithic settlement at Çatalhöyük in southern Anatolia, where traces of red dyes, possible from ochre (iron oxide pigments from clay), were found.Barber (1991), pp. 223–25. Polychrome or multicolored fabrics seem to have been developed in the 3rd or 2nd millennium BCE. Textiles with a "red-brown warp and an ochre-yellow weft" were discovered in Egyptian pyramids of the Sixth Dynasty (2345–2180 BCE).Rogers, Penelope Walton, "Dyes and Dyeing". In Jenkins (2003), pp. 25–29.

The chemical analysis that would definitively identify the dyes used in ancient textiles has rarely been conducted, and even when a dye such as indigo blue is detected it is impossible to determine which of several indigo-bearing plants was used. Nevertheless, based on the colors of surviving textile fragments and the evidence of actual dyestuffs found in archaeological sites, reds, blues, and yellows from plant sources were in common use by the late Bronze Age and Iron Age.

In the 18th century Jeremias Friedrich Gülich made substantial contributions to refining the dyeing process, making particular progress on setting standards on dyeing sheep wool and many other textiles. His contributions to refining the dyeing process and his theories on color brought much praise by the well known poet and artist Johann Wolfgang von Goethe.

Processes

After mordanting, the essential process of dyeing requires soaking the material containing the dye (the ''dyestuff'') in water, adding the textile to be dyed to the resulting solution (the ''dyebath''), and bringing the solution to a simmer for an extended period, often measured in days or even weeks, stirring occasionally until the color has evenly transferred to the textiles.

Some dyestuffs, such as indigo and lichen