Atlas mondial des teintures naturelles

Indigo is the king of natural dyes. Unlike most plant colorants, it requires no mordant: the indigo pigment (indigotin, C.I. Natural Blue 1) fixes through a unique reduction-oxidation process. The leaf is fermented in an alkaline vat (lime or potash vat), reducing indigotin into soluble leuco-indigo. The fabric is dipped in this yellow-green solution, then oxidizes in the air and turns blue. Each successive bath deepens the color: 5 to 30 immersions depending on the desired intensity. Japanese indigo (ai-zome) from Persicaria tinctoria is considered the most luminous. Lightfastness is excellent (6/8 on the wool scale), washfastness is very good (4/5), but dry rubbing remains moderate (3/5 due to crocking). Denim jeans get their color from synthetic indigo, but artisan dyers prefer natural extraction for its depth and unique nuances.

Cochineal (Dactylopius coccus) is a parasitic insect of the prickly pear cactus (Opuntia), whose dried females contain 17-24% carminic acid (C.I. Natural Red 4). It takes about 70,000 insects to produce 500 g of dried dye. Peru supplies 85% of global production. With an alum mordant, a brilliant carmine red is obtained. Iron yields deep purples, tin yields brilliant oranges, and chrome yields dark bordeaux. On wool mordanted with alum, cochineal offers washfastness of 4/5 and rubfastness of 4/5. Lightfastness (5/8) is superior to most plant-based reds. Carminic acid is also used as a food colorant (E120) and in cosmetics, attesting to its safety. Pre-Columbian Aztec and Maya civilizations cultivated it as a precious commodity, and its export to Europe financed the Spanish Empire.

Madder (Rubia tinctorum) is the source of the famous "Turkey red," obtained through a complex multi-step mordanting process involving oil, alum, tannin, and lime. The dried root contains over 35 dye molecules, including alizarin (C.I. Natural Red 8) and purpurin. Alizarin was the first natural dye to be reproduced synthetically (1869, Graebe and Liebermann), almost entirely displacing madder cultivation. Today, artisan dyers are rediscovering roots aged for 3 years for deeper reds. Fastness is remarkable: 6/8 to light, 4/5 to washing, especially with the full Turkish process on cotton. The red trousers of the French army (1829-1915) were dyed with madder from Avignon.

Weld (Reseda luteola) is the most lightfast plant-based yellow in the entire natural dye palette: 7/8 on the wool scale (ISO 105-B02), surpassing even some synthetic yellows. Its main colorant, luteolin (C.I. Natural Yellow 2), forms an extremely stable aluminum-luteolin complex with alum. Cultivated in Europe since the Bronze Age, it was the basis of all medieval greens (overdyeing weld + indigo = "Lincoln green"). The whole plant (stem, leaves, flowers) is used. Yield: 15-20 g of dye per 100 g of wool. Combined with iron, it produces deep olives and khakis. It is the yellow dye most recommended by the CRITT Horticole for textile applications requiring high fastness.

Logwood (Haematoxylum campechianum) is the only natural source of deep blacks and violets. Its main colorant, hematein (C.I. Natural Black 1), forms almost black complexes with iron, and intense violets with chrome. The Spanish seized the Yucatan Peninsula partly to control this trade. Fastness is moderate without post-treatment, but modern fixation techniques (pre-tanning with iron + heat treatment) significantly improve durability. Historically used for mourning clothes, cassocks, and black uniforms. Still used today in histology (H&E staining).

Walnut hull (the green husk of the walnut fruit, Juglans regia or nigra) is a substantive dye: it bonds directly to fibers without a mordant thanks to juglone (5-hydroxy-1,4-naphthoquinone, C.I. Natural Brown 7) and tannins. It is one of the easiest and most durable dyes. Fresh hulls yield the richest browns. Lightfastness is excellent (6/8), washfastness very good (4/5). American black walnut (J. nigra) produces deeper shades than the common European walnut. Used since Roman antiquity to dye hair (Latin patricians), wools, and wood. At Misciano, we use walnut hulls from Dordogne for our linen pieces.

Saffron (stigmas of Crocus sativus) is the most expensive natural dye in the world: 150,000 flowers for 1 kg of dried saffron, 5-15 EUR/g. Its main pigment, crocin (C.I. Natural Yellow 6), produces a bright, warm yellow-orange. Historically reserved for Buddhist monks' robes and Persian royal garments. Lightfastness is low (3/8 light, 3/5 wash), limiting its textile use to ceremonial pieces rarely exposed. Iran produces 90% of the world's saffron. Despite its tinctorial fragility, no synthetic dye exactly reproduces the luminous warmth of natural saffron yellow.

Turmeric (Curcuma longa) yields the brightest, most immediate yellow of the entire natural palette: simply dipping the fabric in a rhizome decoction produces a vibrant yellow within minutes. Its pigment, curcumin (C.I. Natural Yellow 3), is highly soluble and dyes intensely. However, it is one of the least colorfast dyes: 2/8 in light (it fades quickly in the sun) and 2/5 in washing. In India, it traditionally dyes wedding saris and ceremonial garments. Mixed with indigo, it produces greens. With an iron mordant, it yields olives. Despite its fragility, it remains widely used in artisanal dyeing for its ease of use and negligible cost (2-5 EUR/kg).

Dyer's woad (Isatis tinctoria) was Europe's source of indigo before the importation of Asian Indigofera in the 16th century. The Lauragais region (Albi-Toulouse-Carcassonne triangle) grew enormously wealthy thanks to woad in the 15th century, giving rise to the famous townhouses of Toulouse. The same pigment (indigotin) is present but in lower concentration: 0.2-0.5% versus 2-4% for Indigofera. The blues obtained are softer, more luminous, with a characteristic gray-blue tone. Lightfastness is identical to tropical indigo (6/8 light, 4/5 wash). Woad is experiencing a revival in France, with organic cultivation in the Tarn and artisanal cosmetics brands.

Pomegranate rind (Punica granatum) is a remarkable dyer thanks to its high content of ellagic tannins (25-28%). It serves simultaneously as a colorant (golden yellows, khakis) and as a natural mordant for other dyes. With alum, it yields a warm golden yellow. With iron, deep grey-greens. With alum plus an indigo overdye, intense greens. Fastness is excellent: 6/8 light, 4/5 wash. In India, it has been used for thousands of years in the block-print (ajrakh) tradition of Gujarat. Its yield is very good: 50 g of powder per 100 g of fiber is enough for saturated shades.

Onion skin (Allium cepa) is the ideal entry point into natural dyeing: free, abundant, and yielding immediate results. Brown skins give golden oranges, red skins give warm pinks. The main colorant is quercetin (C.I. Natural Yellow 10), a flavonoid present at 2-5% in dried skins. With alum, luminous golden yellows are obtained. With iron, olive greens and browns. The yield is good: 100 g of skins per 100 g of fiber. Fastness remains moderate (4/8 light, 3/5 wash), but sufficient for artisanal interior pieces or scarves with limited exposure.

Lac is a resin secreted by the insect Kerria lacca on the branches of tropical trees in India and Southeast Asia. The dye extracted from this resin, laccaic acid (C.I. Natural Red 25), yields crimson reds and pinks of a richness comparable to cochineal, at a significantly lower cost. India produces 80% of the world's lac. It was traditionally used to dye the silks of saris and Persian carpets. Fastness is good: 5/8 light, 4/5 washing on alum-mordanted wool. Lac is also the raw material for shellac, used in varnishes and cosmetics.