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The Natural Dye Blues - Indigo Dye, Woad and Logwood
INDIGO DYE
Indigo dye is likely the most well known natural dye - the color of blue jeans - and refers to the blue matter extracted from indigo bearing plants, most commonly from Indigofera tinctoria which originates in Asia, India and South America. It reaches the market in a fine powder or pressed block which is insoluble in water. World consumption of indigo in the 1800s was very large, so in 1866 a German chemist named Adolph von Baeyer began his studies of the pigment and eventually elucidated its chemical structure so that it could be synthesized commercially. At the end of the 19th century, Germany was able to produce synthetic indigotine cheaper than the natural dyestuff, and thus Germany took charge of supplying indigo.
Indigo produces a colorless glucose based substance called indican. Fermentation breaks this glucose down to indigotin which is insoluble in water. It needs to be reduced, that is, the oxygen removed from the dye bath, to be used as a natural dye. Into this reduced form, fiber is immersed and when removed and allowed to oxidize, turns almost magically back to it's blue color. This process is referred to as vat dyeing. It is a fascinating process and does not require the use of mordants.
Aurora gives instructions for a traditional Natural Fermentation Indigo Dye Vat if you prefer not to use chemicals. Maiwa instructions are for the more common method using thiourea dioxide or sodium hydrosulfite and lye (sodium or potassium hydroxide). You can also find instructions for three different methods in Jenny Dean's excellent book Wild Colors. These are the hydrosulfite vat, the yeast vat and the urine vat (yes urine was a commonly used substance in ancient dyeing methods).
Navy Blue and Forest Green from Blue Castle Fiber Arts are Indigo based natural dyes but do not require the indigo dye vat method when used on wool or silk. Cellulose fibers, like cotton, linen or hemp do require natural indigo with the vat method.
Woad is derived from a plant, Isatis tinctoria, growing in the North of France and in England. The blue pigment in woad is the same as in indigo (Indigofera tinctoria) dye, but it is less concentrated. It was the only blue natural dye in the West before Indigo dye was introduced from India. Like indigo, it dyes fiber a greenish colour which changes to a deep blue in the air. It is said to be inferior in colour to indigo dye but the colour is more permanent. The fresh, young leaves when cut are reduced to a paste, kept in heaps for about fifteen days to ferment, and then are formed into balls which are dried in the sun. These balls are subjected to a further fermentation of nine weeks before being used by the dyer. There has to be a breakdown of indican, a sugar-bearing molecule, to the dyestuff indigotine.
LOGWOOD (Bois de Campeche, Campeachy Wood)
Logwood is a natural dye wood from Central America, used for producing blues and purples on wool, black on cotton and wool, and black and violet on silk. It is called by old dyers one of the Lesser Dyes because the colour was said to lose all its brightness when exposed to the air. But with proper mordants and with careful dyeing this natural dye can produce fast and good colours. The logwood chips should be put in a bag and boiled for 20 minutes to 1/2 an hour, just before using.
RECIPES for DYEING with LOGWOOD
BLACK Mordant the wool for 1 to 1-1/2 hours with 3 per cent Chrome and 1 per cent Sulphuric Acid. Wash and dye in separate bath for 1 to 1-1/2 hours with 50 per cent Logwood. This gives a blue black.
A dead black is obtained by adding 5 per cent Fustic to the dye bath.
A green black by adding more fustic. Also by adding 3 to 4 per cent Alum to the mordanting bath a still greener shade can be obtained.
A violet black is produced by adding 2 per cent Stannous Chloride (tin) to the dye bath and continue boiling for 20 minutes.
LAVENDER Mordant with 3 per cent Bichromate of Potash* for 45 minutes and wash. Dye with 2 per cent madder, 1 per cent logwood. Enter the wool, raise to the boil and boil for 45 minutes. The proportion of logwood to madder can be so adjusted as to give various shades of claret to purple.
A FAST LOGWOOD BLUE (Highland recipe.) Mordant with 3 per cent Bichromate of Potash* and boil wool in it for 1-1/2 hours. Wash and dry wool. Make a bath of 15 to 20 per cent logwood with about 3 per cent chalk added to it. Boil the wool for 1 hour, wash and dry. The wool can be greened by steeping it all night in a hot solution of heather till the desired tint is obtained.
DARK RED PURPLE WITH LOGWOOD Mordant with 25 per cent alum and 1 per cent cream of tartar for 1 hour. Let cool in the mordant, then wring out and putaway for 4 to 5 days.
Dye with 60 per cent logwood and 25 per cent madder. Boil up the logwood and madder in a separate bath and pour through a sieve into the dye bath. Enter the wool when warm and bring to the boil. Boil from 1/2 hour to 1-1/2 hours. Wash thoroughly in soft water.
PURPLE
Mordant wool with 25% alum and 3% tartar for one hour; wring out and put away in a bag for some days. Dye with 1/4 lb. logwood for 1 hour.
* Although Bichromate of Potash or Chrome is used in small amounts, it is considered a toxic substance.
