The Art and Craft of Natural Dyeing

by J.N.Liles

This excerpt is from The Art and Craft of Natural Dyeing: Traditional Recipes for Modern Use by J.N. Liles. Copyright © 1990 by The University of Tennessee Press. Used with permission.

Fermentation Vats

These vats are the oldest and were in use at least from 2000 B.C. to, in a few instances, the present (traditional dyers of Japan, possibly isolated areas in Nigeria, and some contemporary dyers still use fermentation vats). Their use decreased markedly for cotton and linen when the copperas vat became available (1750), and for wool when the hydrosulfite vat became available (about 1880).

All natural fibers may be dyed in fermentation vats, but they are generally more suitable for the dyeing of wool than for linen, silk, and cotton. One reason is that they must be warm to work well, and another is that they are generally weaker with respect to reduced indigo. The cotton dyer of old, especially, had to rely on many dips, up to fifty in some cases over several days, to obtain a very deep blue. Of course, with such a large number of dips, the color would be very, very permanent. The weaker vat was more difficult and time­consuming for the various forms of tie, stitch, or fold dyed work as well.

Fermentation vats rely on bacterial or yeast fermentation to reduce the vat (remove oxygen and reduce the indigo blue to soluble indigo white), and ammonium hydroxide (ammonia) and ammonium carbonate or lime water or wood ash lye (weak potassium hydroxide and carbonate) to dissolve the reduced indigo. In virtually all cases, alkali and reducing agent are minimal in the working vat. Thus, the worry of excess alkali or reducing agent is minimal.

Fermentation vats, though somewhat slow and requiring considerable expertise and attention, were responsible for all of the fine indigo blue found on existing wool specimens dyed prior to about 1880 and much later in certain places. They were eventually replaced by the hydrosulfite vat. Fermentation vats were also used in some places rather late for cotton and linen as well (Nigeria, etc.) but were mostly replaced by the copperas vat (1750) or the zinc­lime vat (1845).

All fermentation vats have a smell, the urine vats generally being the worst. Thus, it is suggested that they be set up and used during summertime when they may be kept outside in the sun. Under these circumstances the proper temperature may be more easily maintained and the smell kept outside.

The alkali of the urine vat (ammonia, ammonium hydroxide, and ammonium carbonate) is the least damaging of all alkaline substances to wool, and for this reason buyers of indigo­dyed woolen yarns and woolen articles often would not purchase such items if they did not smell right (the stale urine odor reminiscent of an old­fashioned diaper pail or privy does disappear eventually). This attitude prevailed in some places long after the introduction of the hydrosulfite vat. And it is dismaying to find that cheating occurred everywhere, as I recently discovered in the following:

The typical indigo smell which adheres to all dyeings produced on the fermentation vat, may also be produced artificially by the addition of Vat Odour N. This is a volatile perfume which is applied by spraying the finished goods with the solution, or by turning the dyed goods in a cold bath containing about 1 1/2 ounces of Vat Odour N, dissolved in 2 pints alcohol, in 100 gallons water. The preparation may also be added to the finishing paste. Subsequently the goods so treated are dried not too quickly.[Manual for the Dyeing of Cotton and other Vegetable Fibres, 221]

Note that no mention was made concerning the composition of Vat Odor N.

The question may arise as to why the craftsperson should learn to use the fermentation vat at all when the lye­hydrosulfite vats or the zinc­lime vats are much more easily set and managed. Five reasons come to mind: some shades are obtainable only with a fermentation vat; materials such as wool fleece and cotton lint may be left for extended periods (several hours to one to two days) in such a vat, generally producing a fine and quite permanent color; once working, a fermentation vat may operate for several days with little attention; building shade (over time) generally works well in the fermentation vat because the amounts of alkali and reducing agent are generally optimal; and, finally, it is gratifying to be able to reproduce a method having such historical significance. As previously stated, all existing museum specimens dating from at least 2000 B.C. to 1750, and much later in many cases, were done in fermentation vats.

Perhaps the urine vat is the easiest fermentation vat to start with (on a small scale) because it often works with no additions whatsoever except indigo and urine. Urine contains nutrients for bacterial fermentation which reduces the indigo, and the bacteria also convert the nitrogenous waste product (urea) into ammonia (ammonium hydroxide and carbonate), the alkali which dissolves the reduced indigo white.

Which type of urine is best? This was the subject of considerable debate in the old days, with many "experts" contending that urine from diabetics and drunkards was generally best. This conclusion has scientific credibility; urine from untreated diabetics is high in urea and volume, and contains blood sugar (glucose or dextrose), an additional nutrient for bacterial or yeast growth. Alcohol and its breakdown products can also serve as nutrients for microorganisms. Urine from small boys and pregnant women was also considered very good. In the case of pregnant women, at least, there are probably additional nutrients and urea produced by the developing fetus.

Actually, any urine, such as is produced by normal eating and drinking habits, will do. This will amount to from 1/2 to 1 1/2 quarts per day. It is unsound to embark on a high liquid intake in order to produce the desired quantity of urine faster. This idea is an old one. I recently read an account of a 19th-century English woman who would invite all of her husband's men friends over for an evening of card playing and strong cider drinking whenever she wished to set a reasonably large urine vat. This resulted in some amusement, with neighbors commenting that "Madame so and so" was having another of her "piddle parties." The reason the method is unsound is that the adult body produces and releases into the urine approximately 3 grams (1/9 ounce) of urea per day whether this amount be released in 1/2 to 1 1/2 quarts of urine or in three to four quarts of urine. Therefore, the nutrient concentration will be low per unit volume in the dilute urine.

It is suggested, however, that vitamin and mineral intake be increased several days prior to collection in that excesses of these materials (B-complex vitamins, vitamin C, and minerals) are excreted in the urine. Increasing protein intake one or two days prior to and during the collection period will increase both urea production and volume of urine, thus shortening the collection period as well. The reason for this is that excess ingested protein is not stored in the body; instead the excess amino acids from the protein are deaminated (the amino group is removed and converted to urea), and increased urea removal by the kidneys is accompanied by additional water loss.

It is also strongly suggested that some thought be given as to where to store the urine during the collection period. My first experience proved somewhat embarrassing from this lack of foresight. I had collected about 2/3 of a gallon in a white plastic milk jug, and hoping to accelerate the transformation of some of the urea to ammonia, set the jug out in the sun next to the garage. Somewhile later, one of my sons decided to cut the grass, and upon finding an empty gas tank, reached for the nearest source of what appeared to be gasoline. He poured at least a quart of the liquid into the tank before the odor reached his nostrils!

Sig (Urine) Vat No. 1 (Sig Vat, "Good Old Sig Vat," Chamberley Vat)

It is suggested that, initially a one­ to three­gallon vat be attempted since this may be set up in a strong wide­mouth glass jar or white plastic container (to better observe the color change from blue to green or yellow­green as the vat comes to order).

1. Collect the desired volume of urine.

2. Make a little bag of the finest mesh material on hand and place 1/2 to 1 ounce of natural indigo (two to six tablespoons) within. Tie the bag shut and drop it into the vessel or suspend it just below the surface tied by a string to a stick laid across the top of the vessel.

3. Place the vessel in a warm place or in the sun (in the old days, in cold weather, the vessel was placed on the hearth next to the fire). Natural fermentation should start within a couple of days. Also, night and morning, rub the bag of indigo between the fingers to release into the vat the indigo blue. Eventually, all of the indigo fine enough to reduce will be released.

4. If all goes well, in a few days, depending largely upon temperature, the vat color will change from blue to green or greenish-yellow, at which time it is fit to use.

Dyeing Procedure:

1. If little sediment is present, well scoured and wetted­out articles may be placed directly in the vat; otherwise they should be suspended or dipped. An exception is wool fleece or cotton lint which may be introduced, uncrowded, in a plastic mesh bag, such as those used for onions or oranges. Immersion time can be a few minutes to several hours to one or two days. Air the material as for other indigo vats, redip for heavier shades, and finish off as with the lye-hydrosulfite vat.

2. Watch the color of the vat carefully and add no more air than absolutely necessary when adding or removing materials from the vat.

3. Add more urine as evaporation occurs. This replenishes both nutrients and urea, which the ferments use up. Also add more indigo as time passes. This vat may be used for some time.

A fermentation vat is a "chemical balancing act." On the one hand, the fermenting microorganisms produce the alkali (ammonia) from the urea, but at the same time they produce carbonic acid and reduce the indigo. Carbonic acid partially neutralizes the alkali, producing very weakly alkaline ammonium carbonate. Thus, if fermentation is too active, the indigo will be reduced, but there may not be enough alkali to dissolve it; i.e., the vat may remain blue and go sour. Of course, if fermentation is not active enough, little of the indigo blue will be reduced to indigo white.

Troubleshooting the Vat:

If the vat remains blue after several days have elapsed, the temperature may not be high enough to induce fermentation. Get the vat into the sun or into a warmer area. Add a little dry cake yeast, madder root, or dried woad, as the vat may not have become "seeded" with the proper microorganisms.

If fermentation has been heavy and the vat smells sour, add, cautiously, small amounts of clear liquid household ammonia. The alkali will decrease the growth rate (fermentation) of the microorganisms, supply the necessary alkali for the reduced indigo, and at the same time more than neutralize the acidity. In many instances urines contain approximately the appropriate amounts of nutrients and urea so that enough ammonia is produced to keep fermentation at the level of reducing the indigo, but not rapid enough to sour the vat.

Some indigoes, particularly synthetic indigoes, will not work in a fermentation vat. Apparently this is the result of chemicals used in the processing or production of the indigo which prevent fermentation.