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Dyes And Mordants
I. Introduction and brief history of dyeing.
By 1630, human beings had been using plants, animals and minerals to change the natural color of plant and animal fibers for at least five thousand years. The oldest written record of dye use goes back to 2,600 BC in China, and archaeologists have identified dyed textiles from about 1,400 years earlier than that. Vastly more is known about commercial dyeing than is known about early modern home dyeing. That doesn't mean that a lot is known about either. Dyeing was considered as much an art as painting, and rarely was the process documented before the latter part of the eighteenth century. Major sources of information about dyeing prior to that date are two dyers manuals that were published in the fifteenth and sixteenth centuries, manuscripts containing dye recipes other than the dyers manuals and economic records of towns and guilds. Next to nothing is known concerning home-dyeing prior to the revival of natural dyeing in the 1960s.
The first European commercial dyer's guide, Mariegola Dell'Arte de Tentori, was published in the early fifteenth century. Earlier works mentioned dyestuffs, the dye industry, and an occasional dye recipe. For example, a Greek manuscript known as the Stockholm Papyrus contains a recipe for imitation purple, and an Egyptian papyrus of 236 BC mentions dyers. Pliny the Elder talks about dye plants and bleaching with sulfur. For the most part, however, actual dye recipes were rarely printed. Dyers considered themselves artists, and guarded their recipes carefully. Years of development could go into the formulation of a good black dye, for instance, which would put that dyer's goods in great demand. Since reproducing colors with natural dyestuffs is never easy, the dyer could be fairly certain to maintain his position of superiority as long as the recipe did not become known.
The earliest colors that rated mention by ancient writers were reds, purples and blues; all dyed using natural materials that are known today and were major dyestuffs until the discovery of the first synthetic dye in 1856. Other subjects that ancient writers mention indicate that techniques such as printed fabric and batik are hundreds, if not thousands, of years old, as well.
Two major events in the history of dyeing during the early seventeenth century were the discovery of the effects of the use of tin as a mordant in 1630 by a Dutch chemist, and the beginning of the East India Company's importation of calico from India in 1631. The discovery that the Indians were able to produce brilliant colors and fancy patterns on cotton resulted in a drive by European dyers to reproduce the effects.
A. Before the fact
Plant and animal fibers can be dyed in the fiber (raw), as yarn or as fabric. The process for preparing the fiber for dyeing varies only slightly for the different forms, but can vary quite a lot between fibers. Linen and silk were rarely dyed raw, due to the vagaries of processing these fibers. The natural color of most wool, stream-retted linen and silk is slightly yellow. Dew-retted linen is grayish. For the sake of simplicity, this article will refer throughout to fabric as the item being dyed. Also, please look to the glossary at the end for definitions of dyeing terms.
The first step in preparing the fabric for dyeing was scouring. For wool this meant washing in stale urine or a solution of potash and water to remove the natural oils still present, as well as any oils added during processing. Even where the wool had been scoured on the sheep or in the raw, dirt was inevitably picked up during the weaving and had to be removed before dyeing. The ammonia in the urine and potash mix acted as a detergent.
Silk had to be cleaned before weaving, as in its natural state it was coated with a waxy substance called sericine, which made the fiber sticky and gave it a harsh feel. The method was fairly simple: the silk was boiled in a soapy solution for a number of hours. The removal of the sericine took most of the yellow coloring with it. The same process was followed after weaving to remove whatever dirt and oils were acquired during processing.
Cotton and linen, which not only contained natural waxes but were often coated with sizing during weaving, were fermented by adding bran to warm water into which the fabric was packed. Weights held the fabric down during the fermentation process, and it was important to remove the fabric before the scum created during fermentation settled into the fibers.
Once the fabric was clean, it was time for bleaching. Cotton and linen were almost always bleached before dyeing as the bleaching process helped assure that the fiber or fabric would dye evenly. Wool and silk were generally only bleached if they were to be dyed a light color. "Black" wool, which could be any color from tan to dark brown, would be used in its natural state.
Silk and wool were bleached by means of sulfur fumes. The wet fabric would be hung in a special room with pots of sulfur set on the floor. The sulfur would be lit and the room sealed until the sulfur burned out. This process was much faster than the method used to bleach cotton and linen, but was considered less satisfactory because sulfur-bleached fabric tended to turn yellow if not carefully handled. In addition, this method of bleaching did more damage to the fibers. While it is unclear how old this method is, the Roman Pliny mentions the use of sulfur for bleaching.
Cotton, linen and hemp, all cellulose fibers, were bleached in basically the same way. The fabric would be soaked in a mildly alkaline solution (often made from "rotten urine" or potash dissolved in water), removed and rinsed, then spread out in the sun. Depending on the time of year, the fabric would be moistened by dew or by being sprinkled with water. After some time in the sun, the fabric would be rinsed again, soaked in a mildly acid solution (often sour milk), washed, then returned to another alkaline bath. This process of alkaline bath, sun exposure, acid neutralization and washing would be repeated eight or more times, depending on the degree of whiteness desired. The entire bleaching process could take as long as eight months to complete.
Now the fabric was ready to be dyed. The first step was to obtain the dye. Commercial dyers bought theirs in the form of cakes, dried plants or wood chips. Home dyers, on the other hand, would have to gather the plants, lichens or other materials. This meant they needed to know which parts of which plants would produce the colors they were striving for.
Next, the dyer needed to prepare the dyebath, either by boiling and straining plant matter or by grinding prepared dyestuffs. Commercial dyers needed to know how many pounds of dyestuff were needed to dye large amounts of fabric, and trusted to experience (and the sellers of the dyes) for that information.
While the dyebath was being readied, the fabric was prepared for dyeing. Since it was received by the commercial dyer already scoured and bleached, the only step necessary was mordanting. A mordant is a chemical (most commonly a metal salt) that helps the dye adhere to the fabric. Fabric could be mordanted before, during or after dyeing. Since fabric was never dyed dry, it was common to use a mordant bath to wet the fabric before dyeing.
Once the dyebath was ready, the wet fabric would be lowered into it. The fabric would be drawn repeatedly through the dye to insure that the color would take up evenly. When either the desired color was achieved or the dyebath was exhausted, the cloth would be removed, rinsed thoroughly, and dried. Some colors required the fabric to be dyed multiple times.
A. Equipment and requirements (tools, fuel, location)
The two most important requirements for a dye house were plenty of clean, soft water and plenty of fuel. The location of the dye house was determined by this need for water and fuel. Dyeing required so much fuel, in fact, that many localities tried to limit the amount of wood bought by the dyers, restrict where it could be purchased, or ban the use of certain types of wood.
Ideally, a dyehouse had both a well with a pump and a system of pipes and troughs, and a nearby river. Soft water was preferred, as the minerals in hard water could affect the dye colors and the ability of the fabric to absorb the dye. The river was often used for washing fabrics (before or after dyeing) with the aid of a "dyer's raft" anchored in the river. There is record in the Hamburg archives concerning a hearing held to determine whether the dyers should be permitted to anchor a new raft after the old one was swept away during a flood. The council listened to testimony from local fishermen about the deleterious effect of the raft on the fish population. In the end, a new raft was permitted, but the dyers were forced to move it down steam, past the fishing grounds.
In addition to water and fuel, the dyers needed copper vats for preparing dyebaths, wooden vats for dyeing the fabric, furnaces for heating the water and boiling the dyes, hooks, rods, barrows and winches to move the fabric around, tools for grinding the dyestuffs, the dyestuffs themselves, mordants, and a building large enough to use and store it all. The building had to have a stone floor with provision for draining water and separate rooms for drying wet fabric and for storage. The roof had to be vented to allow steam and fumes to escape. Often, there would be a separate shed for storing fuel.
Setting up a dye house was an expensive proposition. In Nuremberg during the middle of the sixteenth century, the city council ordered a dyehouse built, with estimated construction costs of three thousand guilders. This was part of a series of expenditures made by the council to lure dyers from Antwerp to Nuremberg. All told, the council's investment totaled more than ten thousand guilders.
Home dyeing was simpler. All that was necessary was a pot for preparing the dyebath and some utensils for handling the hot, wet fabric. The modern home dyer uses inert pots and utensils dedicated to dyeing. The early modern home dyer probably used iron pots; whether these were dedicated to dyeing is unknown. The wet cloth could be lowered into the dyebath by hand, but once there a spoon or paddle would be needed to swish the cloth about and insure the color was absorbed evenly. Useful, but not required, would be some type of roller or wringer to squeeze excess dyebath from the cloth when it was done. Lastly, a place was needed to hang the finished product where it would be protected from dirt and dust while it dried.
B. Dyestuffs and mordants
Dyestuffs could be found everywhere, but since most produced various shades of yellow and brown, those that produced reds, purples and blues were more valuable. After the discovery of the Americas in the fifteenth century and the establishment of the English East India Company in 1600, more exotic colors were available. Explorers were so aware of dyestuffs as trade goods that the country Brazil was named after the abundance of brazilwood found there. Not all the exotic dyestuffs were worth using, however. The red produced by brazilwood, for example, is fugitive, as is the lavender that comes from logwood.
The most common sources for reds, purples and blues during the early modern period were madder (red), murex (so called "imperial purple"), kermes (red), orchil (purple), woad (blue) and indigo (blue).
During the period between 1624 and 1627 in Frankfurt am Main, the cost of various dyestuffs ranged from about seven guilders per hundredweight for madder to two hundred and twenty guilders per hundredweight for indigo from Dominique. Between those two extremes, prices are recorded for galls from Aleppo at twenty-four guilders per hundredweight, woad from Erfurt at sixty guilders per barrel (approximately sixty pounds) and cochineal from Poland at about nine guilders per pound. Thus, it is clear that the price of the various dyestuffs varied widely.
The most expensive colors were black, blue and dark green, all of which required bottoming with woad or indigo first. The highest quality blacks were produced by "bottoming" fabric with woad until it was a very dark blue, then overdyeing it with madder. This combination made a color very close to a true black. Blue used woad or indigo alone, and dark green was produced by overdyeing blue fabric with weld, dyer's greenweed or a similar yellow dye.
Cheaper methods did exist to produce dark colors. Galls mixed with iron filings made black, black walnut shells produced a good brown, yellow bedstraw and safflower (when prepared as a vat dye) produced red. The home dyer may have experimented with reds and purples from beets and berries, too. Unfortunately, time has shown that these last produce only fugitive colors. Some of the colors produced by these cheaper methods were as good as the more expensive dyestuffs. Some, however, were not. Dyes containing too much tannic acid or iron damaged the fabric, eventually causing the fabric to disintegrate. Safflower red, like the berry colors, was fugitive.
Dyes such as galls, sumac, vitriol were banned in many cities and called "devil's colors" because of the damage they did to the fabric. As a measure to protect the woad trade, indigo also appeared in most lists of "devil's colors," even though it did not damage the fabric and, in fact, was a more efficient dye than woad.
In fact, most dyes were fugitive without the assistance of a mordant. Most mordants are metal salts, although there are a few, like tannic acid and tartartic acid, that are not. During the early modern period, the most common mordants were alum, copperas (iron) and blue vitriol (copper). All of the metal-salt mordants were toxic to some degree. Disposal of mordant baths and spent dye liquor into the nearest river led to fish kills and unnaturally colored streams.