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Silk Dyeing

Page history last edited by Liz Johnson 11 years, 11 months ago


Dyeing silk


by Cor Snabel and Elizabeth A. Johnson




Dyeing silk was a highly specialized craft, very different from dyeing any other material. Silk was obtained from the cocoons of silkworms, which contained a natural glue called sercine. After it was unwound from the cocoons and spun into thread, the raw material was a bit yellow and rather stiff. Before the dye could stick to the silk, it needed washing to remove the sercine. Putting it into a boiling soap solution removed the glue, made the silk white, and gave it its smooth softness.



The washing


Before washing, the skeins of silk thread were put into linen bags, each of which could contain 25 to 30 pounds of silk. This was done to prevent the silk threads from burning to the bottom of the kettle.


The amount of soap used in the washing procedure depended on the color that the dyer or his customer wanted for the end-product. All of the silk was first washed for four hours in a bath of 20 pounds of soap per 100 pounds of silk. After the first round, thread intended for each particular color underwent another washing procedure in its own specific soap solution, in a bath which could last up to four or five hours.


After the final washing, the silk was removed from the linen bags. For many colors it had to be put in a bath of aluminum sulfate. This salt allowed the dye to stick to the fabric making it permanent.



The dyeing


The dye was mixed in a large square kettle. When it was ready to be used, long sticks were put through the skeins of silk. These sticks were put on top of the kettle, allowing the strings to hang into the dye. The sticks were turned constantly so the silk was evenly dipped into the dye, until all the threads evenly took on the desired color.


The dyer knew a great variety of colors in all of their nuances, and he knew how to obtain many slight differences from various dyestuffs. White was not just white; basically he used five kinds of white: Chinese white, Indian white, Milk white, Silver white and Blue white. Blue had the same variety: Pale blue, Sky blue, Middle blue, Kings blue and Turkish blue. It would take too long to describe all the colors and their dyeing procedures, so this description will be limited to some basic colors.




If a bright white was required, the silk had to be washed twice in a soap solution of 30 pounds of soap per 100 pounds of silk. During this boiling process, indigo was added to give it extra brightness. For the very highest grade of whiteness, the silk was put in a sealed room in which sulfur was burned. For eight hours, the silk was exposed to the fumes of the sulfur. One to two pounds of sulfur was enough the give 100 pounds of silk the desired brightness.




For the color blue, the silk-dyer used eight pounds of indigo, six pounds of very pure potash, two pounds of madder, and eight pounds of bran. The bran was washed so it would be free of flour, and it was put on the bottom of the kettle. In another kettle, the madder and potash were cooked for 15 minutes. The indigo, which had been soaking in warm water for two days, was crushed in a mortar until it became a smooth paste that could be mixed with the other ingredients and poured onto the bran. After this mixture was stirred thoroughly, it was allowed to cool to a lukewarm temperature. When it turned a little greenish, it was stirred again and left alone for 3 or 4 hours. Then it was ready for use as a blue dye.


Silk that was to be dyed blue did not need the aluminum sulfate bath, because the indigo already contained enough salts to allow the threads to absorb the dye.




In order to produce yellow dye, the dyer mainly used the roots of the mignonette (reseda luteola) plant. For each pound of silk he needed two pounds of this plant. It was cooked for twenty minutes, then filtered through a sieve into another tub. After this solution had cooled to lukewarm, it was ready to be used.




The rocou plant was used to make the color orange. Originating in the Caribbean the Rocou plant was called "bija" by early Caribbean Indians, thus the plants's current scientific name: Bixa. Its crimson seeds were crushed together to make a red body paint that had a religious and magical significance to many tribes. To be used as a dye, rocou had to be dissolved in alkaline salt, such as potash. Thus, silk to be dyes with rocou did not need a prior bath in aluminum sulfate. If silk immersed in rocou solution turned red, that meant more potash should be added.




This color was derived from Cochineal, which was the dried scale-insect Coccus cacti, which lived on certain of the cactus plants of Mexico and elsewhere. Once the Cochineal had cooked, one ounce of cream of tartar and one ounce of tin were added per pound of Cochineal, to make the color a bit more yellow.


There was a second way to produce the carmine color. That was a process similar to the way orange dye was made from the rocou plant. The only problem was that the use of cream of tartar as a color enhancer did not have that same amazing effect as it had with Cochineal. Some dyers had found a solution for that by using white oak galls, which had about the same effect. Oak galls also produced an extra softness, similar to what cream of tartar could give to the silk.




Although the use of the oak galls produced good color, it had one big disadvantage: it gave the silk an overweight between 3 and 8 pounds per 100 pounds of silk. And because silk was sold according to its weight, much potential for trouble existed in many stages of the dyeing process.


In dyeing black there was also the alternative of using oak galls. Over the years silk dyers were often accused of expanding their profits by withholding some of the original material, for which loss of weight they compensated by adding these kinds of products, or even extra sugar or gum Arabic.






De Zijdeverwer, by J.P. Kasteleijn, 1791. Library of the Technical University in Delft.




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© 2008, Cor Snabel and Elizabeth A. Johnson

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