The Indian Vat.—This presents much analogy to the woad vat, as the fermentation of vegetable matters effects the transformation of the indigo-blue. According to Dr. Calvert, the Indian vat, probably so called from its origin in the East, is taking the place in England of the old woad vat for dyeing wool and woollens. He describes its preparation as follows: 8 lbs. of powdered indigo is added to a bath containing 3½ lbs. of bran, 3½ lbs. of madder, and 12 lbs. of potash, which is maintained for several hours at a temperature of 200° F. It is then allowed to cool to 100° F., when fermentation ensues. After about forty-eight hours the indigo is rendered soluble, being reduced by the decomposition of the sugar and other products contained in the bran and the madder root during the process of fermentation. The distinguishing feature of this vat is the use of potash. The Indian or potash vats are spoken of by the best authorities as more easy to manage than the woad vat. They are less subject to accidents, and yield their coloring material more readily to the fibre, while three times as much wool can be dyed in the same time. On the other hand, they do not last so long, and require to be renewed at the end of twenty-five or thirty days. Besides, the fibres dyed in the potash vat have a darker shade than those dyed in the woad vat, owing to the large quantity of the coloring matter of the madder dissolved by the potash, which becomes fixed on the stuff with the indigo-blue.
The Urine Vat, but little used except for domestic dyeing, is founded upon the same principles as the other fermenting vats. This excretion, when putrefied, contains at the same time the nitrogenized principles which work as ferments and the alkali in the form of ammonia necessary for dissolving the indigo.
According to Dr. Calvert, improvements have been made of late years in the fermenting indigo vats by which the expense of madder is avoided. They are now prepared by adding to water, at a temperature of 200° F., 2 buckets of bran, 26 lbs. of soda crystals, 12 lbs. of indigo, and 5 lbs. of slacked lime. After five hours the bath is allowed to cool to 100° F., when fermentation ensues, and the indigo is dissolved in the alkali. This is, in fact, the German vat, soda taking the place of the potash, and the only fermenting material consisting of bran.
The German Vat is largely used by the dyers in the north of France, and is considered as more advantageous than the Indian vat, because the employment of soda is more economical than that of potash, while the vat can be maintained as long as two years. The vats used by them are prepared as follows: The water is heated to a temperature of 95°, and receives 20 pails of bran, 11 kilograms (about 24 lbs.) of crystals of carbonate of soda, 5.5 kilograms (11 lbs.) of indigo, and 4½ lbs. of slacked lime. After twelve hours, the temperature having been kept at 40° or 50°, fermentation commences, the liquid becomes of a greenish blue color, and disengages bubbles of gas. Indigo, soda, and lime are put in from time to time in the proportions above indicated, and also from six to eight pounds of molasses. At the end of the third day the vat is fit for use.
M. de Kæppelin, writing in. 1864, informs us that the reduction of indigo by means of molasses, is at present largely employed in the great establishments for dyeing woollen cloth at Sedan, Louviers, and Elbœuf.
The vat used is of very large dimensions, and from twenty-two to twenty-six pounds of indigo are dissolved in it; an equal weight of molasses is used, and three or four times the same weight of potash made caustic by a proportionate addition of lime.
The space reserved for this subject in our present paper will not permit us to enter upon a description of the processes used in the American dye-houses. This, as well as the applications of indigo in printing, and the uses of sulphate of indigo, must be deferred to another number.
Let us, in concluding the first part of our paper, at the risk of repetition, bring out in bolder relief a statement which presents the philosophy of all the various processes of the indigo vat, and at the same time, a conclusive argument for the use of this material, in preference to all cheaper substitutes. Indigo cannot enter into a fibre until it is dissolved. It cannot be dissolved so long as it is in a blue state. When reduced by any of the processes above described to the white state, it is easily dissolved, and can enter the pores of the fibre. Upon exposure to the oxygen of the air it takes up an equivalent of oxygen; it returns to the blue state, and, being then insoluble, it cannot be washed away from the fabric, and being saturated with oxygen it cannot be changed by air or light. This theory of the application of indigo involves a lesson to manufacturers, dealers, and consumers, especially of woollen fabrics. The theory, as well as experience, dating back to the dawn of the textile arts in the East, establishes that this material is incalculably superior to any other, in permanence at least, for imparting to woollen fibre a blue color, or as a foundation for most of the darker colors. By far the largest proportion of all cloths are of dark colors,—blue, black, green, brown, gray, or mixed,—and can advantageously receive in all or a portion of the fibre constituting them a direct dye or bottom for other dyes from indigo. It may be safely stated that, as a whole, no cloths in the world are manufactured from such good wool as those produced in the United States. We might expect that the shoddy goods of Yorkshire should be further falsified by fugacious dyes; but is it not a shame that our admirable wool should be deprived of half its value by parsimony in dyeing? The slightest shortcomings in dyeing are revealed in wear. The writer cannot forbear referring to an illustration directly before his eyes. He is wearing a garment, reduced now to the retired service of an office coat, made of an admirable cheviot cloth of American manufacture. The cloth originally was selected not only for its excellent texture, but as an illustration of philosophical principles applied in the formation of color. The tissue was made by weaving three yarns of distinct colors,—blue, yellow, and red. Either of those hues alone would have been glaring and conspicuous, but, by the law of color, the combination of blue, red, and yellow makes black, and the new cloth at a distance had the effect of a dark mixture. Upon exposure to ordinary wear, the yellow and red have retained their pristine hues; the blue, not being indigo dyed, has faded; and the original dark mixture, although sound in fabric, has become of a yellowish brown. The extra expense of a permanent dyeing material forms so small a proportion of the whole cost of a finished garment, that it ought not to be generally spared. The reform cannot be made by the manufacturers; it must be made by the dealers, and especially by that class of producers which has risen in our day into such great importance,—the manufacturers of ready-made clothing. If they would demand of the manufacturers, and furnish to their customers cloths more permanently dyed, it would be another step in the direction to which these establishments are tending,—the supply of the chief portion of the woollen clothing of the people. The manufacturers would gladly aid them; for it is the growing sentiment of American manufacturers that all their productions should be, in the proverbial phrase adopted from the dye-house, as expressing the highest excellence,—true blue.
BIBLIOGRAPHY.
Citations of authorities having been but partially made in the preceding article, the writer, for the purpose of giving his sources of information, and for the convenience of those who wish to pursue the subject further, appends a list of the more important works which he has consulted:—