705 



DYEING. 



DYEING. 



706 



sumach are added ; the liquor is just made to boil, then refreshed with 

 some cold water ; after which, a pound of green copperas being dis- 

 solved in it, the stuff is again passed through it for an hour. It is 

 now taken out, aired, washed, then returned to the copper, and worked 

 in the bath for another hour. It is next washed at the river and 

 fulled. A finish is prescribed in the madder-bath. 



The ordinary proportions used by the English black dyers for 

 100 Ibs. of cloth, previously treated in the indigo vat, are about 5 Ibs. 

 of copperas, as much nut-galls bruised, and 30 Ibs. of logwood. They 

 first gall the cloth, and then pass it through the decoction of logwood 

 in which the copperas has been dissolved. A finish of weld is often 

 given after fulling ; but this is of doubtful utility, especially when a 

 little soap has been used in the fulling-mill. Vitalis prefers the pyro- 

 lignite of iron to the sulphate for the black dye, and says it produces a 

 softer and more velvety colour an opinion which some English 

 chemists dispute. 



The black dye vat, as it gets exhausted, is employed to dye grays of 

 various shades. 



Silk is dyed black in two methods, according to the market for 

 which it is made. When sold by weight, as was formerly the practice 

 at Tours, and is now with silk thread in this country, it is an object 

 with the dyer to load it with as much colouring or other matter as 

 possible. Sugar is at present much employed to falsify the weight of 

 English silk thread, as any person may discover by applying a hank of 

 it to his tongue. We have seen thread more than doubled in weight 

 by this fraudulent device. Such silk is called English black by the 

 French, who are not suffered to practise this deception. When silk is 

 sold by superficial measure, on the other hand, it becomes the dyer's 

 object to give it a black colour with as little weight of materials as 

 possible. Hence the distinction well known in the trade of heavy and 

 light silks. In this, as in many similar examples of adulteration, a 

 desire on the part of some dealers to undersell their neighbours pro- 

 bably produced the evil iu the first instance; and then the others 

 joined in the fraud for self-defence. 



The 25 per cent, of weight which silk has lost in scouring may be in 

 a great measure recovered by giving it a sufficient dose of galls. For 

 this purpose a bath is made by boiling galls equal to two-thirds or 

 three-fourths the weight of the silk for three or four hours in a suffi- 

 cient quantity of water, and then letting the decoction settle for two 

 hours. The silk must be steeped in this bath from twenty to thirty-six 

 hours, and then washed in clear water. The first galling is, however, 

 commonly given with a bath somewhat spent ; and for heavy blacks 

 generally upon unsecured silk. Several successive immersions in gall- 

 baths, and of considerable duration, are usually given to silk, with 

 intervening washings and wringings at the peg. 



The silk dyers keep up from year to year a black vat, often of very 

 complex composition. The essential constituents of the vat are sul- 

 phate of iron and gum ; but many vegetable matters, as well as filings 

 of iron, are usually added. This bath being heated short of boiling, 

 and then allowed to settle for about an hour, the silks are worked in it 

 with much manipulation, occasional wringing out, airing, and re- 

 dipping. As the copperas and gum get exhausted, the bath must be 

 replenished with these ingredients in due proportions. The addition 

 of logwood and verdigris is very useful to the black silk dye, and is now 

 generally made. A ground of walnut peels is a good and cheap prepa- 

 ration for this dye. 



2. Broum or dun colour. This dye is not so common in England 

 as on the Continent, where the colouring matter is generally produced 

 at a very cheap rate by steeping ripe walnuts with their peels in water 

 for a year or two, till the vat acquires a deep brown colour and a fetid 

 smell. This infusion affords very agreeable and permanent brown tints 

 without any mordant ; while it preserves the downy softness of the 

 wool, and requires but a simple and economical process. In dyeing 

 with this infusion, a quantity of it proportional to the shade required 

 is to be put into the copper, diluted with water, and made to boil. 

 The cloth or yarn needs merely to be moistened beforehand with tepid 

 water, to be then plunged in the bath, and turned about till sufficiently 

 dyed. Some dyers, however, give the stuff a preparatory mordant of 

 alum, and leave it to drain for twenty-four hours before subjecting it to 

 the bath of walnut-peels. 



Sumach is usually employed in this country to dye fawns, and some 

 browns ; but more beautiful browns may be given to woollen stuffs by 

 boiling them first with one-fourth their weight of alum and some tartar 

 and copperas, washing, and afterwards dyeing them in a madder bath. 

 The shade of colour depends upon the proportion which the copperas 

 bears to the alum. 



A good brown may also be obtained by mordanting every pound of 

 the stuff with two ounces of alum and one ounce of common salt in a 

 boiling bath ; and then dyeing it in a bath of logwood to which some 

 copperas has been added ; or the stuff dyed red in the madder bath 

 may be turned about in the black dye vat till the required shade 

 be produced. 



The finest browns are produced by boiling each pound of the wool 

 with two ounces of alum, dyeing it in a cochineal bath, and then trans- 

 ferring it to a bath containing a little cochineal darkened with acetate 

 of iron. Instead of cochineal, the archil or cudbear bath may be used, 

 with a little sumach or galls. This forms a cheaper but a more fugitive 

 colour. 



AKTg AKD SCI. DIT. VOL. III. 



A beautiful brown tint, on wool or silk, may be obtained by first 

 giving a pale blue shade in the indigo vat, then mordanting with alum, 

 washing and finishing in a madder bath till the proper brown be 

 brought up. The Saxon blue vat may also be used. If the stuff be 

 mordanted with alum and tartar, then boiled in a madder bath, after- 

 wards in one of weld or fustic, to which more or less copperas has been 

 added, we shall have a mordore, cinnamon, or chestnut brown. By the 

 combination of olive shades with red, bronze tints may be produced. 

 For 25 Ibs. of stuff a bath containing 4 Ibs. of fustic will suffice. Boil 

 the wood two hours, then turn the stuff iu the bath for an hour, take 

 it out, and drain. Add to the bath 4 or 6 ounces of copperas and a 

 pound of madder or sandal-wood ; then work the stuff in it till the 

 wished-for shade is attained. 



Silk may receive a ground of annatto, and then be dyed in a bath of 

 logwood or Brazil wood, whereby a fine brown tint is obtained. 

 Catechu is used for giving a bronze and brown to cotton goods. 

 [CALICO-PRINTING.] Blue colours are dyed with indigo, Prussian blue, 

 and woad ; yellows with fustic, Persian berries, quercitron, turmeric, 

 and weld ; reds with archil or cudbear, Brazil wood, cochineal, kermes, 

 lac, logwood, madder, safflower, or carthamus. The purple, green, and 

 orange dyes are produced by various applications of cochineal, indigo, 

 quercitron bark, &c. 



M. Hoard, long the skilful director of the Gobelins' dye-works, has 

 observed that copper boilers exercise a considerable influence upon 

 delicate dyes. He found that ammonia causes a blue precipitate in the 

 alum bath made in such boilers ; while it causes merely a white pre- 

 cipitate in the same bath made in vessels of glass, porcelain, and tin. 

 When wool is kept for some hours in boiling water contained in a 

 copper vessel, it acquires a greenish-gray tint, a result increased by 

 the ordinary mixture of alum and tartar. If into this bath white wool 

 be plunged, it receives a greenish-yellow, or sometimes an ochrey hue. 

 These observations of M. Hoard are of considerable importance, and 

 should lead dyers to employ tin or at least brass boilers instead of 

 copper ones for all vivid colours. Heating with steam, either by double 

 vessels, by straight or spiral tubes, ought on all occasions to be pre- 

 ferred in the dye-house to naked fires, which seldom fail to carbonise 

 some portions of the vegetable or animal matters, and thereby to 

 degrade the colours. The top edge or surface of the boilers should 

 be about 3J feet above the floor ; this being a height which the work- 

 men find most convenient for their manipulations when they stand 

 upon a step 8 or 10 inches high. 



The stuffs mordanted with alum should not be transferred to the 

 bath immediately, but be allowed to drain and air for twenty-four 

 hours. The colours are thereby rendered more lively than when dyed 

 soon after the aluming. As experience has proved that an old alum 

 bath is better than one fresh made, it should not be thrown away, but 

 be strengthened or refreshed by the requisite additions of alum and 

 tartar. It is certain that wools boiled in alum the second time, are 

 more beautiful than those boiled in it the first time. 



The methods of dyeing black and brown sufficiently explain the 

 general principles, and we therefore conclude with a few observations 

 of a general nature. 



Mr. Solly, in communications recently made to the Society of Arts, 

 has drawn attention to several matters having an important relation to 

 the improvement of the art of dyeing. We will merely advert to two 

 of these subjects, the desirability of studying the chemistry of agri- 

 culture in relation to the growth of dye-plants ; and the saving of 

 freight in importing only the essential parts of dye-drugs, instead of 

 the whole bulk. 



Mr. Solly, in relation to the first of these two subjects, the influence 

 of soil and culture on the chemistry of dye-plants, said, " It was ob- 

 served that some of the madder grown near Avignon was inferior in 

 the richness and brilliancy of its colour to that produced in other dis- 

 tricts. The proprietor being anxious to discover the cause, was led to 

 institute a chemical examination of the soil of his own land, in com- 

 parison with that of some of the best madder farms. The result 

 showed that his soil was deficient in lime, while all the others con- 

 tained it. He was therefore induced to give his land a good dressing 

 of lime ; and the result fully justified this course, for in the next year 

 the crop of madder was inferior to none." 



The same authority, in relation to the bulkiness of dye-materials, 

 said, " Dye-stuffs are for the most part bulky and heavy substances, 

 the carriage of which for any distance, by land or even by water, makes 

 a very serious addition to their cost ; consequently every mode of 

 increasing the proportion per cent, of colouring matter is worthy of 

 consideration ; and those modes of preparation are best which yield 

 the largest quantity of colour, and the least quantity of useless fibrous 

 matter. Owing to the judicious manner in which the Chinese safflower 

 is collected, it contains far more of the fine red colouring matter, and 

 is consequently worth four or five times as much in the market as the 

 best Bengal safflower ; in addition to which, for want of due care in 

 the drying, the latter is sometimes so much injured during the sea 

 voyage as to be deteriorated fifty per cent. The loss thus sustained is 

 often set down to the nature of the drug, and not to the careless habits 

 of those employed in collecting it. When we remember how many 

 thousand tons of dye-woods are annually imported, and how many 

 thousand tons of it are absolutely useless woody fibre, we cannot help 

 coming to the conclusion that here chemical science might be applied 



