

1>VI 





Such dye* w are ca|*Ue of ; '-g from the soluble into the in- 

 oluble state, and of tliiu *iT^nh permanent, without the addition 

 of a mordant, have been ailed MibstAiiUvr, and all the others have 

 beta called adjective colour*. Indigo and tannin are perhaps the 

 only dyes of organic origin to which the title substantive can be ap- 

 plied, and eren they probably are eo altered by atmospheric oxygen, 

 in th.-ir fixation upon stub, a< to form no exception to t! 

 theory of mordanU. 



Mordant* are of primary importance in dyeing; they enable us to 

 rary the colour! alimwt indefinitely with the nine dye, to increoae 

 their lustre, and to give them a durability which they otherwise 

 could not possess. A mordant is not always a simple agent ; but in 

 the mixture of which it consisU various compounds may be formed, 

 so that the substances may not act directly, but through a series of 

 transformation*. The China blue process [CALICO PHIXTISCJ] affords 

 a fine illustration of this truth. Sometimes the mordant is mixed 

 with the colouring matters ; sometimes it is applied by itself first of 

 all to the stuff; and at others both these methods are conjoined. 

 We may dye successively with liquors containing different substances, 

 which will act differently according to the different mordants succes- 

 sively employed. One solution will give up its base to the stuff only 

 when aided by heat ; another acts better and more uniformly when 

 cold, though this is a rarer caw. 



When a mordant consists of a changeable metallic oxide, as of iron 

 nr tin, unless great nicety be used in its application, either no effect 

 or an injurious one may be produced upon the dye. All these circum- 

 stances prove how necessary it is for the dyer to be thoroughly versed 

 in chemical science. Each of the great dye-works in Alsace, cele- 

 brated for the beauty and fixity of their colours, is superintended in 

 the laboratory department by a gentleman who has studied chemistry 

 for two or more sessions in the universities of Paris or some other 

 eminent schools. The English cotton dyers, twenty or thirty years 

 ago, were far inferior in skill to those of France ; but they have 

 recently made great advances. Now many of the Manchester houses 

 have chemists (some of them men of great attainments), and no doubt 

 in other towns also; and for smaller establishments there are pro- 

 fessional consulting chemists. 



The first principle of dyeing fast colours, we have seen, consist* in 

 causing the colouring matter to undergo such a change, when deposited 

 upon the wool or other stuffs, as to become insoluble in the liquor of 

 the dye-bath. The more powerfully it resists the notion of other 

 external agents, the more solid or durable is the dye. Generally 

 peaking, a piece of well-dyed cloth should not be materially affected 

 by hot water, by soap and water, by exposure to air and light, by 

 dilute nitric acid, or even by very dilute aqueous chlorine. 



In the following details concerning the art of dyeing we shall con- 

 sider principally its application to wool and silk, having already 

 treated, in the article CALICO PRIXTISU, of what is peculiar to cotton 

 and linen. 



The operations to which wool and silk are subjected preparatory to 

 being dyed are intended, 1 , to separate certain foreign matters from 

 the animal fibre ; 2, to render it more apt to unite with such colouring 

 particles as the dyer wishes to fix upon it, as also to take therefrom a 

 more lively and agreeable tint, as well as to be less liable to soil in 

 use. The matters foreign to the fibre are either such as are naturally 

 associated with it during its production by the animal, such as have 

 been added to it in the spinning and weaving operations, or such as 

 have been accidentally applied. 



Silk is scoured by means of boiling in soap and water, whereby it is freed 

 from a varnish, improperly called gum. This consists of an azotised 

 compound, which may be separated in a gelatinous form by cooling the 

 hot water saturated with it. It constitutes about a fourth part of the 

 weight of most raw silks, and contains a little colouring matter of an 

 orange or yellow hue. When silk is required to be extremely white, 

 cither to be woven in that state, or to receive the brightest and purest 

 dyes, it should be exposed to the action of humid sulphurous acid. For 

 dark dyes, silk need not be scoured at all, in which case it preserves 

 it* whole weight. Wool is first washed in running water to separate 

 its coarser impurities ; it is then deprived of its yolk (a species of 

 t.iml soap secreted from the skin of the sheep) either by the action of 

 ammoniacal urine, by soap and water, or by a weak lye of carbonate 

 of soda. Common wools lose in this way from 20 to 50 per cent. 

 of their weight, and merino wools still more. They receive their 

 final bleaching by the fumes of burning sulphur, or by aqueous 

 sulphurous acid. 



Wools present remarkable differences in their aptitude of combining 

 with dye-stufls, depending upon the different structure of the im- 

 brications of the filaments. The colouring particles seem to insinuate 

 themselves at these pores with greater or less facility, and to be 

 retained with greater or less force, according to the magnitude and 

 form of the orifices. This difference in dyeing, therefore, is not due 

 to the repulsive action of fatty matter, as bis been commonly supposed, 

 since it still exists in wool even when every particle of grease has been 

 removed from it by alcohol and ether. A boiling in a solution of 

 bran is often had recourse to, in order to make wool take the dye more 

 readily and equally ; but a hot lye containing one-half per cent, of 

 crystallised carbonate of soda answers much better. When heated to 

 the temperature of 140 or 160* Fahr., the wool Hhould be immersed 



in that liquor, and turned about fur half an hour. The wool receives 



: -li tint in. m this bath, but it speedily becomes wl 

 exposure to air ; or it may be whitened at once by pasting it through 

 tepi.l water containing a Tary small quantity of muriatic acid. The 

 yellow colour in most probably occasioned by the reaction of the 

 sulphur and iron contained in the wool. 



According to the experiment* of Tbenard and Hoard, alum combines 

 with wool in the state of a salt, without separation of it- 

 turnt. Wool boiled with a solution of tartar decomposes a pors 

 it oattxtMtj; some of the acid and a little of the tartar cm. 

 with the wool, while a neutral tartrate of potash remains in tli. 

 This fact is interesting in reference to the scarlet dye, r 

 important part which tartaric acid here performs. 



Tinctorial colours are either simple or rni|><> nul. The him pie are 

 black, brown or dun, blue, yellow, and red ; the compoun i 

 purple, green, orange; and other numerous modifications, nil 

 ducible by the mixture of simple colours. We shall treat I 

 Uatt and brown , in the present place. 



1. }{lafi.lt we apply to a white stuff blue, red, and yellow, in . 

 proportions, the resulting colour will be black. Proceeding on tlii- 

 principle, Castel asserted that 15 parts of blue, . r , 

 yellow, will produce a perfect black ; but in making this stat 

 he was influenced rather by theoretical than practir 

 In fact he has afforded us no means of procuring these simple > 

 in an absolute state. It is undoubtedly true, howevei 

 and blue, employed in adequate quantities, will produce black : because 

 they will together absorb, or obstruct the passage of all coloured 

 or, in other words, cause its total privation, whence blackness must 

 result. If we suppose a piece of cloth, to which these three 

 have been communicated, but not in such proportions as to produce a 

 pure black, we shall have a tint corresponding to the coloi 

 i* in excess ; as, for example, a blue, violet, red, or gm 

 and with paler tints we shall have a bluish, violet, red, or gr. 

 gray. 



Oall-nuts, and a salt of iron, so generally employed for the bla< I 

 give merely a violet or greenish-gray, and never a pure 

 pyrolignite of iron, which contains a brown empyreuiiiatic matter, pro- 

 duces a brown inclining to greenish-yellow in light shades, and to 

 chestnut-brown in dark hues. By galling cotton and silk, after a bath 

 of pyroUgnite of iron, and repeating the processes several tunes, a 

 tolerably pure black may be procured. (Jails, logwood, ami .1 

 iron (copperas) produce merely a very deep violet-blue ; but if they be 

 applied to wool in a hot bath, with freijuent exposure to air, the log- 

 wood induces a brownness which is favourable to the formal 

 black. 



The black dye for hats is communicated by logwood, copperas, and 

 verdigris mixed in certain proportions in the same bath ; from that 

 mixture there results a vast quantity of an ochreous muddy pi 

 tate, amounting to 25 per cent, of the copperas employed. 1'his mn.I 

 forms a deposit upon the hats which not only corrodes the fine beaver 

 filaments, but causes both them and the felt to turn speedily of a runty 

 brown. A well-dyed black hat should retain its original tint as long as 

 it lasts, a condition seldom realised. Beaver hate, however, to w liii-li 

 these remarks refer, have been almost superseded by those c. 

 with silk plush, to which a different process of dyeing applies. 



Since gall-nuts give a blue precipitate with the peroxide salts of iron, 

 they are occasionally replaced by sumach, bablah, &c. ; but account 

 should be taken in this substitution of the proportions of red or y< How- 

 colouring matter in these substances, relatively to the tannin which 

 alone forms the blue precipitate. When a black of the best possible 

 shade is to be given, the wool should be first grounded with indigo, 

 then passed through a bath of logwood, sumach, and protosulphate of 

 iron (green copperas). Sumach and nut-galls may also be empl 

 the proportion of 6 to 2J ; or the sumach may be replaced by nut-galls, 

 if they be equal to one-third of the sumach prescribed. A good black 

 may be dyed upon an indigo ground with lOOlbs. of wool, by taking 

 200 Ibs. of logwood, 60 IDS. of sumach, 2J Ibs. of galls, nn<! L'< 

 green copperas ; and giving three heats of two hours each to th> 

 with airings between. A good black, without an indigo blue ground, 

 may be given to 100 Ibs. of wool, by boiling it in a bath of 25 Ibs. of 

 alum and 674 of tartar; grounding it with weld and mad. l.-i : tlu-n 

 passing it through a bath of 200 Ibs. of logwood, 60 of sumach, and ijj 

 of galls; taking it out, adding to the bath 20 Ibs. of copperas; lastly, 

 giving it three heats of two hours each time. 



The best French black, according to Hellot, may be given to w. 

 first dyeing it a dark blue in the indigo vat ; then washing and fulling 

 it; then, for every 50 Ibs., putting into t!,, ooppcr glba, 

 galls, and as much logwood tied up in a coarse canvas bag, ami I oiling 

 them for twelve hours. One-third of the batli ired is to be 



transferred into another copper with 1 11>. of verdigris, and tli 

 or stuff is to be worked in this solution without intermission for two 

 hours : the bath being kept hot, but not tailing. After taking out 

 the stuff, another third part of the first bath is to be added .il.m^ with 

 4 Ibs. of green copperas; the fire must be lowered while this salt U 

 being dissolved, and the bath being refreshed with a little cold 

 the stuff is to bo worked through it for half an hour, and then aired. 

 Lastly, the residuary third of the first bath is to be now introduced, 

 taking care to squeeze the contents of the bag. From 8 to 101b. of. 



