701 



DYEING. 



DYEING. 



70 1 



which it originates. Now, if seed be carefully obtained from a variety 

 rather more dwarf than usual, some of the plants produced by that 

 seed will be somewhat more dwarf than their parents. The most 

 dwarfed individuals again selected for seed will originate a race yet 

 more dwarf than themselves; and thus, with patience and by suc- 

 cessive generations, a variety only a few inches high may be obtained 

 from a species two or three feet high, or even higher. This is the 

 origin of dwarf roses, dahlias, ami other common cultivated flowers. 



With the exception of this la-st-mentioned method, all the others, 

 however different they may seem, proceed from the same principle ; 

 for whether we graft upon stocks whose tissue differs in organisation 

 from the scion, or whether we bend the branches, or cut or confine 

 the roots, we prevent the full flow of the sap in all such cases, 

 and thus advance the age of puberty and bring on a fruit-bearing 

 state. When plants have arrived at this stage of existence, all 

 their energies are directed to the formation of fruit ; hence forcing a 

 tree into an early state of fruit bearing is almost synonymous with 

 dwarfing it. 



DYEING is the art of staining textile substances with permanent 

 colours. To cover their surfaces with colouring matters removable by 

 daily use would be to apply a pigment rather than to communicate a 

 dye. Dye-stuffs can penetrate the minute pores of vegetable and 

 animal fibres only when presented to them in a state of solution, and 

 they can constitute fast colours only by passing afterwards into the 

 state of insoluble compounds with the fibres themselves. Dyeing thus 

 appears to be altogether a chemical process, and to require for its due 

 explanation and practice an acquaintance with the properties of the 

 elementary bodies, and the laws which regulate their combinations. 

 It is true, nevertheless, that many operations of this, as of other 

 chemical; arts, have been practised from the most ancient times, long 

 before any just views were entertained of the nature of the changes 

 that took place. Mankind, equally in the rudest and most refined 

 state, have always sought to gratify the love of distinction by staining 

 their dress, sometimes even their skin, with gaudy colours. Moses 

 speaks of raiment dyed blue, and purple, and scarlet, and of sheep- 

 skins dyed red, circumstances which indicate no small degree of 

 tinctorial skill. He enjoins purple stuffs for the works of the taber- 

 nacle and the vestments of the high priest. 



In the article CALICO PRINTING we have shown from Pliny that the 

 ancient Egyptians cultivated that art with some degree of scientific 

 precision : seeing that they knew the use of mordants, or of those sub- 

 stances which, though they may impart no colour themselves, yet 

 enable white cloth to absorb colouring drugs. Tyre, however, was 

 the nation of antiquity which made dyeing its chief occupation and the 

 staple of its commerce. There is little doubt that purple, the sacred 

 symbol of royal and sacerdotal dignity, was a colour discovered in that 

 city, and that the discovery and use of the dye contributed to tfi*e opu- 

 lence and grandeur of the place. Homer marks the value as well as 

 antiquity of this dye, by describing his heroes as arrayed in purple 

 robes. Purple habits are mentioned among the presents made to 

 Gideon by the Israelites from the spoils of the kings of Midian. The 

 juice employed for communicating this dye was obtained from two 

 different kinds of shell-fish, described by Pliny under the names of 

 pvrpura and buccinum ; and was extracted from a small vessel, or 

 sac, in their throats, to the amount of only one drop from each animal. 

 A darker and inferior colour was also procured by crushing the whole 

 substance of the buccinum. A certain quantity of the juice collected 

 from a vast number of shells being treated with sea-salt, was allowed 

 to ripen for three days ; after which it was diluted with five times its 

 bulk of water, kept at a moderate heat for aix days more, occasionally 

 skimmed to separate the animal membranes, and when thus clarified 

 was applied directly as a dye to white wool, previously prepared for 

 this purpose by the action of lime-water, or of a species of lichen called 

 fuciiH. Two operations were requisite to communicate the finest 

 Tyrian purple : the first consisted in plunging the wool into the juice 

 ill tlio purptira ; the second, into that of the buccinum. Fifty drachms 

 of wool required one hundred of the former liquor, and two hundred of 

 the latter. Sometimes a preliminary tint was given with coccus, the 

 kermes of the present day, and the cloth received merely a finish from 

 the precious animal juice. The colours, though probably not nearly so 

 brilliant as those producible by our cochineal, seem to have been very 

 durable, for Plutarch says, in his ' Life of Alexander" (chap. 36), that 

 the Greeks found in the treasury of the King of Persia a large quantity 

 of purple cloth, which was as beautiful as at first, though it was 190 

 years old. The difficulty of collecting the purple juice, and the 

 tedious complication of the dyeing process, made the purple wool of 

 Tyre so expensive at Rome that in the time of Augustus a pound of it 

 cost nearly SO/, of our money. Notwithstanding this enormous price, 

 such was the wealth accumulated in that capital, that many of its 

 leading citizens decorated themselves in purple attire, .till the em- 

 peror* arrogated to themselves the privilege of wearing purple, and 

 |.rhibited it use to every other person. This prohibition so much 

 i raged the art of dyeing purple as eventually to occasion its 

 extinction, first in the western and then in the eastern empire, where, 

 however, it existed in certain imperial manufactories till the llth 

 century. 



Dyeing wan little cultivated in ancient Greece. The people of Athens 

 wore, generally, woollen dreaeei of the natural colour. But the Romans 



must have bestowed some pains upon this art. In the games of the 

 circus, parties were distinguished by colours. Four of these are 

 described by Pliny, the green, the orange, the gray, and the white. 

 The following ingredients were used by their dyers : a crude native 

 alum mixed with copperas, copperas itself, blue vitriol, alkanet, lichen 

 rocellus or archil, broom, madder, woad, nut-galls, the seeds of pome- 

 granate, and of an Egyptian acacia. 



The moderns hare obtained from the New World several dye-drugs 

 unknown to the ancients, such as cochineal, quercitron, Brazil wood, 

 logwood, annatto, &c. ; and they have discovered the art of using indigo 

 as a dye, which the Romans knew only as a pigment. But the vast 

 superiority of our dyes over those of former times must be ascribed 

 principally to the employment of pure alum and solution of tin as mor- 

 dants, either alone or mixed with other bases ; substances which give to 

 our common dye-stuffs remarkable depth, durability, and lustre. Another 

 improvement in dyeing of more recent date is the -application to textile 

 substances of metallic compounds, such as Prussian blue, chrome yellow, 

 manganese brown, &c. 



Indigo, the innoxious and beautiful product of an interesting tribe 

 of tropical plants, which is adapted to form the most useful and sub- 

 stantial of all dyes, was actually denounced as a dangerous drug, and 

 forbidden to be used, by our parliament in the reign of Queen Elizabeth. 

 An Act was passed authorising searchers to burn both it and logwood 

 in every dye-house where they could be found. This Act remained in 

 full force till the time of Charles II. ; that is, for a great part of a 

 century. The purpose of this statute was professedly to check the use 

 of two dye-drugs supposed to be dangerous ; but it is probable that 

 the legislation was suggested by the growers or makers of certain 

 English drugs, to favour their monopoly. 



Mr. Delaval made many ingenious experiments to prove that the 

 particles of dye-stuffs possess no power of reflecting light, and that, 

 therefore, when viewed upon a dark ground, they all appear black, 

 whatever colour they may exhibit when seen by light transmitted 

 through them. He hence inferred that the difference of colour shown 

 by dyed cloths is owing to the white light which is reflected from the 

 textile fibres being decomposed in its passage through the superinduced 

 colouring particles. We think it more than probable that this con- 

 clusion is in some respects incorrect, and that the aluminous, iron, and 

 tin bases form combinations with dye-stuffs which are capable of 

 reflecting light, independent of the reflection from the fibre itself. 

 There can be no doubt, however, that this latter reflected light adds 

 greatly to the brightness of the tints, and that the whiter the textile 

 substance is, the better dye it will, generally speaking, receive. It is 

 for this reason that scouring or bleaching of the stuffs is usually 

 prescribed as a process preliminary to dyeing. 



Bergman appears to have been the first who referred to chemical 

 affinities the phenomena of dyeing. Having plunged wool and silk into 

 two separate vessels, containing solution of indigo in sulphuric acid 

 diluted with a great deal of water, he observed that the wool abstracted 

 much of the colouring matter, and took a deep blue tint, but that the 

 silk was hardly changed. He ascribed this difference to the greater 

 affinity subsisting between the particles of sulphate of indigo and 

 wool, than between these and silk ; and he showed that the affinity 

 of the wool is sufficiently energetic to render the solution colour- 

 less by attracting the whole of the indigo, while that of the silk 

 can separate only a little of it. He thence concluded that dyes owed 

 both their permanence and their depth to the intensity of that at- 

 tractive force. 



We have therefore to consider in dyeing the play of affinities 

 between the liquid medium in which the dye is dissolved and the 

 fibrous substance to be dyed. When wool is plunged in a solution 

 containing cochineal, tartar, and salt of tin, it readily assumes a beau- 

 tiful scarlet hue ; but when cotton is subjected to the same bath it 

 receives only a feeble pink tinge. Dufay took a piece of cloth woven 

 of woollen warp and cotton weft, and having exposed it to the fulling- 

 mill in order that both kinds of fibre might receive the same treatment, 

 he then subjected it to the scarlet dye ; he found that the woollen 

 threads became of a vivid red, while the cotton continued white. By 

 studying these differences of affinity, and by varying the preparations 

 and processes, with the same or different dye-stuffs, we may obtain 

 an indefinite variety of colours of variable solidity and depth of 

 shade. 



Dye-stuffs, whether of vegetable or animal origin, though susceptible 

 of solution in water, and, in this state, of penetrating the pores of 

 fibrous bodies, seldom possess alone the power of fixing their particles 

 so durably as to be capable of resisting the action of water, light, and 

 air. For this purpose they require to be aided by another class of 

 bodies, already alluded to, which bodies may not possess any colour in 

 themselves, but serve in this case merely as a bond of union between 

 the dye and the substance to be dyed. These bodies were supposed, in 

 the infancy of the art, to seize the fibres by an agency analogous to 

 that of the teeth of animals, and were hence called mordants, from the 

 Latin verb manlere, to bite. But the term derived from it has gained 

 such a footing in the language of the dyer that all writers upon his 

 art are compelled to adopt it. 



Mordants may be regarded, in general, as not only fixing but also 

 occasionally modifying the dye, by forming with the colouring particles 

 an insoluble compound, which is deposited within the textile fibres, 



