D V E I X G. 



M 



I :r:;. 



How pre- 

 pared be- 

 fore being 



<Uolrc<L 



fropertiei 

 f toe *oru- 



of copper or vcrtligriw, acquires a blue colour, of little 

 briithinesK and durabihtv. which is chic; c nd- 



cd In MB, Tin- high price of indigo I 



late rendered this mode of dyeing M 1 ,- u r.d, 



particularly i'i I-'rance. 



141. The principal consumption of logwood is for 

 bUcks, to which it gives a lustre and velvety cast, and 

 for greys of certain shades. It is also emploved very 

 different compound colours, which it 

 would he difficult to obtain of equal beauty anil variety, 

 from colouring mutters of a more permanent nature. It 



.iientlv mixed with Brazil wood, to render colours 

 deeper, the proportion of the two woods being varied ac- 

 cording to the .shade desired. In short, no colouring 



: with which we are acquainted, is capable of af- 

 fording so great a variety of dyes, though this advantage 

 is much diminished by their want of permanency. 



143. The bark of the quercus nigra of Linnseus af- 

 fords a yellow dye, which is at present very generally 

 employed. This substance was first prepared as a dye 

 by Dr Bancroft ; he having given it the name of quer- 

 citron, by which it is now universally recognized. "The 

 bark of the quercus nigra appears," according to his 

 account, " to consist of three parts or coats. J st, The 

 epidermis, or external coat, through which the several 

 excretions of the tree are transmitted, which, in part 

 at least, adhere to its outer surface, and become almost 

 black by condensation. 2d, The middle or cellular 

 coat, in which the colouring matter principally resides. 

 3d, The interior or cortical part, consisting chiefly of 

 lamina, formed by the reunion of different vessels, 

 which become more hard and fibrous as they are placed 

 nearest to the woody part of the tree, and have there- 

 fore less room to contain the colouring matter." 



143. Before extracting the colour from the bark, the 

 epidermis, or external covering, ought to be removed, 

 by shaving. The remaining parts being then properly 

 ground by mill- stones, separate partly into a light fine 

 powder, and jwrtly into stringy filaments or fibres, 

 which last yield but about half us much colour as the 

 powder, and therefore care should be always taken to 

 employ both together, and as nearly as possible in their 

 natural proportions, otherwise the quantity of colour 

 produced may either greatly exceed or fall short of 



; s expected. The quercitron bark thus prepared 

 and proportioned, says Dr Bancroft, will generally 

 yield as much colour as eight or ten times its weight 

 of the weld plant, and about four times as much as its 

 weight of the chipped old fustic. The colouring mat- 

 ter, continues he, most nearly resembles that of the 

 weld plant, with this advantage, however, that it is 

 capable alone of producirg more cheaply all, or very 

 nearly all, the effects of every other yellow dyeing drug; 

 and, moreover, some effects which are not attainable 

 by any other means yet known. 



144. The colouring matter of quercitron readily dis- 

 solves in water, even at a blood heat. If the infusion be 

 strained and left at rest, a quantity of resinous matter 

 subsides in the form of a whitish powder, which pro- 

 duces the same effects in dyeing ;:s the part ri maining 

 in solution. The clear effusion being evaporated and 

 dried, affords an extract equal in weight to about one 

 twelfth of the bark from which it was obtained. Much 

 care, however, must be emploved in procuring this ex- 

 tract, so as to make it produce colours equal in beauty 

 to those obtained directly from the bark itself. If the 

 evaporati-.il 1-e carried on rapidly, and the heat be too 

 great, the colour is tarnished, probably, as Dr Bancroft 

 conjectures, from the absorption of oxygen, the colour 

 thua undergoing a sort of semi-combustion. On the 



other h-aid, iff .ndurtctl loo slowly, 



the colouring nutter suffers another ch 



ng. 



I !.".. The decoction of quercitron is of a yellowish 

 brown colour, which is darkened In iul bright- 



ened by at ids. A solution of alum ! 

 parates.-! s.naiijiortion of the colouring matter, whichsulu 



.1 the form of a deep vellow precipitate. The sohr- 



nf tin produce a more copious precipitate, .-ml of 

 a beautiful lively yellow colour. S'/lphate of iron 



a copious olive precipitate ; sulphate of copper, 



w of an olive cast. 



146. The weld plant, (reseda liilcofa,) seems to have 

 been employed from the remotest times as a yellow- 

 dye. Two sorts of it nre di.-tingiiished, the cultivated 

 and the wild ; the former is preferred, as it \ i 

 colouring matter. The wild species dili'ers from the 

 cultivated, in producing taller and -tnjngcr stalks. The 

 whole of the plant is used in dyeing. 



147. A strong dicoctinn of weld is of a yellow colour, 

 inclining to brown ; if it : . diluted with v 



its yellow, which is mor or less pale, has a grc. 

 tinge. The addition of an alkali deepens the colour of 

 the decoction, and after a certain time n little ash-co- 

 lourcd precipitate is thrown down, which is insoluble 

 in alkalies. The iieids in general render its colour paler, 

 and produce a little precipitate which dissolves in al- 

 kalies, and gives them a yellowish brown colour. Alum 



inns a yellowish precipitate, and the liquor retains 

 a fine lemon colour. The solutions of tin produce a 

 copious bright yellow precipitate. Sulphate of iron 

 produces a copious dark grey precipitate, ;:nd the su- 

 pernatant liquor is brownish. Sulphate of copper 



s a brownish green precipitate, and the liquors 



rve a pale green colour. 



148. To extract the colour of weld for dyeing, the 

 plant is boiled in a fresh bath, inclosing it in a bag of 

 thin linen, and keeping it from rising to the top by 

 means of a heavy wooden cross. Some dyers continue 

 the boiling till it sinks to the bottom of the copper, and 

 then let a cross down upon it ; others when it is boiled, 

 take it out with a rake, and throw it away. The de- 

 coction should be employed as soon as possible after it 

 has been prepared, as it soon suffers a decomposition, 

 which renders it use' 



149. Common salt added to the weld bath, renders 

 its colour richer and deeper ; sulphate of lime or gyp- 

 sum also deepens it. Alum renders it paler, but more 

 lively ; and tartar still paler. Sulphate of iron makes 

 it incline to brown. The shades obtained from weld 

 m v )i .: odilied, with these additions, by the proportion 

 of the weld, by the length of the operation, and by the 

 mordants employed in prcp.-Ting the stuff. The colour 

 may be modified also by p.-.-^.ng the cloth, when it is 

 taken out of the bat'i, through other dyes. 



1.10. Dr Bancroft has staled M veral objections to the 

 use of weld, compared will) quercitron, as a dye. >Vhtn 

 it is emr.loyci! in topical dyeing, the colouring matter 

 of weld is fixed by a heat very little less than that of 

 boiling water, and the parts wanted to be preserved 

 white are then so much stained, that it is difficult to 

 brighten them afterwards, particularly during the damp 

 and cloudy wtv.lher of winter. U eld also produ- 

 r bad effect in topical dyeing upon linens or 

 cottons, which have previously received m.vldcr colours : 

 the weld yi How attaching itself so closely to these co- 

 lours, as greatly to tarnish and impair^ their lustre. 

 (Quercitron is nearly, if not wholly, fre-- 

 fi at* It is obvious, however, that, in many cases, '' 

 qualities must recommend the use of weld. 



Adjective 



Wild. 



Tropcrtit* 

 of the de- 

 coct "> tt - 



It* qualitiM 

 compared 

 with t' 

 crci- 



