DYEING. 



257 



Processes 

 of Dyeing. 



Conjecture! 

 concerning 

 the use of 

 dung and 

 ether animal 

 matters. 



Effects of 



'he aluin. 



sings without benefiting the dye. It appears to us, 

 that a great part of the oil employed, uniting itself (as 

 it must do) with the caustic soda, can operate merely as 

 a detergent, and that it is only the excess which com- 

 bines with the stuff, and affords a ground for the co- 

 louring matter. In the process followed at Astracan, 

 the oil is applied immediately to the cotton, without 

 the intervention of an alkali ; and at Masulipatam and 

 Pulicat, where the reds are excellent, the cotton is soak- 

 ed either in the oil of sesamum, or in melted hogs-lard; 

 and being afterwards pressed, to free it from the super- 

 fluous oleaginous matter, it is exposed to the sun and 

 air for some days : this operation is repeated three times, 

 after which the cotton is well washed. We may con- 

 clude, from these facts, that the union of the soda with 

 the oil is not absolutely essential to the impregnation of 

 the stuff with the latter ; and that the object in view 

 may be attained by the direct application of a suitable 

 quantity of oleaginous matter, the cotton having been 

 previously well scoured and prepared for its reception. 

 306. We are not prepared to speak so decidedly witli 

 regard to the effects that may be produced by the dung, 

 or the blood of ruminating nnimals ; though Chaptal, 

 Le Pileur d'Apligny, and Felix, have all given it as 

 their opinion, that whatever effect these substances may 

 have in heightening the vivacity of the colour, they do 

 not at all contribute to its durability. Dr Bancroft has 

 expressed his sentiments on this subject more cautiously 

 and philosophically : After a great numl>er of unsuccess- 

 ful attempts, which he varied in every possible way, to 

 produce the colour in question from oil, galls, and 

 alum, he has concluded, " that the gelatine contained 

 in the dung of ruminating animals, or the, albumen 

 which it also affords in a much larger proportion, or 

 some other matter derived from it, and probably from 

 their blood, is essentially necessary to produce that fix- 

 ity, as well as beauty of colour, for which the Turkey 

 red is so much admired ; though at present We only 

 know with certainty of this matter, and this colour, 

 that both may be communicated by the successive ap- 

 plications and operations which have been recently de- 

 scribed, but of the particular effect of either we are in 

 a great degree ignorant." See Philosophy of Permanent 

 Colours, vol. ii. p. 273. 



307. The process of galling is attended with several 

 advantages : The acid contained in the decoction of galls 

 decomposes the saponaceous liquor with which the cot- 

 ton is impregnated, and thus tends to fix the oil in the 

 stuff, while the astringent principle unites with the 

 oil, and forms a compound which is little soluble in wa- 

 ter, and has a considerable affinity with the colouring 

 principle of madder. The oil may also owe much of 

 its fixity to it> being mixed with the gelatinous matter 

 derived from the dung, and the mixture being after- 

 wards precipitated and attached to the cloth by the tan- 

 nin of the galls. In confirmation of this opinion, it may 

 be stated, that, by the common process of dyeing mad- 

 der, red, the addition of a little glue is found to add 

 greatly to the Ix-.-uity of the colour. In short, were we 

 to advance any theoretical opinion on a subject which 

 is -till involve 1 ! in so much uncertainty, we would ven- 

 ture to offer as a conjecture, that the ultimate effect of 

 the different steps of the process for dyeing Turkey 

 red, previous to the aluming step, is impregnating the 

 fil>re> of the cotton with a small portion of a leathery 

 oleaginous matter. 



The other ingredient which enters into the 

 composition of the mordant for this celebrated colour, 



VOL. VIII. PART I. 



is alum, which in this case operates in die usual manner, Processes 

 by heightening the madder-red, and giving fixity to the fty' >; "'g- 

 colouring matter. If the impregnation, which we have ""Y"^ 

 supposed, actually takes place, it will be easy to explain 

 the increased affinity of the stuff for the aluminous mor- 

 dant, as well as the superior brilliancy which the latter 

 communicates to the colouring matter. The stuff, par- 

 taking of the nature of animal substances, by reason of 

 the operations to which it has been subjected, must 

 possess similar properties with respect to colouring mat- 

 ters, and absorb the dye with corresponding lustre and 

 effect. 



309. The mordant composed of these different sub- Remarks of 

 stances, is undoubtedly the most complicated of any Chaptal on 

 which is employed in dyeing ; and it still deserves to "j Tur * e >' 

 be investigated with attention. " It is only from a rc ' 

 great degree of precision/' says Chaptal, " in this com- 

 bination, and a great portion of judgment in the artist 

 who produces it, that a beautiful colonr can be expect- 

 ed ; but though it be possible for him t conduct him- 

 self without error, through the labyrinth of these nu- 

 merous operations, by taking the clue of experiment 

 as his guide, he will find it very difficult to simplify his 

 progress, or bring it much nearer to perfection. It is only 

 by reasoning on his operations, and calculating the re- 

 sult, as well as the principle of each, that he can hope 

 to become master of his processes, to correct their faults, 

 and to obtain invariable products. Without this, the 

 practice of the most experienced artist will afford no- 

 thing in his hands, but the discouraging alternative of 

 success and disappointment." 



CHAP. III. 



Processes for Dyeing Yellow. 



810. A yellow colouring matter, possessing different 

 degrees of brightness, is afforded by a great variety of matters pi- 

 substances ; but under all its modifications, it has a du ^' in g>" cl - 

 very slight affinity for -tuffs, and must be fixed by the 

 intervention of mordants. The substances from which 

 yellows are usually extracted, are weld, rhus cotinus 

 or fustic, sumach, annotta, dyer's broom, turmeric, and 

 quercitron : of these, the most important are weld and 

 quercitron. 



I. Processes for Dyeing Wool Yellow. 



311. The yellow communicated to wool by weld, has reparation 

 little durability, unless the stuff be previously impreg- ' t *' c stu "' 

 nated with some mordant. Alum and tartar are ac- 

 cordingly employed, and by their means wool acquires 



from that plant a beautiful and permanent yellow. 



312. For the boiling, which is managed in the usual Weld bath. 

 way, Hellot directs four ounces of alum to every pound 



of wool, and only one ounce of tartar ; though many 

 dyers use them in equal quantities. In preparing the 

 weld bath, the plant is inclosed in a bag of thin linen, 

 and prevented from rising in the boiler, by means of a 

 heavy wooden cross. .Some boil it till it sinks to the 

 bottom, and keep it there by a cross, while others take 

 it out with a rake, and throw it away. 



313. Hellot recommends five or six pounds of weld Procemof 

 for every pound of cloth ; but the quantity must be pro- Hdlot. 

 portional to the depth of shade required. Lighter and 

 brighter shades may be obtained by dyeing after deep- 

 er ones, water being added at each dipping, and the 



bath kept boiling ; but light shades procured in thi 

 2 K 



