DYEING. 



761 



through the fabric, it will receive the particles of 

 oxide of iron, at the very instant of their transition 

 from the fluid to the solid state ; by which means a 

 perfect covering of the black, inky matter will be 

 applied in close contact with the surface of the most 

 minute fibres of the cotton. 



The name of mordant is applied to those substan- 

 ces which unite with the different stuffs, and aug- 

 ment their affinity for the various colouring matters. 

 There exists a great number of mordants; some, 

 however, are very feeble in their activity, while 

 others are attended with too much expense for com- 

 mon stuffs ; some alter the colours which they are 

 intended to combine, or modify their shades : hence 

 it results, that there are but a small number which 

 can be employed. These are alum, acetate of alu- 

 mine, muriate of tin, and nut-galls. The mordant 

 is always dissolved in water, into which the stuffs to 

 be dyed are plunged. If the mordant be universally 

 applied, over the whole piece of goods, and this be 

 afterwards immersed in the dye, it will receive a 

 tinge over all its surface ; but if it be applied only in 

 parts, the dye will strike in those parts only. The 

 former process constitutes the art of dyeing, properly 

 so called ; and the latter the art of printing woollens, 

 cottons, or linens, called calico-printing. In the art 

 of printing piece goods, the mordant is usually mixed 

 with gum or starch, and applied by means of blocks 

 or wooden engravings, in relief, or of copper plates, 

 and the colours are brought out by immersion in ves- 

 sels filled with suitable compositions. The latter 

 fluids are termed baths. 



The following are the processes adopted, when 

 alum is the mordant employed : 1 . Alum mordant 

 for silk. In water containing the sixtieth part of its 

 weight of alum, at the ordinary temperature of the 

 air, the silk is plunged, and allowed to remain for 

 twenty-four hours, when it is withdrawn, drained, 

 and washed. If the liquid is warmed, it is found 

 that the silk absorbs less of the mordant, and that, of 

 course, it combines less easily with the colouring 

 matter, besides losing, in part, its natural gloss. 2. 

 Alum mordant for wool. When it is wished to com- 

 bine wool with this mordant, after its cleansing has 

 been effected, it is plunged into a boiling solution, 

 composed of 8 or 900 parts of water, and twenty-five 

 of alum, where it is allowed to remain during two 

 hours ; when it is taken out, suffered to drain, and 

 washed. Frequently a little cream of tartar is added 

 in this process, in order to engage the excess of acid 

 in the alum, as well as the portion arising from a 

 slight decomposition of the alum by the oily matter 

 of the wool. 3. Alum mordant for cotton, hemp, and 

 flax. This operation is effected by plunging the 

 body to be imbued with this mordant into water 

 slightly warmed, and which contains one quarter of 

 its weight of alum, and leaving it for twenty-four 

 hours, at the common temperature of the air ; when 

 it is withdrawn, washed, and dried. The cotton 

 will be sufficiently imbued with the mordant, if al- 

 lowed to remain in the solution only seven or eight 

 minutes, pressing it a little, without twisting it, 

 however, on taking it out, and not immersing it in 

 the colouring bath until twelve or fifteen hours 

 after. In all alum mordants for wool, the alum of 

 commerce may be employed ; but when silk or cot- 

 ton is to be dyed, especially if the. colours are bright, 

 it is necessary to make use of the alum of Rome, or 

 of that which is equally pure ; that is to say, of alum 

 which does not contain above l-500th of its weight 

 of sulphate of iron ; otherwise there will be a great 

 quantity of oxide of iron adhering to the fabric, 

 which will affect the shade we desire to obtain. The 

 colouring matters to be transferred . to the various 

 stuffs, are either soluble or insoluble in water. 



When they are soluble in water, which is most gen- 

 erally the case, they are dissolved in it at a boiling 

 temperature ; and the material to be dyed, after hav- 

 ing been duly prepared, and impregnated with the 

 mordant, is plunged into it, where it is allowed to re-- 

 main for a certain time, and at a temperature varying 

 with the nature of the stuff. When, on the contrary, 

 the colouring matter is insoluble in water, its solution 

 is effected in some other fluid, and the article to be 

 coloured (prepared as in the former case, with the 

 exception that the application of the mordant is 

 omitted) is immersed, and the colouring matter is 

 precipitated by the addition of a third body. 



Silks are dyed at a temperature which is gradu- 

 ally increased from 86 to 175' Fahr. If the bath 

 is heated above 86, at the commencement of the 

 process, the effect of the mordant is diminished, and 

 the desired shades of colour will not be produced. 

 For the same reason, in dyeing hemp and flax, the 

 temperature should not exceed 97 Fahr. Cotton 

 and wool lens may be dyed at a boiling heat. Various 

 mechanical contrivances are made use of in immers- 

 ing the different materials to be dyed into the col- 

 ouring solution, so as to cause all their parts to be 

 equally affected at the same time. As soon as they 

 are withdrawn from the colouring bath, they are 

 washed in a large quantity of water, in order to de- 

 prive them of those particles of colouring matter that 

 are merely superficial. 



The following are the dye-stuffs used for produc- 

 ing/a^ colours : 1. Black. The cloth is impreg- 

 nated with acetate of iron (iron liquor), and dyed in 

 a bath of madder, and logwood. 2. Purple. The 

 preceding mordant, diluted with the same dyeing 

 bath. 3. Crimson. The mordant for purple, united 

 with a portion of acetate of alumine, or red mordant, 

 and the above bath. 4. Red. Acetate of alumine 

 is the mordant (see Alumine), and madder is the 

 dye-stuff. 5. Pale red, of different shades. The 

 preceding mordant, diluted with water, and a weak 

 madder bath. 6. Broiun of Pompadour. A mixed 

 mordant, containing a somewhat larger proportion of 

 the red than of the black, and the dye of madder. 

 7. Orange. The red mordant, and a bath, first of 

 madder, and then of quercitron. 8. Yellow. A strong 

 red mordant, and the quercitron bath, whose tem- 

 perature should be considerably under the boiling 

 point of water. 9. Blue. Indigo, rendered soluble 

 and greenish-yellow coloured, by potash and orpi- 

 ment. It recovers its blue colour by exposure 

 to air, and becomes firmly fixed upon the cloth. An in- 

 digo vat is also made by diffusing indigo in water, with 

 quicklime and copperas. These substances are sup- 

 posed to act by deoxidizing indigo, and, at the same 

 time, rendering it soluble. Golden dye. The cloth is 

 immersed alternately in a solution of copperas and 

 lime-water. The protoxide of iron, precipitated on 

 the fibre, soon passes, by absorption of atmospheri- 

 cal oxygen, into the golden-coloured deutoxide. 

 Buff. The preceding substances, in a more dilute 

 state. Blue vat, in which white spots are left on a 

 blue ground of cloth, is made by applying to these 

 points a paste, composed of a solution of sulphate of 

 copper and pipe-clay, and,afterthey are dried, immers- 

 ing it, stretched on frames, for a definite number of 

 minutes, in the yellowish-green vat, of 1 part of indigo, 

 2 of copperas, and 2 of lime, with water. Green. Cloth 

 dyed blue, and well washed, is imbued with the 

 acetate of alumine, dried, and subjected to the quer- 

 citron bath. In the above cases, under 9, the cloth, 

 after receiving the mordant paste, is dried, and put 

 through a mixture of cow-dung and warm water. It 

 is then put into the dyeing vat or copper. 



The foregoing colours are also produced from de- 

 coclions of the different colouring woods ; but, as 



