B L E A C 



Bleaching. The method of bleaching linens in Ireland is simi- 

 v lar to the foregoing ; any alteration in the process de- 

 pending on the j Jgment of the bleacher in increa- 

 sing or diminishing the quantity of alkali used. But 

 it is common at most bleachfields to steep the linens 

 in the oxymuriate of potash, or lime, at an early 

 stage of the process, or after the goods have under- 

 gone the fifth or sixth operation of bucking. By 

 this means, those parts of the flax which are most 

 difficult to bleach are more easily acted upon by the 

 alkali ; and, as before noticed, souring early in weak 

 diluted sulphuric acid assists greatly in forwarding 

 the whitening of the linens. Mr Grimshaw, cajico 

 printer near Belfast, was the first who recommended 

 early souring, which has since been very generally 

 adopted. 



CHAP. IV. 



Bleaching for Calieo Printing. 



Bleaching I" bleaching linen and cotton cloth, for the pur- 

 for calico pose of being stained with different colours, in the 

 printing. process of calico printing, a pure white is not so 

 much sought for, as that the goods are what is tech- 

 nically called well rooted ; that is, that the colouring 

 matter and vegetable oil is fully extracted from them. 

 This is attained chiefly by the linens being bucked 

 and boiled in a solution of alkali, rendered moderately 

 caustic by quicklime, in order to preserve the fabric 

 of the cloth from being too much reduced. The al- 

 kaline solution must be well settled, and transparent 

 as water ; because, if the lime remains either in solu- 

 tion or suspension in the smallest proportion, it is apt 

 to be precipitated into the fabric of the cloth, and 

 destroy the purity of those parts intended to be white. 

 Linen cloth requires to be bucked and boiled from 

 ten to twelve times in the alkaline solution ; being 

 well washed and exposed on the bleachgreen be- 

 tween each operation. It is soured at the end of the 

 sixth boiling ; and again soured at the end of this 

 process, when the goods are supposed fully bleached 

 for printing. 



To ascertain whether the cloth is fit for printing, 

 a small stripe is torn from the end of one of the 

 pieces, and printed with one of the mordants used 

 in the fixing of the dye. After that the mor- 

 dant has remained a sufficient time in the cloth, it 

 is rinsed in pure water to carry off the superfluous 

 parts of the mordant, and then immersed into a 

 copper pan in cold water, which contains a little 

 madder ; the heat is gradually increased, while the 

 cloth is alternately raised and lowered by a bit of 

 stick in the decoction of madder, until the colour is 

 dyed to the shade required. At this period, if the 

 cloth is properly bleached, the place stained with 

 the mordant will alone have attracted the colouring 

 matter of the madder ; while the rest of the rag re- 

 mains white. But should the part intended for white 

 be stained a dirty light red, the cloth is not fully 

 bleached, and it must again be boiled in the solution 

 of alkali. 



Cotton cloth intended for calico printing is more 

 easily bleached than linen cloth ; five, or at most six 



H I N G. 87 



boilings in the alkaline solution, being all that is re- Bleaching, 

 quisite for making a good white. One pound of pot- ''""'" v '*' 

 ashes is fully sufficient to bleach a piece of calico of 

 21 square yards. This gives about three ounces of 

 potash to each piece for every time they are boiled. 

 Between every part of the boiling process, the cali- 

 coes are washed and exposed on the bleachgreen, the 

 same as linen cloth ; and soured, at the end of the 

 process, in the same manner. In order to ascertain 

 whether they are fully bleached for printing, the 

 same method is followed as that which is already de- 

 scribed for the trial of linen cloth. 



In bleaching both kinds for printing, it is not cus- 

 tomary to immerse them in the oxymuriatic solu- 

 tions ; except in the winter months, when a good, 

 white is not so easily obtained, by the action of the , 



sun and air. Neither are the goods watered arti- 

 ficially when spread on the bleachgreen ; but they 

 are (after being well washed) allowed to lie exposed 

 to all the vicissitudes of the season, until the common 

 routine of business calls for their return to undergo 

 farther operations. This process is commonly called 

 dry bleaching, in contradistinction to that in which 

 the goods are artificially wetted when exposed on the 

 field. 



After linen or cotton cloth is printed and dyed, 

 a certain dulness of colour attaches itself to the 

 parts intended to remain white ; arising partly from 

 the imperfection of the bleaching, but more fre- 

 quently from a part of the mordant, which has been 

 printed on the cloth, being loosened by the increa- 

 sed temperature of the water bath. This unites 

 with the decoction of madder or other colouring 

 matter used in the bath, and is precipitated on the 

 parts intended to remain a pure white. To remove 

 this partial stain in an easy manner, without long ex- 

 posure upon the bleachgreen, has long been much * 

 wanted by calico printers. 



In order to attain this, various methods have been 

 resorted to without effect, arising partly from the 

 imperfection of the substances employed. Steeping 

 printed goods after being dyed, in the oxymuriate of 

 lime, not only changes all the colours, and renders 

 them of a duller hue ; but also particles of the lime 

 attach themselves so intimately to the cloth, that it 

 acts as a discharge, and effaces the colours altogether. 

 Although a dilute solution of the oxymuriate of pot- 

 ash does not act in so severe a manner as the oxymu- 

 riate of lime, yet it operates strongly as an alterative 

 to most colours ; changing the red colour to pink, 

 and the purple and lilac are turned to bluish shades 

 of the same colour ; besides, the action of the alkali 

 scourges the whole colours, by reducing their inten- 

 sity and brilliancy. In consequence of these defects, 

 bbth these substances are unfit for producing a good 

 white on printed goods ; without at the same time 

 acting as an alterative, in completely changing the 

 shade of colour wanted. 



In searching for a substance which possesses none 

 of these pernicious qualities, we have found, that the 

 oxymuriate of magnesia in every respect answers in 

 the most complete manner, not only for clearing the 

 white gn.und of the goods, but also in preserving 

 the colours of the same shade which they were origi- 

 nally. 



