BLEACHING. 



585 



Bleaclung. main too long in this state they would absolutely rot. 



' v ' It is therefore the bleacher's care to guard against so 



serious an accidei.t. 



On buck- 

 ing. 



Sect. II. On Bucking. 



This is one of the most important operations in the 

 bleaching of linen goods. There are several methods 

 whereby this process is carried on, but of these we 

 shall only select two, distinguishing them as the old 

 and new methods of bucking. In the former way, 

 the linens having been steeped in the alkaline ley, as 

 before described, and afterwards well washed, are re- 

 gularly arranged in a large wooden vat, or kieve ; a 

 boiler of sufficient capacity is then rilled with caustic 

 alkaline ley, which is heated to the temperature of 

 blood. The boiler is then emptied by a stopcock 

 upon the linens in the kieve, until they are covered 

 with the liquor. After having remained on the 

 cloth for some time, it is run off by a stopcock at 

 the bottom of the kieve, into an iron boiler sunk in 

 the ground, from whence it is raised into the boiler 

 by a pump. The heat is now raised to a higher tem- 

 perature, and the ley again run upon the goods in the 

 kieve ; from whence it is returned into the boiler, as 

 before described : and these operations are continued, 

 always increasing the heat, until the alkaline ley is 

 completely saturated with the colouring matter taken 

 from the cloth, which is known by its having acqui- 

 red a completely offensive smell, and losing its caus- 

 ticity. 



When ye consider the effect which heated liquids 

 have upon coloured vegetable matter,"we shall see the 

 propriety of the temperature of the alkaline ley be- 

 ing gradually increased. Thus, when vegetable sub- 

 stances are hastily plunged into boiling liquids, the 

 colouring matter, in place of being extracted, is by 

 this high temperature fixed into them. It is on this 

 principle which a cook acts in the culinary art, when 

 the green colour of vegetables is intended to be pre- 

 served : in place of putting them into water when 

 cold, they are kept back until the water is boiling ; 

 because it is well known, that, in the former case, 

 Vhe green colour would be entirely extracted, where. 

 a3, when the vegetables are not infused until the wa- 

 ter is boiling, the colour is completely preserved, or 

 fixed. On the same principle, when the temperature 

 of the alkaline ley is gradually raised, the extractive 

 and colouring matter is more effectually taken from 

 the cloth ; and the case is reversed when the ley is 

 applied at the boiling temperature, so much so, that 

 linen which has been so unfortunate as to meet with 

 this treatment, can never be brought to a good 

 white. 



When the alkaline ley is saturated with colouring 

 matter, it is run off, a3 unfit for further use in this 

 operation. But were the linens to be instantly taken 

 out of the kieve, and carried to be washed in the 

 tiash-wheel while hot, a certain portion of the colour- 

 ing matter would be again fixed into them, which is 

 extremely difficult to eradicate. In order to prevent 

 this, the most approved bleachers run warm water 

 upon the cloth so soon as the impure ley is run off; 

 this combines with, and carries off part of the re- 

 maining impurities ; a stream of water is then allow- 



VOL. III. PART IV. 



ed to run on the cloth in the kieve, until it come!) off Blocking 

 almost transparent. The linens are now taken to <r~' 



the wash-stocks, or to the dash-wheel, to be further 

 cleaned, with the greatest safety. 



The process of bucking was long carried on in 

 this 'manner without any improvement, until Mr 

 John Lourie, as before narrated, introduced an appa- 

 ratus admirably calculated for conducting this opera- 

 tion on the large scale, which being in some measure 

 self operative, much labour, as well as a considerable 

 quantity of alkali, is saved. 



The boiler (Plate LVI. Fig. 2.) being filled with Plate 

 caustic alkaline ley, and the linens being > properly ar- t VI ' 

 ranged in the wooden kieve above it, the handle of '&' 

 the pump GG is set in motion by the machinery : 

 the ley now flows through the pipe N by the work- 

 ing of the pump, and falling on the broad plate of 

 metal MO, it is spread in a perpetual current on the 

 cloth, while the valve K opening inwards, admits 

 the ley to return into the boiler. Immediately on 

 the pump being set to work, a fire is put to the boil, 

 er, by which the ley being gradually heated, the 

 linens receive the benefit of the regular increase of 

 temperature, and the colouring matter from the 

 cloth- is thereby more effectually removed. When 

 the ley begins to boil, the handle of the pump is 

 detached from the machinery of the water wheel, 

 and by the ley being completely confined in the close 

 boiler, it is forced up the pump, and falls in a per- 

 petual stream through the pipe N upon the linens 

 in the kieve ABCD. 



The efficacy of this manner of conducting the 

 bucking process must be evident at first sight : while 

 the heat is gradually increased, a current of fresh ley 

 is constantly presented to different surfaces of the 

 goods for saturation, thereby rendering it more ac- 

 tive in cleansing them. Besides, the manner in which 

 the apparatus is first wrought by the water wheel, or 

 steam engine, and its self-operating power afterwards, 

 puts it completely out of the power of servants to 

 slight the work, independent of the great saving of 

 alkali, which, in most cases where it has been ap- 

 plied, amounts to from one-fourth to one-third of the 

 quantity formerly used. 



Sect. III. On Boiling. 



In the bleaching of linen cloth, bailing is only On boiling, 

 used when the goods are nearly white, with pearl 

 ashes alone, or with pearl ashes along with soap to- 

 wards the end of the whitening process : all that is 

 necessary in this operation, is to keep the goods com- 

 pletely under the liquid, so that it may act uniformly 

 upon them. In no case is the boiling carried on in a 

 violent manner, but with a gentle simmering heat. 

 The boilers are made of cast iron, of the common 

 construction, with a large stopcock at bottom, in or- 

 der to empty it of the waste ley. 



Sect. IV. Immersion in the Oxymuriale of Potash. 



According to the doctrine of modern chemists, the Immersiou 

 oxymuriatic acid, in consequence of yielding up its m tne ox y- 

 oxygen to the colouring matter of vegetables, there- murii J teoi 

 by deprives them of colour, and by this means they potS! ' 11 ' 

 4 E 



