Bucking or Bowking

—This is one of the most important operations in the bleaching of both cotton and linen goods. There are several methods whereby this proce is carried on; but of these we shall select only two, distinguishing them as the old and new method of bucking. In the former way, the cloths have been steeped in the alkaline lye, as before described, and afterwards well washed, are regularly arranged in a large wooden vat, or kieve; a boiler of sufficient capacity is then filled with caustic alkaline lye, which is heated to the temperature of blood. The boiler is then emptied by a stop-cock 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 stop-cock, 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 elevated to a higher temperature, and the lye 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 lye is completely saturated with the colouring matter taken from the cloth, which is known by its having acquired a completely offensive smell, and losing its causticity. When we consider the effect which heated liquids have upon coloured vegetable matter, we shall see the propriety of the temperature of the alkaline lye being gradually increased. Thus, when vegetable substances are hastily plunged into boiling liquids, the colouring matter, in place of being extracted, is, by this higher temperature, fixed into them. It is on this principle that a cook acts in the culinary art, when the green colour of vegetables is intended to be preserved: 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, the green colour would be entirely extracted, whereas, when the vegetables are not infused until the water is boiling, the colour is completely preserved or fixed. On the same principle, when the temperature of the alkaline lye is gradually raised, the extractive and colouring matter is more effectually taken from the cloth; and the case is reversed when the lye 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 lye is saturated with colouring matter, it is run off as unfit for further use in this operation; but, were the goods to be instantly taken out of the kieve, and carried to be washed in the dash-wheel while hot, a certain portion of the colouring 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 as soon as the impure lye is run off: this combines with and carries off part of the remaining impurities. A stream of water is then allowed to run upon the cloth in the kieve, until it comes off almost transparent. The goods are now to be taken to the wash-stocks, or to the dash-wheel, to be further cleaned, with the greatest efficacy. The improved mode of bowking was the invention of Mr. John Laurie, a native of Glasgow. It is now practised by many bleachers in Lancashire, some on more perfect plans than others; but we shall give the description of the kind of apparatus approved of by those whose experience and skill have rendered them the most competent judges. IMG:4147767755307473660_illo0138a.png:Wooden kieve In fig. 122. , A B C D is the wooden kieve, or kier, containing the cloth; C E F D represents the cast-iron boiler; G G , the pump; g K , the pipe of communication between the kieve and the boiler. This pipe has a valve on each of its extremities: that on the upper extremity, when shut, prevents the lye from running into the boiler, and is regulated by the attendant by means of the rod and handle g B . The valve at K admits the lye; but, opening inwards, it prevents the steam from escaping through the pipe g K . The boiler has a steam-tight iron cover, g L ; and at C D , in the kieve, is a wooden grating, a small distance above the cover of the boiler. At M O is a broad plate of metal, in order to spread the lye over the cloth. It is hardly nece ary to say that the boiler has a furnace, as usual, for similar purposes. While the lye is at a low temperature, the pump is worked by the mill or steam-engine. When it is sufficiently heated, the elasticity of the steam forces it up through the valves of the pump, in which case it is disjoined from the moving power. N P is a copper spout, which is removed at the time of taking the cloth out of the kieve. IMG:4147767755307473660_illo0138b.png:Bleaching boiler The boilers A , fig. 123. , used in bleaching, are of the common form, having a stopcock, H G , at bottom, for running off the waste lye. They are commonly made of cast iron, and are capable of containing from 300 to 600 gallons of water, according to the extent of the busine done. In order that the capacity of the boilers may be enlarged, they are formed so as to admit of a crib of wood, strongly hooped, or, what is preferable, of cast iron, to be fixed to the upper rim or edge of it. To keep the goods from the bottom, where the heat acts most forcibly, a strong iron ring, covered with netting made of stout rope, C , is allowed to rest six or eight inches above the bottom of the boiler. Four double ropes are attached to the ring E , for withdrawing the goods when sufficiently boiled, which have each an eye for admitting hooks from the running tackle of a crane. Where more boilers than one are employed, the crane is so placed, that, in the range of its sweep, it may withdraw the goods from any of them. For this purpose, the crane turns on pivots at top and bottom; and the goods are raised or lowered at pleasure, with double pulleys and sheaves, by means of a cylinder moved by cast-iron wheels. The lid is secured by the screw bolts D D , and rings B B . F is a safety valve. The efficacy of Laurie’s bowking apparatus is remarkable. While the heat is gradually rising, a current of fresh lye is constantly presented to the different surfaces for saturating the goods, so as to increase its detersive powers. Besides, the manner in which the apparatus is worked, first by the water-wheel or steam-engine, and then by its intrinsic operation, puts it completely out of the power of servants to slight the work; not to speak of the great saving of alkali, which, in many cases, has been found to amount to 25 per cent. IMG:4147767755307473660_illo0139a.png:Bowking apparatus IMG:4147767755307473660_illo0139b.png:Bowking apparatus A simple modification of the bowking apparatus is shown in figs. 124 , 125 , 126. ; the first being a vertical section, the second, a horizontal section in the line x of the first. It consists of two parts: the upper wide part, a a , serves for the reception of the goods, and the lower or pot, b , for holding the lye; c c is an iron grating, shown apart in fig. 126. The grating has numerous square apertures in the middle of the disc, to which the rising pipe d is screwed fast. The upper cylinder is formed of cast iron, or of sheet iron well rivetted at the edges; or sometimes of wood, this being secured at its under edge into a groove in the top edge of the lye-pot. The mouth of the cylinder is constructed usually of sheet iron. e e is the fire-grate, whose upper surface is shown in fig. 125. : it is made of cast iron, in three pieces. The flame is parted at f , and pa es through the two apertures g g , into the flues h h , so as to play round the pot, as is visible in fig. 125. ; and escapes by two outlets into the chimney. The apertures i i serve for occasionally cleaning out the flues h h , and are, at other times, shut with an iron plate. In the partition f , which separates the two openings g g , and the flues h h , running round the pot, there is a circular space at the point marked with k , fig. 125. , in which the large pipe for discharging the waste lye is lodged. The upper large cylinder should be encased in wood, with an intermediate space filled with sawdust, to confine the heat. The action of this apparatus is exactly the same as of that already explained. Besides the boiling, bucking, and other apparatus above described, the machinery and utensils used in bleaching are various, according to the busine done by the bleacher. When linen or heavy cotton cloths are whitened, and the busine is carried on to a considerable extent, the machines are both complicated and expensive. They consist chiefly of a water-wheel, sufficiently powerful for giving motion to the wash-stocks, dash-wheels, squeezers, ., with any other operations where power is required. IMG:4147767755307473660_illo0140a.png:Wash-stocks Figs. 127 , 128. represent a pair of wash-stocks. A A are called the stocks, or feet. They are suspended on iron pivots at B , and receive their motion from wipers on the revolving-shaft C . The cloth is laid in at D , and, by the alternate strokes of the feet, and the curved form of the turn head E , the cloth is washed and gradually turned. At the same time, an abundant stream of water rushes on the cloth throughout holes in the upper part of the turn head. Wash-stocks are much used in Scotland and in Ireland. In the latter country, they are often made with double feet, suspended above and below two turn heads, and wrought with cranks instead of wipers. Wash-stocks, properly constructed, make from 24 to 30 strokes per minute. This mode of washing is now entirely given up in Lancashire, where a preference is given to what are called dash-wheels and squeezers. The dash are small water-wheels, the inside of which is divided into four compartments, and closed up, leaving only a hole in each compartment for putting in the cloth. There are, besides, smaller openings for the free admi ion and egre of the water employed in cleansing. The cloth, by the motion of the wheel, is raised up in one part of the revolution of the wheel; while, by its own weight, it falls in another. This kind of motion is very effectual in washing the cloth, while, at the same time, it does not injure its strength. The plan, however, where economy of water is of any importance, is very objectionable; because the wheel must move at by far too great a velocity to act to advantage as a water-wheel. IMG:4147767755307473660_illo0140b.png:Wash or dash-wheel The wash or dash-wheel, now driven by power in all good bleach and print-works, is represented in fig. 129. , upon the left side in a back view, and upon the right side in a front view (the sketch being halved). Fig. 130. is a ground plan.