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having been boiled some time, are to be transferred to the beer-wort, and with it to be again boiled.
When the hops are mixed with the wort in the copper, the liquor is made to boil, and the best practice is to keep it boiling as fast as possible, till upon taking a little of the liquor out, it is found to be full of small flakes like that of curdled soap. The boiling copper is, in common breweries, uncovered : but in many, on a large scale, it is fitted with a steam-tight cover, from the centre of which passes a pipe, that terminates by several branches in the upper, or mashing copper. The steam, therefore, produced by the boiling, instead of being wasted, is let into the cold water, and thus raises it very nearly to the temperature required for mashing, besides impregnating it very sensibly with the essential oil of the hops, in which the flavour resides.
When the liquor is boiled, it is discharged into a number of coolers, or shallow tubs, in which it remains until it becomes sufficiently cool to be submitted to fermentation. It is necessary that the process of cooling should be carried on as expeditiously as possible, particularly in hot weather, and for this reason, the coolers in the brewhouses are very shallow. Liquor made from pale malt, and which is intended for immediate drinking, need not be cooled lower than 75 or 80 degrees; of course this kind of beer may be brewed in the hottest weather, but beer brewed from brown malt, and intended to be kept, must be cooled to 65° or 70° before it is put into a state of fermentation. Hence in the spring, the month of March, and in autumn, the month of October, have been deemed the most favourable for the manufacture of the best malt liquor,
From the coolers the wort is put into the working tun, in which it is mixed with yeast, in the proportion of a gallon to four barrels of wort, in order to excite the vinous fermentation. This process is called tunning. By this the beer obtains its strength and spirit; the sugar extracted from the malt being converted into alkohol. In four or five hours the fermentation begins. Its first appearance is by a white line on the surface of the liquor, next to the side of the vessel, which gradually advances to the middle, till the whole surface is covered with a scum, or froth, formed by innumerable minute bubbles of carbonic acid gas, which rise through the liquor. The temperature of the liquor increases, and the whole is much agitated. The froth on the surface accumulates, and constitutes the yeast. At this time the presence of carbonic acid gas may
be easily perceived, by holding one's head over the barrel or tun; and fatal accidents have happened through the accumulation of this gas in situations where persons have been exposed to it without being able to remove.
The vinous fermentation must be checked in time, otherwise the acetous fermentation would begin ; all the spirit would be lost, and the beer would become sour.
The fermentation requires from 18 or 20 to 48 hours; and the beer is then put into smaller barrels, called cleansing tuns. In thein, the fermentation goes on again, and during a few days, a copious discharge of yeast takes place from the bung-hole. Care must be taken that the barrels are filled every day with fresh liquor. This discharge gradually becomes less, and in about a week it ceases; when the bung-hole is closed.
The liquor is now suffered to stand for some
time to fine (or become transparent), by depositing the mucilage that was suspended in it. When there is time, the beer is allowed to fine itself; if not, a preparation of isinglass and sour beer, called finings, is put into it, to precipitate the mucilage.
A larger quantity of hops are used in porter than for ales. Although in porter the brown malts are necessary, it is bad economy to use them too highly dried for the deepening of the colour, since the consequence of drying too highly is a carbonization of part of the saccharine matter. A dark colour may be procured more economically by adding burnt sugar to the wort.
It is in Britain prohibited by law to use any substance in brewing, as a substitute for hops.
BLEACHING. Bleaching is the art of whitening cloths, made from vegetable or animal substauces, by depriving them of their colouring matter. The art is of great antiquity; and mankind, in all ages, appear to have admired garments of a pure whiteness. The effects produced by the air and rain upon vegetable fibres exposed to them, must have led originally to the idea of producing this by artificial means. The ancients appear to have been acquainted with the uses of soap and leys; and to have practised bleaching, nearly in the same manner as it existed
among us until lately. But few manufactures have received so much benefit from modern chemistry, as that now under consideration; so that since the year 1786, it has undergone a complete change.
Bleaching of Linen. The processes of bleaching differ materially, according to the different materials of which cloths
are composed: thus, linen, cotton, woollens, and silk, are whitened by different methods. In order to understand the rationale of the bleaching processes, it is necessary to be acquainted with the nature of the materials.
Flax, from which linen is formed, is a vegetable consisting of several coats or layers. The external coat is a very thin bark; under this is a green juice or sap; next lies a layer of fibres or filaments, which constitutes the part used for making linen ; and, lastly, in the centre, there is a woody part. To prepare flax for making cloth, the filaments or fibrous part must be separated from the rest. The filaments are held together by the sap, or succulent part. To detach them from this, the flax is steeped for several days in pools or ponds of soft stagnant water; by which the putrefactive fermentation takes place. But this fermentation must not be suffered to proceed too far; otherwise the fibres themselves would be affected by it, and their texture injured. The flax must be taken out while it is yet green, and while the wood breaks easily between the fingers. The putrefaction of the sap occasions the water in which the flax is steeped to be extremely offensive; and it is even found that the fish are destroyed in any stream where this process is used.
In some places, instead of steeping the flax in water, it is simply exposed to the dew by laying it on the grass.
The time required for this part of the process is variable; depending upon the state of ripeness of the flax, the quality and temperature of the water, and other circumstances.
After steeping the flax, where the watering system is practised, it is spread very thin on the grass,
and occasionally turned, until it is found to be very brittle; so that on being rubbed between the hands, the woody part easily separates. It is then dried by the heat of the sun or of a kiln.
The flax is now ready to be beat or broke by a mill for the purpose, or by mallets on a sort of wooden anvil. The fibres of the flax are thus separated from the wood, which is reduced to fragments, most of which are cleared away by scutching. : To divide completely the fibres from each other, and to separate the remaining part of the wood, the process of hackling is employed. This consists in drawing the flax through piles or groups of sharp and polished iron spikes, placed close together, and fixed in wood. The hackles are of various degrees of fineness ; that is, the spikes are placed at different degrees of distance from each other. The coarsest, or most open hackles, are used first; then a finer, and so on, till the process is completed. · The flax is now ready to be spun into thread or yarn, which is manufactured into cloth by the weaver.
The linen, as it comes from the loom, is of a brownish grey colour; and it is then that the process of bleaching begins.
The linen is first steeped in cold water for 48 hours, to discharge from it the weaver's dressing; which is a paste of flour and water, that had been brushed into the yarn to enable them to stretch it more easily.
The grey substance that colours the linen before it is bleached is of a resinous nature, and consequently it is insoluble in water. It is also intimately united with the fibres of the flax, and is of difficult separation. What appears to the eye to be a single fibre is, in fact, a bundle of minute filaments, agglu.