To clarify beer, finings, made usually from isinglass, are frequently employed. Finings are prepared by planing the isinglass, or other materials, such as sole skins or sounds of cod-fish, in a vessel, and covering it to a depth of 5 or 6 inches with vinegar, or sour old beer. When the isinglass has softened and swollen up, so as to absorb this liquor, a further supply of sour beer is added, and the mixture well stirred up, the process being repeated until the whole becomes of a uniform consistency. In some breweries this pulpy liquid is mixed with weak bright beer, and strained through a hair sieve ; whilst in other cases it is thinned with the bright beer, and then allowed to become clear by depositing the insoluble matters in settling tanks. The final gravity of the finings should be about 1.025.
In using finings, they should be first mixed with a large bulk of the beer to be clarified, and after agitation the mixture should be poured into the main body, and well stirred in. After this the beer should be allowed to stand about twenty-four hours, when the impurities will be deposited. Ure considers that the clarifying action of isinglass is due to the tannin of the hops combining with the fluid gelatine, and forming a flocculent mass which envelops the muddy particles of the beer and carries them to the bottom as it falls.
Isinglass varies considerably in value, and it is important that brewers should have a ready means of judging of its quality. The best isinglass consists almost entirely of gelatine, and does not contain more than 2 per cent. of substances insoluble in water. One method of testing isinglass consists in placing a know') quantity of it in water, boiling and weighing the insoluble matters that may be separated by straining the solution. Another test consists in steeping the isin glass in spirits of wine, in which gelatine is insoluble, and then adding a few drops of tincture of galls. If a deposit is formed, it shows the existence of impurities ; whilst if tbe liquid remains clear, there is a strong presumption that the isinglass is of good quality. A practical and simple method of testing the value of isinglass or of other materials used in the manufacture of finings consists' in dissolving a given weight of the isinglass to be tested in a fixed quantity of sour beer, and then pouring the solution into a funnel, the neck or spout of which is carefully bored out to a known diameter of about ioch. The solution is allowed to flow from the funnel into a graduated glass measure for a period of time measured by a sandglass, and the quantity of solution which has run. through in this time indicates the quality of the isinglass. The higher the quality, the thicker will be the solution, and the more slowly it will flow from the funnel.
Graham remarks on the general process of brewing, that the simplest arrangement is to carry out the fermentation through its first stages in the fermentation square or round, and afterwards to complete the secondary fermentation in settling squares. This method is less wasteful and is very efficient. But in carrying out such a process exceeding care must be taken that in the settling
square the beer should be covered with a layer of carbonic acid, or in other words the gyle must be run off into the settling square before it is become dead. Graham further remarks that a rapid pro cess is not always attended with equally excellent results, and those specially engaged in preparing store ales must bear in mind that it is quite impossible for them by any rapid driving process to produce an ale of the highest excellence in a short space of time. With proper treatment of store ales, it occasionally happens that they become sour, and in such cases it is necessary to employ materials that contain quick lime or other acid-neutralizing agent.
In bottling ales, it may be necessary for the bottler to carry on the German system of slow feed ing, and as it is illegal to employ sugar for the purpose, the brewer should be called upon to supply a few barrels of wort excessively rich in sugar, and containing but little of the malt extract. This wort ought to be very highly charged with bisulphite of lime. When the store cask is fed with a little of this wort, a small quantity of bisulphite introduced into each barrel will do good rather than harm, and there is thus the advantage of slowly feeding the store cask and not in any way running counter to the excise laws.
If beer containing yeast cells is heated to a temperature of 50° to GO° (120° to 140° F.), the yeast cells are killed. Graham proposes a process based upon this discovery of Pasteur's. The beer should be run from the store cask and corked with a paraffined cork, that is with a cork saturated with paraffin wax, by which the loss that occurs from the cork giving insufficient protection against pressure is avoided. The next process is to destroy the ferment in the ale itself, because however bright the ale may be, there are always floating on it minute yeast cells. If the ale were placed in a bottle and heated to a sufficient temperature to destroy these yeast cells, ale that did not contain sufficient carbonic aoid would be unpleasant to drink because it would not effervesce. It is necessary therefore for the bottler to charge each bottle with carbonic acid ; and this may be done by merely allowing the bottles to remain until there is produced in the ale enough carbonic acid by subsequent fermentation—a process occupying two or three weeks. When the ale has thus obtained sufficient carbonic acid, it must be heated to about 60°. But if the bottler be pressed for time, and the ale is very flat and is required for immediate export, carbonic acid may be forced into the ale by an ordinary carbonic acid apparatus, and the bottles afterwards heated. In heating Burton ale up to 60°, there is a lessening of the amount of haziness due to albuminous matter, and with Edinburgh ale there is a very distinct improvement in the brilliancy. ln the public-house and restaurant, beer is sometimes fed with molasses or is rendered sparkling by the use of carbonic acid apparatus.