In 601110 cases, when the process is being conducted on a very large scale, and the vats employed are of great size, it is necessary to conduct tho pressing of the grapes upon a wide floor, surrounded by a trench or gutter, connected with a cistern, from which the oxpressed juice is run into the vats. In other places, it is customary to press the grapes between two rollers placed sufficiently far apart to avoid breaking the seeds. Every distiller, however, varies the modus operandi according to the scale upon which he is working.
Tho vats are round in shape, and may be either of oak, hooped together with iron hoops, or of masonry. The latter is preferable in the case of wines intended for distillation. In the course of a day or two, fermentation sets in, and the must undergoes the changes described on p. 195, tho resulting liquid bearing the name of wine. The room in which the process is conducted should havo a temperature of about 15°, and the fruit should be at the same degree at the time of crushing. The vats may be heated before being filled.
Iu some eases, when the grapes have been grown on moist land, or the season has been a rainy one, it happens that the must contains too small a proportion of sugar, and it is, therefore, necessary to diminish the quantity of water present by artificial evaporation ; or the excess of water may be counteracted (and this is by much the better method) by the addition of the theoretical quantity of sugar required to bring the must to the ordinary strength ; this quantity is determined by the degree of concentration of the must as shown by the sacellarometer. When ascertained, the neces sary quantity is dissolved iu a little of the must by boiling over fire, and then poured intu the vat The whole is well stirred together and then covered up.
When the process is complete, the wine is drawn off, or racked. As the quality of the wine depends in a great measure, upon the perfo mance of this at the right moment, much care must be employed to determine it. The only sure guide consists in observing, by means of the sacchare meter, the prog,ress of the conversion of sugar into alcohol, so as to note the exact moment when the whole of the sa,ccharine principle is decomposed. After racking the wine, a certain quantity is always left in tho mare, at the bottom of tbe vat. This is obtained by submitting the mare to the
action of a wine-press, of which there are many varieties. The wine expressed is harsher and more tart than that previously drawn off, and should therefore be kept separate.
Wino contains alcohol in proportions varying from 7 to 21 per cent., a large proportion of water, small quantities of undecomposed sugar, besides traces of albumen, pectin, and tannin, tartaric and malic colouring matters, essential oils, &c.
In making choice of tho wines to be distilled, the first consideration is the amount of alcohol which they contain, and then the quality of- the spirit which they will yield. Their richness in alcohol is readily determined by means of Guy Lussac's One-third of the wino is distilled off and two volumes of water are added to the remainder; the strength may then be read off by means of an elooholometer. As regards the quality of the brandy obtained, much depends upon the purity, fineness, and age of the wine employed. White wines, or those made from the juice alone of the grape, are to be preferred ; all the best varieties of " Cognac " brandy are distilled from these wines.
Another variety of spirit, called in France de mare, is prepared from the mares or refuse of the wine-press. After the grapes have been pressed, the mares contain a certain amount of sugar, if the grapes were pressed before fermentation, and of wine, if this process was carried on, as is sometimes the case, after fermentation. The mares are transferred to vats where they are covered with water and stirred up vigorously. Weighted sieves are then placed in the vats in such a manner that the mare is pressed down to the bottom, leaving a layer of clear liquor above it. Air is then excluded by covering the vat securely. After fermentation, which occupies about five days, the clear liquor is drawn off and distilled. On account of its rough, unpleasant taste and odour, the spirit so obtained is seldom used for direct consumption, but is generally added to the fermenting vats for the purpose of increasing the strength of liquors which contain a small pro portion of sugar. Employed in this way, the spirit loses its objectionable qualities, and is found to enhance the colour and strength of the wine to which it is added.