Influence of Light.—Guyot says that the direct light of the sun causes wine to work, especially red wine, and that it has an injurious effect upon its composition and color; and the coloring matter being decomposed, or modified, acts upon the other elements and makes the wine turn. And hence the wisdom of putting wine in colored bottles. It is only the direct light of the sun, however, that is to be avoided, for a dim light, light reflected or polarized, and moonlight and artificial light are not sufficiently powerful to produce a sensible effect.
Aging by Sunlight.—Exposure to the rays of the sun has been resorted to for the purpose of aging wine, but Boireau says that it is not favorable to all, and is least suited to those whose alcoholic strength does not exceed 15 per cent. He says that the direct rays of the sun falling upon bottled wines will promptly precipitate the coloring matter, and that the effect is greater where the bottles are not completely filled and corked with the needle. If the bottles are wrapped in paper, or if the wine is in casks, the aging is less rapid. He shows by experiment that insolation is advantageous only to wines of more than 15 per cent. of alcohol, to sweet wines, and wines fortified up to 18°, intended to be treated as the wines of Madeira, i. e., baked. But wines of about 10 per cent. of spirit will not endure this method of aging without more or less deterioration by souring.
Effect of the Motion of Voyages.—Wines age more rapidly if kept in motion, and hence, in part, the good effect of a long voyage. Strong, sweet wines, are undoubtedly greatly improved by the motion consequent on transportation, as well as by the heat, but constant agitation will cause weak ones to go rapidly through the periods of their existence, and degenerate.
Wines Suitable for Shipment.—And Dr. Guyot adds that a wine which does not contain 12 per cent. of alcohol and 6 per cent. of sugar, crosses the equator with great difficulty, even in bottles. In wood it should be young and contain 20 per cent. of spirit, or sufficient sugar to make up that amount. For a voyage in Europe, or to America direct, he says that the wines of Bordeaux, Burgundy, and of Champagne, of 10 to 12 per cent. of spirit and 2 to 4 per cent. of sugar, behave well if young or in bottles.
Mr. Boireau, however, says that wines proper for exportation, and which will keep in tropical climates, where good cellars and good care are generally wanting, are those which possess naturally or by addition a high alcoholic title, a solid, but bright and handsome color, a clean taste, and perfect limpidity. Sweet, fortified wines best fulfil these conditions. He says that liqueur wines, for shipping to the tropics, should have at least 18 per cent. of pure alcohol; below that they ferment, their saccharine matter is transformed into alcohol, their strength diminishes, and they end by becoming pricked. Dry wines, to be sent to those countries, should have the same strength, unless the casks are kept full. He adds, however, that these remarks only apply to those wines which on their arrival do not receive the usual care, such as filling the casks, clarifying and racking, and are not kept in suitable places; and that a good firm wine of the south of France, which has naturally at least 12 per cent. of alcohol, can be shipped without fortifying.
The motion and the high temperature to which wines are subjected in transportation also cause a loss of color by precipitation, particularly if they lack tannin. Wines which are sufficiently strong in alcohol, but from lack of tannin want firmness and body, are liable to acidify. Therefore, wines too poor in tannin should not be shipped abroad. The greater part of the wines of the Gironde having plenty of tannin, can be safely shipped if fortified to 11 per cent., and the grand wines of less alcohol are safe if shipped in bottles.
In Shipping a New Wine, whose sensible fermentation is finished, the motion often causes a new disengagement of carbonic acid, and sometimes in sufficient force to burst out a head of the cask, unless vented. Of course, such wine should not be shipped, except under conditions which admit of careful supervision. If transported short distances, a small gimlet hole should be kept open near the bung, in which three or four straws may be placed with the heads or spikes on, or a small tin tube with a button at the top may be placed in the hole and bent inside the stave, having sufficient play to allow the gas to escape. Must is shipped in the same way.
Other Motion, such as Jarring and Trembling, produced by loud noises and bypassing teams and by factories, act injuriously upon wines, causing them to behave badly and to deteriorate. Guyot also says what may be by some deemed fanciful, that musical sounds hasten the development of wine; and that most old wines will turn in a cellar transformed into a music hall.
Fining is also resorted to for the purpose of aging wine, producing results somewhat similar to the effects of time. But it should be performed with the care and subject to the conditions mentioned in the proper place. (See [Fining].)
Aging Generally.—Before subjecting a wine to any of the processes for artificial aging, care should be taken, says Mr. Boireau, to precipitate the matters held in suspension, and to render it perfectly limpid.