Most of the bottles used for Champagne come from the factories of Loivre (which supplies the largest quantity), Folembray, Vauxrot, and Quiquengrogne, and they cost on the average from 28 to 33 francs the hundred.[411] They are generally tested by a practised hand, who, by knocking them sharply together, professes to be able to tell, from the sound that they give, the substance of the glass and its temper, though occasionally a special machine, subjecting them to hydraulic pressure, is had recourse to.
The operation of washing, which takes place immediately preceding the bottling of the wine, is invariably performed by women, who at the larger establishments accomplish it with the aid of machines, provided at times with a revolving brush, although small glass beads are generally used by preference. Each bottle after being washed is minutely examined, to make certain of its perfect purity, and is then placed neck downwards in a tall basket to drain.
[Illustration: MACHINE FOR FIXING THE AGRAFES.]
With the different Champagne houses the mode of bottling the wine, which may take place any time between April and August, varies in some measure, still the _tirage_, as this operation is called, is ordinarily effected as follows: The wine, after a preliminary test as to its fitness for bottling, is emptied from the casks into vats or tuns of varying capacity in the _salle du tirage_. From these it flows through pipes into oblong reservoirs, each provided with a row of syphon-taps, on to which the bottles are slipped, and from which the wine ceases to flow directly the bottles become filled. Men or lads remove the full bottles, replacing them by empty ones, while other hands convey them to the corkers, whose guillotine machines are incessantly in motion. Speed in the process is of much importance, as during a single day the wine may undergo a notable change. From the corkers the bottles are passed on to the _agrafeurs_, who secure the corks by means of an iron clip termed an agrafe; and they are afterwards conveyed either to a spacious room above-ground known as a cellier or to a cool vault underground, according to the number of atmospheres which the wine may indicate.
With reference to these atmospheres, it should be explained that air compressed to half its volume acquires twice its ordinary force, and to a quarter of its volume quadruple this force--hence the phrase of two, four, or more atmospheres. The exact degree of pressure is readily ascertained by means of a manometer, an instrument resembling a pressure-gauge, with a hollow screw at the base, which is driven through the cork of the bottle. A pressure of 5-3/4 atmospheres constitutes what is styled a 'grand mousseux,' and the wine exhibiting it may be safely conveyed to the coolest subterranean depths, for no doubt need be entertained as to its future effervescent properties. Should the pressure, however, scarcely exceed four atmospheres, it is advisable to keep the wine in a cellier above-ground, that it may more rapidly acquire the requisite sparkling qualities. If fewer than four atmospheres are indicated, it would be necessary to pour the wine back into the casks again, and add a certain amount of cane-sugar to it; but such an eventuality very rarely happens, thanks to the scientific formulas and apparatus, which enable the degree of pressure the wine will show to be determined beforehand to a nicety. Still mistakes are sometimes made, and there are instances where charcoal fires have had to be lighted in the cellars to encourage the latent effervescence to develop itself.[412]