Page:The Olive Its Culture in Theory and Practice.djvu/174

142 properly used, the amount of pressure required may be exactly graduated. In the first pressure, usage differs as to the employment of water. It must be clearly understood, that the olive berry contains a large amount of water from which the oil separates itself when the mixed liquid is allowed to rest after the expression, and that the employment of water is not for an adulteration, or other improper purpose, but simply to free the oil and water in the berry and ease the process of pressing. Doubtless oil extracted without the use of water is appreciably finer to an expert "olive oil taster," but it is doubtful if very much of such oil reaches the market. The usage of mills differs. The most extreme divisions of oils would be, that of the first crushing and the first pressure; that of the same pomace crushed a second time; that of the same pomace treated with cold water; that of the same pomace treated with hot water; that of this pomace ground fine, placed in an agitator and heated with water, until the stones fall to the bottom and are carried away, and the water and lighter matter passed into settling tanks, where the oil is skimmed off, while a little more is made by another pressure; this is called washed oil. This same pomace instead of being treated as above, may be treated by the bi-sulphate of carbon process at special factories, with a larger percentage of oil as a result. Finally a low grade of oil is skimmed from the water used in collecting the oil, and which is carried out of the mill and deposited in tanks called from the low quality of the oil, "the inferno." The term "Virgin oil" is used so variously, that it is difficult to define it with accuracy. It is used for the first run of oil whether made with or without water; it is also sometimes used for early oil—the first of the season; the most exact use seems to be the oil which flows either without any pressure by the weight of the pomace in the racks or the cages, or just as the pressure begins to tell. Watching the press one sees pure oil and water run out, and if this is taken from the receiver at once, the oil and water separate quickly, and the oil is exceedingly rich and fine. As the pressure goes