FIG. 57.—KNUCKLE TYPE OLEO OIL PRESS.
Press Room and Pressing Stock.
—The room into which the seeding trucks with their contents are run should be held at a temperature of 75° to 90° F. The material in the seeding trucks, which is now called “stock” should be pressed at a temperature of from 78° to 84° F., according to its quality, as well as to the percentage of stearine which it is desirable to make. The lower the temperature at which the oil is pressed the more stearine will be retained in the cloths. After the stock is chilled to above temperature it will be found that a granulation has taken effect and oil will be observed on the top, whereas the heavier and granulated parts of the fat will be at the bottom. This should be thoroughly mixed up before it is sent to the press, either by use of a dipper or mechanically, care being used not to disturb the bottom of the cooler. If there is any moisture in the bottom of the truck it would spoil the stock by mixing it. Whereas, if it is not agitated, when the stock is removed, the bottom can be examined, and, if it is good, it can be used; otherwise it should be sent to the tallow tanks. After the stock is thoroughly broken up or mixed it is ready for the press, it first being wrapped in cloths.
The cloth used in connection with this press is a medium weight piece of cotton canvas, which is cut in the proper sized pieces, about eighteen inches square. The cloth is first put on the “former” which is filled with a dipper full of stock; the attendant wraps it up carefully and the man filling the press as it comes around in the wheel, takes the wrapped stock and lays it on the plate, using eight bags of stock on each plate in the press, generally using sixty steel plates for each press. When the press is full the power is turned on. The slow speed should be used almost exclusively after the press is started in order to give the oil sufficient time to strain through the canvass.
FIG. 58.—OLEO OIL RECEIVER.
Collecting Oil.
—The oil from the press should run to a receiving tank, as many being used as is necessary to keep the different grades of oil separated. Where oil is being made in large quantities it is always advisable to have the receiving tank hold sixty tierces, or a car load of oil, for if smaller receivers are used the oil is likely to be irregular.
The quality of oil varies, as does the quality of cattle; for instance, choice native cattle, which are very fat, make a finer, better oil than western cattle which are not in as good condition, and as the killing is always liable to run irregular, if the oil is not assembled in large quantities, it is often perceptible, and a manufacturer soon acquires the reputation of making irregular oil. When that reputation is once established buyers scrutinize closely before making purchases.