The plant required in the manufacture of olive-oil on a moderate scale consists of a mill for crushing, a press for separating the oil from the solid portions of the fruit, receivers into which the oil is run from the press, and the necessary vessels for storage and for the market. Besides these, there must be a building of some kind in which the various operations are carried on. In the large majority of cases, the machinery employed is of the rudest kind, and its merits rest entirely upon its simplicity. The mill is universally an edge-runner, made of some perfectly non-absorbent material, such ss granite or red marble. The motive power may be cattle or water. The press is usually of the old screw or beam types, such as any carpenter conld construct. In Spain, the oil is stored in immense stoneware jars, called tinajas. Fig. 1020 shows the complete arrangement of a mill and refinery, for extracting all the available oil, suited to the needs of a planter. The most improved apparatus for conducting operations on a very extensive Beale is described in separate sections of the present article (see pp. 1451, 1459).
The wooden or leaden pipe a with a tap at b, is for admitting water into c, which is a stone or wooden tank of sound and solid construction, with a millstone on the floor perforated in the middle. The hard-wood beam d, generally of oak, is held vertical by a cross-beam, and penetrates the wall of c, into the opening i; a horizontal water-wheel 1 is here attached to it, and it rotates on its axis at k. The millstone g is generally 5-6 in. thick, and 4-5 ft. deep ; the heavier it is, the better the crushing is performed. The wheel 1 is driven by the current of water supplied by the channel nz. The feed of this water is important, as it determines the speed at which the apparatus is driven ; the motion must net be too rapid, or there would be a danger of re-absorption of part of the oil. The channel n is for the escape of the crushed fragments and liberated oil from the tank c ; it is made in a zigzag, to relieve the rush of the water and materials into the reservoir p. To prevent the inflow from stirring up the sediment on the bottom of the reservoir, it is made to impinge on a slab of wood fixed close to the end of the spout n. The 1st reservoir p is made of either stone or brick ; it is the largest of the series, and commonly measures 10 ft. by 8 ft. The outlet from p is made by a valve q, connected with a spout r, the exit being from the centre of the depth of the tank, and not from the surface. The spout r empties into the 2nd tank s, impinging on a slab as in the 1st. The tank s communicates directly with t, and t with x, the exits being at the centre, as
shown at y. The water that flows from the upper part of the tank c is charged with remnants of the fruits, a little oil, and some particles detached from the kernel of the fruit, known as "black crust " ; the other parts of the kernel remain at the bottom of the tank, but as they retain little bits of fruit, provision is made for their withdrawal by a hole in the wall of c, connected with a pipe f, which thus carries the water and the rest of the fruit, called "white crust," into a tank h, communicating with two others j u by valves similar to q. The mode of operation is as follows. The husks of the olives, after having been crushed in the ordinary mill, are spread on the floor of the refining-mill, to be taken from there into c. When there is a sufficient quantity in a, the mill is set in motion for hour, so that the crust (husk) is crushed another time. After this, b is opened to let in some water, and the wheel is made to turn again. The force of the water rushing rapidly, and that of the mill, serve to more completely dissolve the husks ; more water is added to turn the wheel, and at last all the water is let loose. The black crust rises to the surface, and the water flowing through n drags it into the tanks p, s, t, x. When it appears that the water drags no more particles of black crust, the valve at the bottom is opened, and then the water carries off the white crust into the tanks h, j, u. When the waters of these black and white crusts have arrived into their respective tanks, or when the vat is emptied of whatever kind of crust, the vat is re plenished with husks.
While this operation is going on again, a man near the tanks, armed with a long-handled scraper or rake, passes it lightly over the surface of the water in the tank, and thrusts it into the corners, so that the oil and particles of the fruit come to the top, upon which he takes a short handled perforated ladle, or what is still better, a hair sieve, and gathers all that is ou the surface to throw it into a bucket. He goes on with this work till the water of the different tanks, without being agitated, shows nothing more on its surface ; hereupon he carries his bucket over to the boiler e, into which he empties the contents. This boiler is half full of water, which is allowed to boil until the smoke is quite white and thick, which is a sign that the water has evaporated sufficiently, and that the paste is thick enough.