Filtering Cane Juice. 35 



FILTERING CANE JUICE. 



Some of the impurities with which cane juice, as it comes from the mill, is loaded, 

 exist in a state of solution. In this condition they are absolutely inseparable from the 

 fluid. But, there are other foreign matters, consisting of fragments of cane, clusters 

 of minute juice cells, washings from the stalks, etc., which are mechanically sus- 

 pended in the juice, and which may be removed by filtration. A portion of these 

 substances will in time settle to the bottom, and others will rise to the surface ; but, by 

 far the largest part remain for a long time floating in the juice, giving it a dense 

 turpid appearance. The particles are too small to indicate themselves separately to 

 the eye, and by an ordinary process of filtering they either pass through without being 

 arrested, or, if obstructed, the filtering substance soon becomes clogged and matted, 

 stopping the passage of the juice. It is extremely desirable to remove as much as 

 possible of these insoluble matters from the juice before it goes to the pan. Some of 

 them, if allowed to remain until the juice boils, impart an offensive taste and color to 

 the syrup ; other portions are dissolved by heat and remain permanently in the juice, 

 and others operate to destroy the cohesion of the .scum, so that in place of coming of! 

 in well matted consistent masses, it becomes disintegrated or broken up into fragments, 

 which again mingle with the juice, and do not afterward appear on the surface. We 

 feel confident the importance of filtering the juice well, as a first step in the operation, 

 is not sufficiently regarded. By filtering we do not mean simply passing the juioe 

 through a coarse sieve or riddle, or the ordinary plan of passing it through a tub or 

 box filled with straw. The juice at first percolates freely through, in small, swift 

 currents, leaving only the larger masses of matter on the top of the straw, or entangled 

 in its meshes, while the fine particles are all carried down by the current. Gradually 

 the smaller interstices in the straw become filled or clogged, and the juice finds its way 

 only through the large openings. Soon these become stopped and the filter begins to 

 overflow, carrying over into the tank much of the coarse trash which has been depos- 

 ited on the top of the straw. Presently the operator discovers what is going on and 

 plunges his hand into the filler and raises and loosens thestraw, so that the juice 

 again flows through freely. By this means he succeeds in liberating most of the sub- 

 stance which has been previously separated and allows it to be washed through into 

 the tub. After awhile another overflow and another washing down is performed, and 

 so on through the day. The operation is obviously absurd ; and, as much as we favor 

 filtering, we cannot allow that this is much better than running the juice direct from 

 the mill to the pans. We will describe a simple apparatus in which they are prac- 

 tically embodied. It consists of an oblong box, say for two or four horse mill, six 

 feet long and fifteen inches square on the inside. 'Fill it with clean, bright straw, well 

 crowded in. Bore two holes in or near one end, qne near the top and the other near 

 the bottom of the box. Insert a hollow plug in the upper one and a hollow plug with 

 a spigot in the lower one. This completes the apparatus. Allow the juice to run 

 from the mill into one end of the box and let it fill until it flows out through the upper 

 hollow plug at the other end of the box. By this ineans the juice percolates through 

 the straw for six feet, and in an area the cross section, of which is fifteen inches square. 

 The result is, the current in the box is so slow as to be almost imperceptible ; the sus- 

 pended matter is left adhering to the straw all through the space, and nowhere does it 

 collect and form an impervious mat. The whole success of this apparatus depends 

 upon keeping the box full of juice, and. drawing from the upper plug in place of the 

 one near the bottom. If the juice is taken from the lower plug the apparatus becomes 

 like any other filter; the juice runs through in swift currents, the straw presently 

 becomes clogged, and the operation, so far as filtering is concerned, may as well be 

 abandoned. 



Once a day the juice contained in the box may be drawn off, very slowly, through 

 the lower plug, and the straw passed through the mill,' to express the suspended juice, 

 and the box defined out and filled with fresh straw. In cool, clear weather this will 

 not be required daily, but it should not be deferred more than two days. The juice 

 comes off remarkably clear and transparent and the results of the filtering are apparent 

 in the appearance of the scum, and more than all in the ultimate quality of the syrup. 



Another cheap and efficient filter is made by having a box about 30 inches deep, 

 30 to 40 inches square at the top, and tapering to 20 to 30 inches at the bottom. About 

 four inches from the bottom a false bottom is placed, perforated with holes, and upon 

 this coarse gravel, covered by layers of increasing fineness in succession to the top, 

 which is clean, fine sand. The juice is adrhitted into the open space below, under a 

 slight pressure, and, filtering upward through the gravel and sand, escapes by a pipe 

 above. 



