Straining and Filtering. The operations of straining and filtering are frequently required in domestic manipulations, and the apparatus employed usually consists of sieves and a jelly-bag. As in many other instances, it will be found advantageous to import several contrivances from the laboratory to the kitchen. One of the most useful (because most simple) strainers consists of a square frame, formed of four pieces of wood nailed together at the corners, with a piece of calico. linen, or canvas, of suitable fineness, tacked to the four sides. This strainer is particularly useful in separating any solid substance - as the residue in making wines; or if grated potatoes are put on one made of coarse cloth, the starch can be readily washed through, leaving the useless portion on the strainer; the cloth should not be tacked very loosely, as it bags down when any substance is put on it, and the liquid runs away below from the centre. This strainer is a most useful one ; it is readily made, of any degree of fineness, and of any size ; and it also possesses the great advantage, that, if necessary, the tacks fastening the cloth can easily be withdrawn, when the substance remaining can be rolled up in the cloth, and tightly squeezed, to express the last portions quid, which are frequently the most valuable.
In cases where a finer filtration is required than can be obtained by means of a cloth, as in cleaning turbid wine or spirit, the use of filtering-paper is recommended. This paper is merely a stouter kind of blotting-paper. thick varieties of which answer very well for domestic purposes; it is most simply used by taking a square piece, folding it into half - by bringing the two opposite edges to gether - and then folding the oblong so obtained across its length. By this means a small square is obtained, one quarter the original size, which may be opened into a hollow cup, having three thicknesses of paper on one side, and one on the other; this is to be placed, with the point downwards, in a funnel, and the liquid poured in; and as soon as the pores of the paper are expanded by the moisture, it will be found to low through perfectly clear. Care must be taken, in making the filter, not to linger it much where, the two foldings cross each other, as a hole is readily made at that part, and the filter spoiled. The objection to this simple contrivance is, that from its flat sides applying themselves closely to those of the funnel, the flow of the liquid is impeded, and is therefore slow. This effect may be obviated by the use of the plaited filter, the construction of which we will endeavour to describe. A square piece of tillering or stout blotting-paper, is to be doubled, and the oblong so obtained is to be again folded in half, when, if the last fold is opened, it will have the appearance of fig. 6. From the corners, b b, folds are to be creased in the direction towards a, but not reaching it for half-an-inch ; these are indicated by the dotted lines, which divide the double paper into four triangles, each of which is to be again folded into eights; and care must be taken that all the folds are made the same way, that is. projecting to the same side of the paper. "When complete, the doubled and creased paper will appear as fig. 7. Now divide each eighth into half, by a fold in the opposite direction to those previously made, when it will be found that the whole will readily fold up like a paper fan. The projecting loose ends which are formed by the corners b, should be cut off, and the double sides separated for the first time by blowing them apart, when the whole may be readily opened out as in fir. 8.
In making this filter, which takes a much less time than to follow the description, two precaution! are requisite. The folds should be made at once with one firm pressure, and not with a series of rubbings ; and all the creases should stop short of the middle, otherwise a hole will be made at that point long before the filter is completed. The advantages of this filter are, that it exposes a large surface for the liquid to pass through; and from its only being in contact with the funnel where the angles project, the current flows always readily. - From InquiRe Within.