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Previous Next The best candle and soap tips online! is placed, when the knives upon the cylinder soon cut it into small pieces. A still better mode is to reduce it by means of a mill having polished iron rollers similar to the mill used for toilet soaps, Fig. 70, page 435 ; this mill breaks the membranes so thoroughly that the fats are rendered sooner and better. The kettles for rendering in small factories by an open fire are similar to Fig. 76. B is the caldron ; C, steps to facilitate the stirring, filling, etc.; the caldron is egg-shaped, heated only at the base, and to prevent burning there should always be a portion of melted fat in the bottom, for if allowed to burn, the color is so injured that it cannot be bleached. When in operation the fat requires almost constant stirring, and the heat due regulation. When the fat is melted it is strained with the sieve G, into the pan E, in which it is left to cool and harden. Steam is a great assistance in these operations, and the fats In the rendering of tallows there is much offensive gas liberated, which is often a great annoyance to the neighborhood. This evil and the remedies are treated in our section on soap materials. For remedying this trouble in a great degree, it is customary to have a hood, Fig. 77, placed over Fig. 77. \ the kettle, and which is raised or lowered at pleasure, and conducts the disagreeable vapors into the chimney. 30 466 TECHNICAL TREATISE ON SOAP AND CANDLES. For extracting the fat from the greases it is necessary to have a press. These are of various kinds ; Fig. 78 shows a )i II it rasaim Fig. 78. 467 MATERIALS FOR CANDLES. A newer invention, of greater power, is the elbow press of Messrs. Boomer & Boschert of Syracuse, N". Y. (Figs. 80 and 81). The cracklings are often heated the second time, and Fig. 81. Fig. 80. very suitable one, and Fig. 79 an iron cuUendered box with the pressed cake of cracklings. Fig. 7fl. 468 TECHNICAL TREATISE ON SOAP AND CANDLES. MATERIALS FOR CANDLES. 469 again subjected to pressure to obtain as much tallow as ia possible by this process. For rendering fat on a larger scale, the steam digesters of Wilson are much used for all descriptions of fats. (See Fig. 2, on page 87.) By this means there is but a small percentage of greaves, the fat being almost entirely extracted. For a large business we show two other presses (Figs. 82 and 83, also by Boomer & Boschert) very suitable for all the purposes described in this work where a press is used. Fig. 83. In Fig. 83 is seen the largest press, having immense power, and very useful for stearic acid, paraffine, etc. The advantage of the elbow ia that the power is graduated, by being first gentle and increasing as it is straightened. For candles the rendered tallow is usually purified, to accomplish which there are various means, and for the better qualities of candles the tallow should be white and hard; one of the simplest means to >his end is to place the rendered fat Fis. 83. in a large vessel and permit it to cool very slowly, when the stearin and palrnitin will grain .or crystallize, and collect towards the edges, while the olein of the non-liquid part will be left free in the centre, when it can be ladled off, or, what is still better, it can be pressed out with the presses 470 TECHNICAL TREATISE ON SOAP AMD CANDLES. MATERIALS FOR CANDLES. 471 already mentioned. For this purpose the centrifugal mill has been constructed (Fig. 84). It consists of a drum A with Fig. 84. a circumference of gauze wire B; and has an exterior jacket C, and the,drum is attached to a shaft D drawn by the gearing E. The granulated fat, tallow or lard, being placed in the drum, it is driven at great speed ; the centrifugal action throws the granulated fat against the wire gauze, which retains the solid particles, while the liquid escapes through the meshes into the outer jacket, and is drawn oft' by the cock F. This machine works with great rapidity ; it is about four feet in diameter, and requires about one horse power to drive it. After the liquid part of the tallow is extracted, the remaining stearin will be whiter and harder, the olein having the greatest amount of color. Other processes for whitening tallow, and which harden it at the same time, are by means of chemicals. "Watts' method of bleaching tallow is with sulphuric and nitric acids, combined with bichromate of potash and oxalic acid. These substances cause the liberation of oxygen, which whitens the fats very satisfactorily. Watson's process for purifying and whitening is b}7 means of permanganate of potash with dilute sulphuric acid. The permanganate is mixed with the melted fat, and free steam blown through it, or it is briskly stirred, when sufficient dilute sulphuric acid is poured in and the heat regulated not to exceed the boiling point of water, Previous Next
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