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Previous Next The best candle and soap tips online! TECHNICAL TREATISE ON SOAP AND CANDLES. THE FABRICATION OF SOAPS. 271 is continued, until all the caustic soda is bound, and a perfectly neutral soap is produced. This is ascertained, by separating a small sample of the soap-mass with a solution of culinary salt, that is by refining the soap, and then dissolving it in a little distilled water. Thereby a clear, opalescent, on no account milky solution must result; otherwise there is surely yet some uusaponified fat. After a complete saponification of the fats, the soap will become thicker and opaque, boiling with little bubbles, by continuous, not too violent boiling. The more water evaporates, the more lye collects upon the bottom, and the soap becomes hard, and shows even at this high temperature an inclination to become solid ; deep furrows are formed on the otherwise nearly smooth surface. Large and shiny bubbles appear, and the soap now boils into slabs. By taking a sample and placing it in the palm of the hand, and rubbing it until it becomes cold, it will harden into dry and glistening scales, which must show no adhesion, and may even be ground into powder. Should these characteristics be wanting, should it yet have a smeary touch, then the soap is either deficient in alkali, or the alkali used is not sufficiently caustic, or it has not yet been boiled long enough. The first case could hardly occur if the proper proportion of oil and alkali had been applied from the start, but if such is the case, we should not endeavor at once to mend this, by a fresh addition of alkali, but by continuing the boiling for a longer period of time. Thus even the carbonate of soda is bound—if its quantity is not excessively large—with the fat, and thus a neutral soap is obtained. If longer boiling proves insufficient, then carefully add some caustic lye until the object is reached. Frequent investigation of the soap, as to its solubility in distilled water, should not be omitted. Many manufacturers, especially when they think that the unpropitious result is caused by an insufficient causticity of the lye, add some lime-water. This, however, is for reasons heretofore stated most emphatically to be reproved. Although a complete saponification may thereby be reached, the lime-soap formed in this manner impairs the quality of the soap far more than the small portion of unboiled fat would. In how far, by a continued boiling, a good result may be attained, can be observed by the appearance of the sub-lye. For this purpose a portion of the soap is taken out of the kettle, placed in a saucer, the lye completely separated and cooled off, and the lye tested as to its contents of alkali. If by this test, no free or carbonated alkali, or at least but very little of it, is found, we may presume that the soap is yet wanting in it, if it does not show as yet the normal condition. A slight touch, which the sub-lye may have,does not injure the soap, since it is almost impossible to finish the boiling of soap, without any touch at all. This is quite natural too, since entirely caustic lye rarely or never is applied. At the first, the free alkali is bound ; much more difficult and slower is the combination of the fat with the carbonated alkali, so that to hasten the process more caustic lye is added. In this manner nearly all the carbonated alkali remains uncombined and passes into the sub-lye. When taken out it appears upon the tongue as being too caustic, and this touch must not be deadened by the addition of fat. The soap boiling correctly into slabs, is now kept boiling until it becomes grainy. This last operation is the real grain or clear-boiling. The soap now loses all superfluous water, and unites into a small grain-like homogeneous-curdle—while all froth vanishes, and when filled into the frames, produces the common grain—(curd) soap. But if the curdle by adding water or weak lye, is again changed into a mass of a gelatinous consistency, which, however, remains separated from the sub-lye, then the so-called ground (or filled) soaps are produced. The Grinding or Filling of the Soap, whereby the soap is again changed into the semi-liquid or gelatinous state, has for its object the purification of the soap from its yet mechanically combined dross. This is done by imparting greater liquidity to it, and by allowing it before casting it into the frames to remain for several hours in the no longer heated kettle. This grinding is performed by two different modes, but is always carried out with water or a very weak lye. 272 TECHNICAL TREATISE ON SOAP AND CANDLES. Either the lye still in the kettle from the clear boiling remains in it, and so much water is added until the soap grains become liquid—for this water may be used, as has been noted above—there will still retain in most cases a touch (this is termed "the grinding from above);" or the salt lye is drawn off" and the necessary ]ye or water with a little salt is added to perform the grinding, which is termed "the grinding from below." The adding of salt is to avoid the formation of paste. The grinding from below is only necessary when very impure materials have been worked up. The operation of grinding is undertaken over a very hot fire so that the lye is constantly thrown up, and the boiling is continued until broad slabs appear, the surface shines in a honey yellow color or turns up in rosettes, and a sample taken out of it will prove the correct quality of the soap. The fire is now extinguished, and while th,e kettle is covered with the lid the soap is allowed to settle for a few hours and is then poured into the frames. The Marbling of the Soap.—To* impart to the soap the peculiar clouding or marbling, we add to it during the preliminary process of boiling, sulphide of sodium and sulphate of iron. Thus sulphate of iron and iron-soaps are formed, which admix with the soap and impart to it, when quickly cooled oft", a greenish-black color. If allowed to cool off slowly the colored and insoluble soaps contract into smaller points and give to the soap a granite-like mottled appearance. If the cooling off is still more prolonged and the manipulation while stirring (an operation by which the soap before cooling oft" is stirred with an iron rod) is conducted with a certain regularity, we obtain a beautiful marbled soap. This isespe-ecially to be done with tallow soap, the crystallized grain of which has a great inclination to separate, and which consists essentially of stearic soda soap that at first congeals into a solid mass. If it is intended to increase the marblipg, we add, towards the end of the boiling, Frankfort-black or bole Armenian—of the former for 500 kilog. (1100 lbs.) grain soap 16§'to 33| grammes (0.57 to 1.14 oz.), and we obtain in this way a black- 273 THE FABRICATION OF SOAPS. grayish marble; and of the latter to the same quantity of soap 100 to 133J grammes (3.52 to 4.69 ozs.), and a brownish-red marbling appears. To attain a handsome marbling the operation must be performed with the purest possible sub-lye which contains at the utmost but \ per cent, of the alkali and is of about 14° B. strength, and we must not add enough weak lye or water to liquefy the grain—that is, no more than is requisite to diffuse the dyeing matter equally through the soap. Finally it must be observed that the temperature during the running out, does not vary much below or above 100° C. (212° F.). The marbling will be imperfect or does not take place at all, when the soap mass is too thin, or the temperature is too high. Therefore the adding of lye must be attended to with care, commencing with the stronger and leaving off with the weaker. The operation is ended, when the soap shows flakes of a greenish color, which float upon the lye, and when the grain becomes semi-liquid without losing its rounded form. The marbling may, however, become faulty by running the soap into the frames when too much cooled oft", as it solidifies too fast without giving the various combinations (stearic and oleicsoda soap) time to separate by crystallization of the former. Because as the stearic arid palmitic acids solidify at 69° C. (156 2° F.) and 62° C, (143°.6 F) respectively, while the oleic acid is still liquid at 15° C. (59° F.), so also the soaps of the former acids harden much sooner than the oleic acid soap. The more cooled off" the soap is when run into the frames, the sooner the moment of congealing of both soaps is found to be reached, and only an imperfect separation of the same takes place, and the coloring matters, which are especially absorbed by the elaidin soap, remain likewise divided in the entire substance. If on the other hand the temperature is too high, then the elaidic soap impregnated with coloring matter precipitates, and after the stearic acid and palmitic acid soaps have crystallized the marbling does not ensue. As marbled Marseilles (Castile) soap is now made nearly everywhere, and is no longer confined to Marseilles, we will 18 274 TECHNICAL TREATISE ON SOAP AND CANDLES. note the different proportions that obtain in various localities. The calculations are for about a ton of fats. In England are used of— Olive oil, 550 pounds, or Olive oil, 700 pounds. Palm oil, bleached, 1000 " Lard, 700 " Tallow, 350 " Cocoa-nut oil,200 " Cotton-seed oil, 350 " Tallow, 650 " 2250 2250 or, Palm-kernel oil 1500 pounds. Sesame oil 450 " Tallow oil 300 " 2250 In the United States the usual formulas are— Olive oil, 700 pounds, or Palm oil (bleached) 1000 pounds Ground-nut oil, 700 " Cotton-seed oil, 500 " Lard, 850 " Tallow, 750 " 2250 ? 2250 In Marseilles we have noticed that the proportions also vary with each manufacturer, and the olive oil is in greater quantity, though there are in addition more or less groundnut oil, poppy oil, hempseed oil, sesame oil, etc. etc. White Marseilles (Castile soap).—This truly fine soap may be considered a standard as to what a pure soap should be, and has with the mottled Castile soap given character and popularity to the soaps of France and particularly to those of Marseilles. While the mottled soap cannot be well made to retain its proper marbled appearance with an excess of water, the white soap from the difference in the manner of manipulation contains more water, though nearly all impurities have to be removed to obtain the proper whiteness. White Castile soap is now made in almost all countries, and generally with the artificial sodas, and even in Marseilles these sodas are now being used. Yet in some factories the barilla is still used as the base; this alkali, containing a ?eertain percentage of potash, gives a plastic consistency to th« soap which has added to its popularity. This effect is now usually produced by the addition of a drying oil, such 275 THE FABRICATION OF SOAPS. as hempseed, sesame, ground-nut, poppy or cotton seed oil to the amount of 15 to 25 per cent, of the olive oil. These oils, instead of being a sophistication, may be considered a benefit, as they prevent the soap, which if made with olive oil alone becomes too hard in drying, from having that undesirable property. This soap is the purest to be found in commerce, when it has been prepared and purified according to the proper rules of the art. It is very much used in industrial operations, particularly in the bleaching of raw silk. By its extreme purity and its nearly absolute neutrality, it does not alter the brilliancy and elasticity of the silk, which renders it superior to all the other kinds of soap. When prepared in all its purity, it has for its basis, with the additions above mentioned, pure olive oil, saponified by caustic lyes of artificial soft soda. These lyes are prepared in the same manner as indicated for marbled soap ; but as the presence of salt would render the soap less soluble in water, the lyes must be prepared only with soft soda free from salt and containing as little as possible of sulphuret of sodium. By this precaution too much coloration of the paste is avoided, and the operation is much more easy. In Belgium, soda ash is substituted for crude soda in the preparation of the lyes. The soap thus made is of a fine pure white color. Thus by using a colorless and a purer alkali, the refining of the soap is easier, and the amount obtained much larger than with lyes made from crude sodas. This is rational, and we have seen soaps of olive oil thus prepared, which were perfectly white and as pure as the best Marseilles soap. Independently of the purity of the alkali, the nature of the oil employed to prepare this soap exercises a remarkable influence on its consistency and whiteness. To obtain good results, the whitest and most limpid oils must be used. Experience proves that oils much colored have the property of communicating their shade to the soap. Sometimes a proportion more or less considerable of another oil is mixed with the olive oil, especially earthnut oil; this oil, being 276 Previous Next
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