are of various sizes. One of moderate dimensions may turn out from six to eight tons, and is usually formed of four pieces of cast-iron—lower casting, say fire feet in diameter; upper, eleven. Beat is applied either by means of a furnace beneath the bottom piece, or by open steam introduced by a pipe led to a circular perforated ring at the bottom of the pan. Steam boiling being now extensively adopted, our description will apply to that method..
Coot or White Soap.-20 cwt. of tallow being put into the soap-pan, and a quantity of the prepared lye, steam is turned on, and boiling continued until the lye is thoroughly incorporated with the tallow, and becomes a pasty A few shovelfuls of common salt are now thrown in when the lye begins to separate. The partially formed soap is allowed to cool, and the salted lye, now deprived of its soda, subsides, and is drawn off from the bottom by a pipe, or removed by a pump. The operation of adding and boil ing with lye is repeated until the tallow is saturated with soda, and the lyes show as much alkali after boiling as before. The soap is now treated with weaker lye, and by more or less water brought to the consistency the maker requires. From its tendency to thicken rapidly, it is transferred to the frame at a higher temperature than the soap next described.
Pale or Yellow Soap.—When the tallow is saponified as above described, about one third of its *eight of rosin is added, and the boilings with lye repeated, until the mass is thoroughly saponified. The practiced workman being aware that perfect soap is insoluble in strong alkali, avoids the risk of imperfect particles escaping the action of the lye from being enveloped iu. perfect soap, by reducing the mass with water, and adding lye gradually until the soap again floats as a curd on the liquid. The soap is then cooled and the lye being removed as completely as possible, it is boiled with the quantity of water necessary to it to the consistency required. These later operations require much experience, and the best theoretical knowledge requires the aid of tongue and eye to carry them through with success. The soap being now fin /shed (the technical term), the copper is covered up, and the contents allowed to settle until the temperature falls to about 160° Fahrenheit. According to the quantity of water used, so is the deposit, called the nigre, greater or less. When too much water is used, the produce of soap is too small; when too little, the produce is large, but of infe rior quality, from the insufficient deposit of impurities. This nigre is employed iu mak ing second-class soap. When of proper temperature, the soap is removed, into frames,
now mostly made of east-iron, containing about 101 cwt. Cacti, where, after solidifying, which it does in three days, it is cut by wile into slabs, which are again cut transversely into bars ready for the market.
London mottled is made of kitchen fat (no rosin). The process described in the mak ing of curd soap is followed here, except that when perfect the soap is, when almost boil ing, put into wooden frames three or four times as high as the ordinary frame of 52 in., and the lye allowed to percolate through the soap to the lower part of the frame, producing the mottled appearance desired. As this soap. when subjected to any mixing operation, lost its mottle. it long enjoyed a high reputation as a genuine soap; but now that cheap imitations, having a beautifully marbled appearance, are produced from cocoa and palm nut oils, with coloring and siliceous matter, its prestige is somewhat on the wane.
The numerous patents taken out for improvements in soap-making have had for the most part more the object of cheapening, by the addition of various articles to soap in its send fluid state, than of improving the manufacture.
Sqft-N.Hip differs from hard from having potash for its base instead of soda. The repeated changes of lye described in the manufacture of hard soap are here inadmissible, for all the lye employed remains in combination with the oily materials, and is never separated. Bence open steam, as throwing in water into the mass, cannot be applied, nor can salt., so useful an agent in the former manufacture, be used, as it would tend to separate the soap from the lye, while a thorough combination is essential. The making of soft-soap requires much experience and nicety, it being so easy to overdo the supply of alkali, which cannot happen in hard-soap. A ton of materials, consisting of 1900 lbs. of fish or other oil, with 840 lbs. tallow, is put into the soap-pan with 200 gallons of American potash lye of such strength that 6,600 grains of real potash are in each. After being boiled by the beat of a furnace, and well beat down on the surface to keep in hounds the frothy mass, a stronger lye, containing about 8,700 grains of potash per gal lon, is added at short intervals, and the Zsailing carried on until the workman ascertains by taste and appearance that the snap is perfect. The tallow serves to give consistency to the soap, and also produces white specks of stearate of potash, which much enhance its appearance.