850 SOAP 



pour it into the soap through the rose of a watering-pot ; boil the whole for about 

 half an hour, or an hour, and cleanse it in the ordinary -wooden frames or in iron 

 frames surrounded by matting, or other covering, so that the soap may not cool 

 too rapidly ; the above proportions will yield 212 cwts. of soap, with a beautiful blue 

 mottle. 



Manufacture of Yellow or Resin Soap. We have already said that resin, though 

 not capable of forming a soap with soda, readily dissolves in that alkali, either in the 

 caustic or in the carbonated state, with which it forms a kind of soapy mass of a 

 viscid or treacly nature ; hence fat of some 'kind, in considerable proportion must be 

 used along with the resin, the minimum being equal parts ; and then the soap is far 

 from being good. As alkaline matter cannot be neutralised by resin, it preserves its 

 peculiar acrimony in a soap poor in fat, and is ready to act too powerfully upon 

 woollen and all other animal fibres to which it is appbied. It is said that rancid tallow 

 serves to mask the strong odour of resin in soap more than any oil or other species 

 of fat. From what wo have just said, it is obviously needless to make the resin used 

 for yellow soaps pass through all the stages of the saponifying process ; nor would 

 this indeed be proper, as a portion of the resin would be carried away, and wasted 

 with the spent lyes. The best mode of proceeding, therefore, is first of all to make 

 the hard soap in the usual manner, and at the last service or charge of lye, namely, 

 when this ceases to bo absorbed, and preserves in the boiling-pan its entire causticity, 

 to add the proportion of resin intended for the soap. In order to facilitate the 

 solution of the resin in the soap, it should be reduced to coarse powder, and well incor- 

 porated by stirring with the rake. The proportion of resin is usually from one-third 

 to one-fourth the weight of the tallow. The boil must be kept up for some time 

 with an excess of caustic lye ; and when the paste is found, on cooling a sample of it 

 to acquire a solid consistency, and when diffused in a little water, not to leave a 

 resinous varnish on the skin, we may consider the soap to be finished. The maker 

 next proceeds to draw off the superfluous lyes, and to purify the paste. For this 

 purpose, a quantity of lyes at 80 B. being poured in, the mass is heated, worked well 

 with a rake, then allowed to settle, and drained of its lyes. A second service of lyes 

 at 4 B., is now introduced, and finally one at 2 ; after each of which there is the 

 usual agitation and period of repose. The pan being now skimmed, and the scum or 

 fob removed for another operation, the soap is laded off by hand-pails into its frame- 

 moulds. A little palm oil is occasionally employed in the manufacture of yellow soap, 

 in order to correct the flavour of the resin and Brighton the colour. This soap, when 

 well made, ought to be of a fine wax-yellow hue, be transparent upon the edges of 

 the bars, dissolve readily in water, and afford, even with hard pump-water, an 

 excellent lather. 



The frame-moulds for hard soap are composed of strong wooden bars, made into the 

 form of a parallelogram, which are piled over each other, and bound together by 

 screwed iron rods that pass through them. A square well is thus formed, which in 

 large soap-factories is sometimes 10 feet deep, and capable of containing a couple of 

 tons of soap. For plain yellow or curd soaps, iron frames are now used instead of 

 wooden ones, in almost every factory. 



Mr. Sheridan some time since obtained a patent for combining silicate of soda with 

 hard soap, by triturating them together in the hot and pasty state with a crutch in an 

 iron pan. In this way from 10 to 30 per cent, of the silicate may bo introduced. 

 Such soap possesses very powerful detergent qualities, but it is apt to feel hard and bo 

 somewhat gritty in use. The silicated soda is prepared by boiling ground flints in a 

 strong caustic lye, till the specific gravity of the compound rises to nearly double the 

 density of water. It then contains about 35 grains of silica, and 46 of soda-hydrate, 

 in 100 grains. 1 



Hard soap, after remaining two days in the frames, is at first divided horizontally 

 into parallel tablets 3 or 4 inches thick, by a brass-wire ; and these tablets are again 

 cut vertically into an oblong nearly square bars, called ' wedges ' in Scotland. 



The soap-pans used in the United Kingdom are made of cast iron, and in three 

 separate pieces joined together by iron-rust cement. The following is their general 

 form : The two upper frusta of cones are called curbs ; the third, or undermost, is 

 the pan to which alone the heat is applied, and which, if it gets cracked in the course 

 of boiling, may easily be lifted up within the conical pieces, by attaching chains or 

 cords for raising it, without disturbing the masonry in which the curbs are firmly set. 

 The surface of the hemispherical pan at the bottom, is in general about one-tenth part 

 of the surface of the conical sides. 



Tho white ordinary tallow soap of the London manufacturers, called curd soap, 



1 By the writer's own experiments upon the liquid silicate made at Mr. Gibbs's excellent soap factory. 



