HARD SOAP To Boil Hard process of making hard soap is similar to that of making soft soap by boiling, with the addition of steps taken to sepa rate water, glycerin, excess of alkali, and other impurities from the true soap, i. e., the alkali salts of the fat ty acids. As, this is the real process of soap making, it may be described in full. The best method requires three kettles, two small kettles to hold the lye and the fat respectively, and one large enough to contain both in gredients without boiling over. Put the clean grained fat, or the grease, in one of the smaller kettles, with suf ficient water or weak lye to prevent burning, and raise to a boil. Put the lye, or the solution of soda or potash, or both, in the other small kettle and dissolve in boiling water. Now place the large kettle on the fire and ladle into it about one quarter of the melt ed fat. Add an equal quantity of the hot lye, stirring the mixture con stantly. Continue thus, one person ladling and another stirring, until about two thirds of the fat and lye have been thoroughly mixed together. At this stage the mixture should be a uniform emulsion of about the con sistency of cream. A few drops of the fluid cooled on a glass plate should show neither globules of oil nor water separately, and a drop of the cooled liquid on the tongue should not have an alkaline, biting taste. Now add enough strong lye to complete the de composition of the fats and the re moval of the glycerin, and continue boiling until the mixture has a strong alkaline or burning taste. Add the remainder of the fat and lye alter nately, taking care that in the end there shall be no excess of lye.
Up to this point the process is sim ilar to boiling soft soap, and we have seen that to make soft soap of the mixture it is only necessary to evapo rate the excess of water by a boiling down process. The important dif ference in making hard soap is the addition, at this point, of salt, by means of which the creamy emulsion of oils and alkali is broken up. The
salt has a stronger affinity for water than soap has. Hence the salt takes the water and causes the soap to sepa rate and rise on the surface of the lye in a curdy, granulated state. The mother liquor or spent lye will be found to contain glycerin and salt with other impurities, but no fat or alkali. Hence glycerin is one of the important by-products of commercial soap making.
To Improve Hard Soap.—A better quality of soap may be made by re melting the product of the first boil ing and adding more fats or oils and lye as needed until the mixture has a decided taste of alkali, then boiling the whole until the process of saponi fication is complete.
If pure grained fat and good white lye are used, the resulting product will be a pure white hard soap that will be suitable for all household pur poses. The time required will depend on the strength of the lye, but usually from two to four hours' boiling is necessary.
Hard Soap.—The same ingredients are used in both soft soap and hard soap, and soft soap may be purified and hardened by boiling and by the addition of salt as above described. Glauber's salts (sulphate of soda) melted by fire in a thick iron kettle will harden soaps which would other wise be too soft. Add about 1 pound of fused salt to 20 pounds of the soap.
Stir 1 pound of potash lye into 1 quart of cold water until dissolved. Set aside until it is cold. Mix 2 table spoonfuls each of powdered borax and powdered ammonia into 1 gill of water. Melt with gentle heat 5 pounds of purified grained fat. Pour the cold lye gradually into the warm grease, and stir in the borax and ammonia, mixing and stirring vigorously for 15 or 90 minutes. Line a tight wooden box 'or pan with muslin or greased paper, and pour the soap into it to cool and harden. When hard cut into bars with cord or annealed wire. If the fat has been properly clarified, this soap is said to be dear and white and will float on water. It is a pow erful cleanser.