CHOOSING SOAP.

Star (Christchurch), Issue 19268, 3 January 1931, Page 20 (Supplement)

CHOOSING SOAP.

FOR TOILET USE OR IN THE LAUNDRY. To many housewives “soap is soap,” and little consideration is given to quality. Yet the manufacture of this product is a process entailing' high technique and skill. In a well-run factory both raw materials and final results are tested by fully qualified chemists and nothing imperfect is sent out. Good materials are of first importance. Soap is produced by the action of caustic soda or potash on certain fats and oils. Soda gives a hard ,and potash a soft soap. The fats and oils vary considerably, and it is these chiefly that decide the quality of the finished product. Cheap varieties are often made from partially rancid fats. To counteract the unpleasant odour that would naturally result strongsmelling perfumes are’ added. A highly scented soap, therefore, should at least be an object of suspicion. Quality Important. Given good materials the next step for the soapmaker is to see that the manufacturing process is carried out with perfect accuracy. A certain quantity of fat or oil requires a definite amount of alkali (soda or potash) to saponify it—that is, change it into soap. If there is too much fat the excess will be left in the soap unsaponified. Similarly, too much soda or potash will leave a residue of free alkali. Again, soapmaking is a slow process, and if it is not properly controlled the reaction may never be carried out to completion; thus both unsaponified fat and free alkali will be left. For cleaning and laundry purposes soaps containing a little free soda may be used, except for aluminium and for the washing of silks and woollens. It must never exceed one per cent of the dry soap, however, especially for clothes, as it disintegrates and breaks the fibres. Soap containing unsaponified fat is too greasy for laundry purposes. Alkali Hardens Skin. Toilet soaps must on no account contain free alkali either in the form of potash or soda, as it hardens the skin and may cause serious trouble. This is especially likely if the fat is also impure. Among the best oils for toilet soaps are palm, olive, and coconut. These should be combined -with potash. Medicated soaps are prepared by adding certain properties during manufacture ; the most common are carbolic acid, tar, oatmeal, boracic acid, and sulphur. An economical housewife dislikes intensely what she calls “paying for a name. Actually, however, one rarely does this. Firms of high standing have only obtained their position by pursuing a policy of unremitting integrity.