A number of materials for softening water are on the market. The cheapest and best of them are alkalis, known as washing-soda, lye, borax, and ammonia. In softening water, the objection to the use of any chemical is the injury it may do to the fabric.
Washing-soda (sodium carbonate) is the best alkali to soften water for general household use, for, while effective in its action, it is not so corrosive as to render its handling difficult or its use unduly harmful, nor is it expensive. It should never be used in its dry form, however, for it is an alkali sufficiently strong to eat holes in a fabric if it is used in full strength, and wherever a particle of the dry substance falls, a strong solution is formed. Carelessness causes many of the complaints against present-day laundry methods.
Lye (sodium hydroxide, or caustic soda) is an alkali of far greater strength than washing-soda; one pound of lye being equal to about twelve pounds of washing-soda, it should be used with just so much the greater caution. It should never be used save in solution and, as the solution deteriorates very rapidly on exposure to air, if any quantity is made it should be kept in bottles or jars tightly stoppered with rubber stoppers. The compound formed by exposing lye to the action of air and water, is washing-soda, so there is no advantage in using it. Lye is much more difficult to handle, and its action is so much more corrosive than is that of other alkalis that it is not advisable to use it in the home laundry.
Borax (sodium biborate) is one of the mildest alkalis to use in the laundry. This alkali is more expensive than either lye or washing-soda and is not so vigorous in its action; but in some instances it is greatly to be preferred. Washing-soda and lye, unless thoroughly rinsed from clothing, have a tendency to cause yellowing, particularly when starch is used afterward. Borax, on the other hand, has a tendency to whiten fabrics and is added directly to starch, in order to give it good color and to increase its clearness. When colored fabrics or wools are to be washed in hard water, borax is one of the best alkalis to use for softening the water.
Ammonia (ammonium hydroxide) is another good alkali for softening water when it is not advisable to use stronger alkalis. Ammonia is a very volatile substance, consequently it should be used only when the laundry process is to be conducted quickly. It is better and cheaper to purchase the full-strength ammonia from a druggist and then dilute it, than to buy the article known as household ammonia, which is of unknown strength.