35. KINDS OF WATER.--Water is either hard or soft. As it falls from the clouds, it is pure and soft until it comes in contact with gases and solids, which are dissolved by it and change its character. It is definitely known that the last of the water that falls in a shower is much better than the first, as the first cleanses not only the air, but the roofs and other things with which it comes in contact. In passing through certain kinds of soil or over rocks, water dissolves some of the minerals that are contained there and is thus changed from soft to hard water. If sewage drains into a well or water supply, the water is liable to contain bacteria, which will render it unfit and unsafe for drinking until it is sterilized by boiling. Besides rain water and distilled water, there is none that is entirely soft; all other waters hold certain salts in solution to a greater or less degree.
The quality of hardness, which is present in nearly all water, is either temporary or permanent. Water is temporarily hard when it contains soluble lime, which is precipitated, that is, separated from it, upon boiling. Every housewife who uses a teakettle is familiar with this condition. The lime precipitated day after day clings to the sides of the vessel in which the water is boiled, and in time they become very thickly coated. Permanent hardness is caused by other compounds of lime that are not precipitated by boiling the water. The only way in which to soften such water is to add to it an alkali, such as borax, washing soda, or bicarbonate of soda.
36. USES OF WATER IN COOKING.--It is the solvent, or dissolving, power of water that makes this liquid valuable in cooking, but of the two kinds, soft water is preferable to hard, because it possesses greater solvent power. This is due to the fact that hard water has already dissolved a certain amount of material and will therefore dissolve less of the food substances and flavors when it is used for cooking purposes than soft water, which has dissolved nothing. It is known, too, that the flavor of such beverages as tea and coffee is often greatly impaired by the use of hard water. Dried beans and peas, cereals, and tough cuts of meat will not cook tender so readily in hard water as in soft, but the addition of a small amount of soda during the cooking of these foods will assist in softening them.
Water is used in cooking chiefly for extracting flavors, as in the making of coffee, tea, and soups; as a medium for carrying flavors and foods in such beverages as lemonade and cocoa; for softening both vegetable and animal fiber; and for cooking starch and dissolving sugar, salt, gelatine, etc. In accomplishing much of this work, water acts as a medium for conveying heat.
37. BOILING.--As applied to cooking, boiling means cooking foods in boiling water. Water boils when its temperature is raised by heat to what is commonly termed its boiling point. This varies with the atmospheric pressure, but at sea level, under ordinary conditions, it is always 212 degrees Fahrenheit. When the atmospheric pressure on the surface of the water is lessened, boiling takes place at a lower temperature than that mentioned, and in extremely high altitudes the boiling point is so lowered that to cook certain foods by means of boiling water is difficult. As the water heats in the process of boiling, tiny bubbles appear on the bottom of the vessel in which it is contained and rise to the surface. Then, gradually, the bubbles increase in size until large ones form, rise rapidly, and break, thus producing constant agitation of the water.
38. Boiling has various effects on foods. It toughens the albumin in eggs, toughens the fiber and dissolves the connective tissues in meat, softens the cellulose in cereals, vegetables, and fruits, and dissolves other substances in many foods. A good point to bear in mind in preparing foods by boiling is that slowly boiling water has the same temperature as rapidly boiling water and is therefore able to do exactly the same work. Keeping the gas burning full heat or running the fire hard to keep the water boiling rapidly is therefore unnecessary; besides, it wastes fuel without doing the work any faster and sometimes not so well. However, there are several factors that influence the rapidity with which water may be brought to the boiling point; namely, the kind of utensil used, the amount of surface exposed, and the quantity of heat applied. A cover placed on a saucepan or a kettle in which food is to be boiled retains the heat, and thus causes the temperature to rise more quickly; besides, a cover so used prevents a loss of water by condensing the steam as it rises against the cover. As water boils, some of it constantly passes off in the form of steam, and for this reason sirups or sauces become thicker the longer they are cooked. The evaporation takes place all over the surface of the water; consequently, the greater the surface exposed, the more quickly is the quantity of water decreased during boiling. Another point to observe in the boiling process is that foods boiled rapidly in water have a tendency to lose their shape and are reduced to small pieces if allowed to boil long enough.