Eugene Casole, age 11, of Flushing, New York, for his question:

What is meant by hard water?

Compared with a concrete sidewalk or other solid substances, no water in the world can be called hard. But some ground water is harsh and difficult to get along with, especially in laundries. Fresh rainwater is eager to form frothy bubbles of soapy lather and we call it soft water. The unfriendly ground water is hard by comparison. Its hardness is caused by mineral chemicals dissolved from underground rocks. As a rule, these invisible dissolved materials are calciums from soft limestone minerals. They are more easily dissolved than most of the earth's rocky minerals.

Calcium type chemicals are easy to dissolve in water and also easy to remove sometimes too easy. They tend to separate themselves and clog our plumbing systems with solid layers. They remove themselves from boiling water and deposit stony layers inside our kettles. Instead of reacting with soap to create lather, they separate themselves and leave grimy rings around the tubs. We can force them to remove themselves before the water enters our homes, merely by adding waterening chemicals. These salts and sodas sift out the hard water chemicals in a hurry.