There are three varieties of the tea-plant; both black and green tea can be prepared from them all. Green tea is made from young leaves steamed, roasted, and dried quickly on copper plates. Black tea is made from leaves which have been exposed to the air ten or twelve hours before roasting. The action of the air upon the leaves during this long exposure causes the dark color. Green tea gives up less of its juices in drying, and this accounts for its energetic action on the nervous system.
The tea-leaf contains the largest amount of nutritive matter of any plant used as human food, though only a small portion of it is extracted by our common method of making tea. There is a large proportion of casein in the leaves. Many of the savage tribes of Tartary boil the leaves with soda, and eat them with salt and butter. But in our method of using tea as a beverage merely, we use such a comparatively small quantity that the amount of nutriment is very little; its chief value being the sense of warmth and comfort that it gives. It excites the brain to increased activity, and produces wakefulness; hence it is useful to students and night-workers. It retards the action of the natural functions, causes less waste, and, to a certain extent, saves food. For this reason, when not used in excess, it is suited to poor people, whose supplies of substantial food are scanty; and to old persons, whose powers of digestion and whose bodily substance have begun to fail. It should not be used early in the morning, as the body needs immediate nourishment in a larger quantity; and it should at all times be taken moderately, both as to quantity and strength.
The water should be freshly boiled. Scald and heat the teapot, which should be of earthen or china, never of tin. Allow one teaspoonful of tea for one cup of boiling water. Reduce the proportion of tea when several cups are required. Put the tea in a strainer, pour through it half a cup of boiling water to cleanse the grounds. Then put the tea in the teapot; pour on the boiling water; cover closely and place it where it will keep hot, but not boil, for five minutes. If cold or lukewarm water be used in making tea, the thein, or nitrogenous substance, will not be obtained.
In boiling tea or allowing the leaves to remain long in the tea, by repeated steeping, the fragrant aroma is wasted and the tannin is extracted, which may cause gastric disorders to those who drink it. Never make tea in a tin teapot, as the tannic acid acts upon the metal and produces a poisonous compound.
A slice of lemon is a good substitute for milk in tea. The lemon prevents the headache and sleeplessness which the tea causes in some persons.
Make the tea by the first receipt, strain it from the grounds, and keep it cool. When ready to serve, put two cubes of block sugar in a glass, half Jill with broken ice, add a slice of lemon, and fill the glass with cold tea.