2. How would you dress to go skating on a cold, windy day?
The Fiber That Keeps You Warm. - The kind of fiber from which a garment is made also has much to do with the saving of heat. This is especially true in undergarments which lie next to the skin. A fiber which is a poor conductor of heat makes a warm garment because the heat can not escape.
The wool fiber is the poorest conductor of heat of all the fibers used for clothing. It makes a very warm garment. The sheep from which we get the wool fiber wears a woolen fleece for the same reason that we wear woolen clothing, in order to keep warm. The sheep lives out-doors all the time and requires a warmer coat of wool than we do, who live in heated houses and buildings. Sometimes woolen underclothing is too warm for those of us who live in well heated and sometimes overheated houses. It is as bad to overheat the body by too much clothing as to wear an insufficient amount. For this reason most people find it better to wear cotton underclothing and depend on woolen dresses and outer wraps to keep warm when out-doors.
Since wool is sometimes too warm for everyday wear, underwear is also made from other fibers. The silk fiber is a better conductor of heat than wool. This means that heat escapes through silk more readily than through wool and will not keep the body as warm. However, silk is expensive and consequently is not worn by the majority of people.
Cotton is a still better conductor of heat than silk, permitting the heat from the body to escape readily. For those of us who live in well heated houses or warm climates, cotton makes comfortable underwear. Since it is a cheaper material than silk and satisfactory as far as warmth is concerned we find that most people wear cotton underclothing.
The material that is the best conductor of heat is linen. Heat escapes more readily through linen than through any of the other fibers used for clothing. Linen is not worn as underclothing by the modern girl but her great-grandmother had many linen undergarments.
For Class Discussion. - Ask yourself the following questions and then compare your answer with the answers of the other girls in the class:
1. Considering the amount of time you spend out-doors in winter and the way your home and school are heated, do you think you should wear woolen underwear?
2. Why do many people find it best to wear cotton underwear all year around?
3. How many woolen things do you wear when you are outdoors in winter?
Another Way That Clothing Prevents Too Rapid Loss of Heat. - One way in which the body loses heat is by means of evaporation of moisture. You may be surprised to learn that the body gives off about three pints of water in perspiration every day. Usually this water evaporates from the pores of the skin and we are quite unconscious of it. If anything happens which causes very rapid evaporation of this moisture we feel cold because the body loses heat so rapidly. For example, if we exercise strenuously and then sit down to rest in a breezy place we will soon become thoroughly chilled. The moving air causes the perspiration to evaporate quickly and this lowers the temperature of the body. This rapid chilling of the body can be prevented by putting on an extra garment as soon as one sits down to rest. Have you ever noticed that the football player or the basket ball player puts on a blanket or sweater as soon as he comes off the field after playing? If the body temperature is lowered it makes it easy for us to "take cold."
Too Warm Clothing Is Unhealthy. - Some people dress so warmly that it causes more perspiration than is normal. For example, children often wear heavy, woolen underwear that is unnecessary in well heated houses. This causes increased perspiration. Underclothes may absorb this perspiration and become damp. Do you see why this may cause them to "take cold" easily? Have you ever been told to take off your coat or sweater while you were in a heated room because you would be cold when you went out again? Are you able to explain why this is true? Have you ever noticed that when you leave your rubbers on while you are in the house that your feet become very warm? This, of course, is because the air is prevented from getting to the feet by the rubbers and evaporation of the perspiration does not take place. Then when you go out-doors again your feet being wet will become very cold.
Clothing That Helps Moisture to Evaporate Properly. - Porous, open mesh underwear permits the air to circulate over the skin and allows evaporation. A close-woven fabric worn next to the skin does not permit as much evaporation. For this reason the knitted union suit is much more healthful than the close-woven muslin suit. How will rubber garments affect the evaporation of perspiration from the skin?
For those people who exercise and may perspire very freely, it is important that the undergarment should dry quickly if it becomes wet with perspiration. Some fibers dry more quickly than others.
An Experiment to Do. - Find out whether a wool stocking or a cotton stocking dries more rapidly. Wash the two stockings and hang them up next to each other. Record the amount of time that it takes each to dry. If an undergarment remained wet with perspiration for a long time it might cause a feeling of chill. Do you think wool or cotton underclothing is more desirable in respect to this point?
The Danger of Wet Clothing. - We have already learned that the body loses heat by evaporation of moisture from the skin and if this evaporation is too rapid that the body temperature is dangerously lowered. Clothing that is wet conducts heat away from the body much more rapidly than dry clothing. This is true because water itself is a good conductor of heat. For these reasons damp clothing is always dangerous and especially so on cold, windy days. Do you now understand why it is so important to change your shoes and stockings when you get your feet wet? Or why you should wear your rubbers? Is it just as important to change your clothing if it becomes wet when you are caught in a rainstorm as if it becomes wet with perspiration? What would you do if your clothing became wet and you could not immediately secure dry clothing? Keep walking, running or exercising vigorously in order to make the body produce more heat.