An Extra Problem. - The life of the silkworm is an interesting story. If any girl has time to read about it she can make a report to the class. There is a list of references at the end of this chapter which will be helpful.
2. Under the microscope the silk fiber looks like a smooth glass rod. Occasionally markings show that are caused by the coating of the silk fiber, called gum or sericin which has not all been removed. See Fig. 82.
How to Know Artificial Silk. - You may find that some of your silk samples are not made of real silk but of artificial silk. You will be able to distinguish artificial silk by its very brilliant luster. Silk is such a beautiful and valuable fiber that manufacturers have made many attempts to find a cheaper substitute, and as a result we have artificial silk. Artificial silk is made by treating wood pulp or cotton waste with chemicals until it becomes a pulpy mass. This pulpy mass is then forced through tiny tubes. After the filaments have emerged at the other end of these tubes they harden and become what we know as artificial silk. It is cheaper to produce artificial silk than real silk but the fiber is stiff and not as strong as genuine silk. When subjected to moisture materials made from artificial silk become much weakened and great care must be taken in laundering them.
Examine your samples to see if you have any pieces of artificial silk. Ravel out a yarn and compare it with a yarn made of real silk. What difference do you find in their appearance and feeling? If you examine the artificial fiber under the microscope you will find that it looks like the drawing in Fig. 83. Artificial silk is sold under various names, fiber silk, artificial silk, wood silk and rayon. Your stockings, ribbons, your brothers' ties and many dress materials are often made of fiber silk.
An Extra Problem. - The girls who have time will find it interesting to study newspaper advertisements and list the articles which they find advertised as being made of artificial silk. It may be found under any of the names listed above.
How to Know Linen. - The linen fiber, like cotton, comes from a plant. However, it comes from a different part of the plant, the stem itself. The first picture in Fig. 84 shows the plant, called the flax plant, from which the linen fiber is taken. The field of flax plants looks much like a grain field as shown in the second picture.
Select the pieces from your collection of samples that you think are linen. Perhaps you will have a piece of an old handkerchief that is linen. Can you think of ways of describing the appearance and feel of linen as being different from cotton? 1. The linen thread as it appears in linen cloth has a slight irregularity caused by the unevenness of the linen fiber. Compare a piece of cotton cloth with linen and notice how regular and even the cotton is as compared with the linen. The linen is stiffer and wrinkles more easily than cotton. Can you think of words to describe the feeling of linen material?
2. Unravel a piece of linen yarn from a piece of linen cloth and try breaking it. Compare the strength with the strength of cotton. Untwist the yarn to get a linen fiber. The fiber is long and straight as compared with the cotton fiber. It has an average length of twenty inches, varying from ten to thirty inches. Picture 3 in Fig. 84 shows some linen fibers ready to be made into yarn. The waste from the manufacture of the linen fiber is called tow and is spun into a cheaper quality of linen yarn.
3. Under the microscope the linen fiber looks like a jointed bamboo rod. These joints are called nodes and the ends of the fibers are pointed. See Fig. 85.
Some Pages in Your Notebook. - Plan a page in your notebook for each of the five fibers that you have studied. Mount samples of cloth, yarns and fibers of each kind. Make a drawing of the way the fiber looks under the microscope and add notes about each fiber according to the following suggestions.
1. Where does it come from?
2. What particular characteristic of each fiber helps to spin it into yarn or thread?
3. How does the length of fiber generally affect the quality and texture of the finished cloth?
4. What did you learn about each fiber in your study of underwear material as to warmth?
5. What did you learn about each fiber in your study of underwear material as to absorption of moisture?
6. How does the structure of each fiber affect its laundering quality?
You may have learned things about these fibers in your study of geography or science that you can add to these pages.
Your notebook pages should be neat and well arranged. The same principles of design apply to the arrangement of a page in a notebook as to the arrangement of a room or the design of a dress. Ask your neighbors to criticize your pages for arrangement and neatness. Do not forget that criticism means favorable as well as unfavorable comments.
Suggestions for Reports on Special Topics. - You will find it interesting to make a study of how each of these fibers is produced. Five girls might each choose one of the five fibers on which she will report. Each girl should try to bring as much illustrative material as possible when she makes her report in order to make her talk interesting. It is often possible to obtain good illustrative material free by writing to manufacturers. There is a helpful list of references at the end of the chapter.