MATERIALS AND HOW TO TEST THEM
but in drying again it recovers its original strength. Normally it is about one-half as strong as silk and has almost no elasticity.
To Determine the Kinds of Fibers in Cloth: Perhaps most of us think we can recognize an all wool, all silk, all cotton, or all linen fabric by its appearance and feel. Sometimes we can. But to recognize a material in which the cotton and linen fibers have been carded in the same yarn, or to tell silk from artificial silk, silk from mercerized cotton, new wool from shoddy, or to detect the presence of a very small amount of wool, cotton or silk in a fabric, is a more difficult problem than the eyes and fingers alone can solve.
Different kinds of fibers are now so cleverly mixed and woven that the microscope and chemical tests are the only means by which one can accurately determine the fiber content of a piece of cloth. Some of tae chemical tests are very simple and can be readily performed in the home.
Animal and Vegetable Fibers: The fibers described in the preceding paragraphs fall naturally, according to their origin, into two groups, animal fibers (wool and silk) and vegetable fibers (cotton, linen, and artificial
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