[Illustration: FIG. 146.--The test for shrinkage.] =Tests with microscope.= You have all seen the appearance of the fibers under the microscope. This reveals many things, and the unraveled fibers are easily identified. The microscope is the only sure test for telling cotton and linen fibers. One can sometimes discover shoddy mixed with the all-wool fiber because of the color. Shoddy is sometimes made of old colored woolen rags. =Tests for fading.= Pin a piece of cloth on a board with thumb tacks. Cover half with cardboard or heavy paper. Expose to the rays of sun for several days. Remove paper and notice difference. A piece can also be exposed near bright light, but not in sun's rays, to see the effect under ordinary wear. Marjorie Allen tested a piece of cashmere she was considering for a dress and decided not to buy it, for it faded quickly near the bright light. [Illustration: FIG. 147.--The test for strength.] =Tests for strength.= Try to break either warp or woof threads. Place the two thumbs together and press down on the cloth which should be held firmly in the hands. Try both sets of threads. Sometimes a weak warp or woof can be discovered. =Tests for shrinkage.= Barbara Oakes had a white cotton dress last year which never seemed to stop shrinking. Sometimes we can test materials for shrinkage. Measure width and length of sample to be tested. Wash it in hot water and soap. Dry and measure again. Is it narrower and shorter? In planning for cotton or woolen garments allowance should be made for shrinkage. [Illustration: FIG. 148.--The chemical tests show many things of use in judging materials.] =Chemical tests.= Chemicals are used for identifying fibers. Have you learned in your eighth grade studies about acids and alkalies? Have you studied at all about chemicals? It is possible to discover the composition of woven materials by testing them with chemicals. This is because acids and alkalies affect vegetable and animal fibers in different ways. Look up the difference between acids and alkalies. Study with your teacher and try to discover some of the common food and cleaning materials which we use every day in our homes which are acid or alkali. Some of these teach us we should know what the soaps and washing powders which we use will do to our clothes. Your teacher will provide some chemicals for testing. It is easier to test samples of cloth if they are fringed at the edges. Here are directions for some chemical tests: 1. Place a piece of white cotton cloth and a piece of woolen material in small dishes. Cover with 50 per cent solution of nitric acid. The wool fibers will turn yellow. The cotton remain white. If a piece of wool cloth was mixed with cotton, how would the test prove it?