In finishing of materials, adulteration is sometimes practiced. In pressing cotton or linen, a luster is given to the surface. Cotton can be made to appear like silk or like linen, and is often sold for those fibers. Cotton can be napped in finishing and made to look woolly as in blankets or outing flannel, but it is still only cotton.
Fig. 144.—The microscope reveals many things.
How can clothing material be tested? These are the simple tests which the Pleasant Valley girls learned:
For sizing. This is easy to identify. Pick at the surface with your nail, and the starch or sizing will easily come off. Hang a wet piece in the air and see how the gloss looks then. This sizing often conceals defects in the cloth. These can be seen if the material is thin, by holding it against the light.
Fig. 145.—The test for fading.
Burning tests. The girls unraveled the fibers which Miss James gave them and tested wool, silk, cotton, and linen. They tried both warp and filling threads. They burned them with a taper. The animal threads (which are they?) burned slowly, charred, and smelled like burned feathers. Silk burns to an ash, except when weighted. Then it burns more slowly. When very heavily weighted, the flame does not burn readily and the form of the silk will remain. The vegetable fibers, cotton and linen, burn quickly and with a flame.
Fig. 146.—The test for shrinkage.