Wool, the second fiber in amount used for clothing, is an animal fiber
and differs greatly from the vegetable fibers discussed. Wool from the
sheep’s back differs from hair of goats or other animals in several
ways. Wool is very curly, and possesses a scaly structure in a much
more marked degree than hair, in which the external scales lie flat.
The surface of wool has sometimes been compared to a pine cone, or the
scales of a fish, although these two are quite different. The scales on
the wool fiber when moist and warm stand up, more as the pine cone, and
when cold and dry or cold and moist, lie flat. This peculiar structure
of the surface of the wool fibers gives them the property of felting,
or matting very closely together. Wool is also quite elastic, although
it has not great strength.
Since the demand for woolen cloth far exceeds the supply of new wool
there are many devices for making the supply go a long way, and
consequently many methods for deceiving the buyer. In adulterating a
material the manufacturer seeks a material cheaper than the fiber he
wishes to adulterate, one which can be concealed readily. Wool when
combined with the cheaper cotton fiber makes a material which wears
well, but does not keep its shape as well as all-wool cloth, is less
warm, and should of course receive a lower price than all-wool.
Because of the felting property of wool it is quite possible to conceal
a good deal of cotton under the surface of the woolen cloth, and when
the fibers are mixed before the threads are spun the task of detecting
them becomes doubly difficult.