ually test yarn and fabrics by means of an
instrument called a dynamometer. In this way one can find out whether
a yarn or fabric comes up to the necessary strength, and whether it
has the required yield or stretch. Both these points are of importance
in practical work, for it is essential that the yarn as shown should
at least be strong enough to bear the strain of manufacture. The test
is made by stretching a hank of yarn between the two hooks of a cloth
testing machine. The handle at the side is now turned, so that the
lower hook descends and puts a strain on the hank. This strain is
increased, and at the same time the pointer moves around the dial,
which indicates in pounds the amount of strain. When the threads of
the hank begin to break, the strain is released, and the catch at the
side keeps the pointer in position until the amount of strain is read
on the dial. The distance stretched by the yarn before breakage occurs
is shown in inches and fractions of an inch, in the small indicator
arranged near the upper hook.

Test different fabrics and yarns.

=Experiment 53--Characteristics of a Knitted Fabric=

Apparatus: Pick glass.
Materials: Knitted fabric, woven fabric.
Reference: _Textiles_, page 153.

_Directions_

1. Examine a piece of knitted fabric under the pick glass and notice
the construction. How does it differ from weaving? The single thread
is formed into rows of loops which hang upon each other, thus giving
the knitted fabric its characteristic springiness. Why is hosiery
suitable for underwear? Try to obtain the thread of the knitted fabric
and reduce the whole to a heap of yarn by cutting it. Is the yarn
intact?

2. A knitted fabric may be told from a woven fabric by studying the
following sketch. (See page 310.)

Note that the element of stretch or elasticity is wholly lacking in
the woven cloth except what lengthwise elasticity may be in the
threads themselves. On the other hand, referring to the printed
diagram of the knitted fabric it will just as readily be seen that its
very structure implies such a corrugation of its individual loops that
if distended by force in any direction its tendency is to return to
the normal.

The essential characteristics of good hose are:

1. That they should be without seams.

2. That they should be so knit as to conform to the foot of the
wearer.

3. That they should be thickened or reinforced where the greatest wear
comes.

[Illust