Woven Fabrics - Fairchild Books

Fabrics made from worsted yarn are not necessarily
better than fabrics made from woolen yarn. Each kind
of yarn is suitable for a specific type of fabric. Tweed is
an example of a woolen fabric; gabardine is an example
of a worsted fabric. There are expensive woolens as well
as expensive worsteds.
The following are additional facts about woolen
and worsted yarns:
u Fabrics of woolen yarn are more important in
heavy winter coatings, ski sweaters, and blankets
because woolens generally provide better insulation
than worsteds. The fuzziness and soft bulkiness of
woolen yarns provide the dead air spaces needed for
better insulation.
u Because worsted yarns are more tightly twisted
than woolen yarns, fabrics of worsted yarn are usually
firmer and denser than fabrics of woolen yarn.
The more tightly twisted yarns help worsted to
hold its pressed creases and generally to better keep
its shape between cleanings than fabrics made of
woolen yarn.
u Fabrics made from worsted yarn usually show the
yarns and weave clearly and sharply on the face of
the fabric. Fabrics made from woolen yarns, on the
other hand, may have a napped surface or look like
the surface of felt.
Worsted fabrics, such as gabardine and serge used in
trousers and suiting, tend to develop a shine with wear.
Because the yarns are very smooth and tightly twisted,
pressure on the fabric (e.g., from sitting) and rubbing
tend to flatten the yarns and produce the luster. A popular
suiting fabric known as unfinished worsted is given a
light napping and fulling finish, which tends to cover up
the yarns (see p. 205). Thus the appearance of the yarns
and the weave are more subdued and the shine problem
is eliminated or greatly reduced. (Unfinished worsted is
a misnomer because the fabric is, in fact, given extra
finishing treatments.)
Single and Ply Yarns
Yarns are also categorized as single or ply. When a ply
yarn is untwisted, it separates into two or more finer
yarns. As shown in Figure 4.7, when a single spun yarn
is untwisted, it comes apart. Ply yarn, therefore, may
be defined as two or more single yarns twisted together
to form one new yarn. Two-ply yarns are two singles
twisted together, three-ply are three singles twisted
YARNS AND SEWING THREADS
A 73 F
a b
Figure 4.7
(a) Single spun and (b) ply yarns.
together, and so forth. Most ply yarns used in clothing
are two-ply. Little is gained by using yarns of higher
ply. If a yarn is not ply, it is referred to as single, never
single-ply.
Advertisements of two-ply worsted suiting and of
2 × 2 broadcloth shirts aim to indicate quality. 2 × 2
broadcloth shirts have two-ply yarns in both warp and
filling. In a 2 × 1 broadcloth, the warp is two-ply and
the filling is single.
In a ply yarn, two or more finer yarns are usually
twisted to produce the same thickness as a single yarn,
but with many additional benefits. In spun yarns, each
fiber can wind more times around a thinner yarn and
so hold more firmly. In plying the finer-spun yarns,
more twist is added, holding the fibers more firmly in
place and making the yarn stronger. Spun yarns are not
perfectly even in diameter. By twisting together two or
more yarns, the thin, weaker spots are reinforced. Thus,
plying improves spun yarns because the fibers cannot
slip as easily, the yarns are stronger, the yarn diameter
is more uniform, and there is a reduced tendency to pill.
Most single yarns have a Z twist. When plied with
another single yarn, an S twist is used. Open end yarns
(see p. 74) always have a Z twist. Ring spun (see p. 74)
and air-jet (see p. 74) usually have a Z twist, but the system
can produce S twist if modified.