Shrinkage
by Bob Goffredo
Wonder why some fabrics shrink
and some carpet edges
ripple....!
Did you ever have a sweatshirt that shrunk? Is it now above your waist.
How about a pair of jeans
that got real tight after the first washing and shorter on the length. Like many other
purchases of natural fabrics that are made to be worn they may shrink now or
later. I have many tiny sweaters I use for
shining my shoes and polishing my car. How have you used your shortys???
A textile that can maintain it's original shape after use and care is said to have
dimensional stability. Manufacturers concerns are with residual shrinkage and
relaxation shrinkage. Residual shrinkage is what takes place over a period of time from
laundering and care, they are such items as linens and towels. Relaxation shrinkage occurs
when the strained yarns relax after the stress placed on them is released. When washing
these goods the fabric tension is relaxed and when dry they go back to their original
condition. Do you remember your mother or grand mother pinning a sweater to the bed to
retain is shape and size. At the time you didn't think much about it until your cleaned
your first oriental rug.
During the making of a woven rug the stresses placed on the warp yarns, (those are the
ones that are in the long direction), are under tension. When the rug is made wet during
cleaning the natural warp yarns relax and the edges will sometimes show waviness. The
tension takes place when the rug maker pulls the loom tight tucking in the weft or filling
yarns. In the making of woven goods the weft or filling yarns, (these are the ones that go
across the rug, weft to right) will have less shrinkage because they are knotted and have
less tension. In the making of fabric each operation can add various amounts of tension to
the fabric yarn. The yarns can behave like an elastic band which when stretched will
return to its original position, whereas the yarns that are stretched will return
gradually to the original position.
During fabric making a shuttle that carries the weft yarns darts back and forth across
and between the warp yarns with a lesser amount of tension while the warp yarns are under
tension throughout the production.. If you attended the meeting at the Maine fabric plant
in Webster, MA, you saw fabric being manufactured and how much tension is required
to produced today's fabrics.
Shrinkage treatments such as preshrunk fabrics, mercerizing in which the fabrics are
placed under tension and exposed to certain chemical solutions to prevent excessive
shrinkage. The blending of synthetic yarns with cotton will resist some shrinkage. The
manufacturers highly recommend reading the care instruction label sewn into each piece of
clothing.
This subject of shrinkage has been taken from the Textiles and Fabric and
can be found in most textile books in your favorite Library.
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