BODYING of FIBERS, YARNS AND FABRICS
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Post 149 -by Gautam Shah
Fibers, yarns and fabrics have poor bulk or lose the bulk
during various treatments, are re-bodied by many different
substances. Bodying is also possible without any substantive
material application. Certain heat and water treatments shrink
the materials, increasing the bulk, whereas mechanical
(physical) manipulations also increase the apparent bulk.
Bodying is required to control the next process. Fibers (like silk)
are bulked to aid re-spinning or handling before the end stage
like stitching, packing and presentation or use of the material.
Bodying has strong effect on the suppleness (fall of curtains,
drapes, crease lines) and tactile feel of the material. It also
affects the thermal management (through heat exchange and
moisture movement). For curtains-drapery fabrics the bulking
governs the diffusion of view across, ‘modelling’ of the objects,
diffraction of light, masking and strength. For furnishing
fabrics and floor spreads the bulk, suppleness, direction of
texture, electrical behaviour, moisture absorption, dust and body
scale retention, and micro air movements over the surface are
important, and these are endowed by nature of such treatments.
Some of the prime techniques of bulking fibers, yarns and
fabrics are manipulative in nature like: leave behind
impurities, lints, staple fibers etc. by reduced carding, etc.,
mixing of different fibers before spinning, co-spinning (with
coarser fibers), twisting, mixed fibre weaving (with mixed for
warp-wefts), employing fabric formation techniques like
weaving, knitting, shrinking, perma-crease setting, singeing etc.
Another method of bodying is to add some form of gum or size
(simply starch), in the form of starch, gelatin, or resin or a
combination of these with lubricating substances such as oils or
wax. Some are temporary materials and are removed during
laundering. Cheap cotton or rayon fabrics are often heavily
starched for stiffness which after laundering may become quite
limp. Fabrics like organdy are permanently stiffened cottons.
The application of a carefully controlled acid solution causes the
surface of the yarn to become softened and a gelatin like. An
after wash in cold water causes the gelatinous outer surface to
harden forming a permanently stiffened exterior.
Raw silk contains, from 25 to 30 percent of its weight in sericin
or gum. And when the fiber is cleaned this substance is
removed. Silks may be weighted both to enable the producer to
regain some of the loss in fiber weight and to add greater body
to fabrics. The silk fabric is first placed in an acid solution of
stannic chloride (a chloride of tin). The fiber is allowed to absorb
the substance, it is then washed, placed into a solution of sodium
phosphate and then is washed again. During this process, an
insoluble compound (tin phosphate) is formed within the fiber,
and the weight and body of the fiber is increased. A further
treatment with sodium silicate solution forms another chemical
compound. The silk fiber can hold considerably more than its
own weight of this added chemical weighting. Heavily weighted
silks may have very poor abrasion resistance and eventually will
break from their own weight. Any silk labelled pure dye Silk
may not contain more than 10 percent of weighting, or 15
percent for black fabrics. If heavily weighted silks are burned,
a skeleton of the metallic compound in the shape of the woven
fabric is left behind.
Wool fabrics are fulled to give the fabric a more compact
structure. In a type of pre-shrinking, fabrics are subjected to
moisture, heat, soap, and pressure. This causes the yarn to
shrink and to lie closer together and gives the fabric a denser
structure. Wool cloth may be given more or less fulling, depending upon the desired characteristics of the resultant fabrics.
Melton cloth, for example is one of the most heavily fulled wool
fabrics and has a dense, felt like texture.
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