BODYING of FIBERS, YARNS AND FABRICS

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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WEIGHT and TRANSLUCENCY of fabrics for curtains

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Post 104 - by Gautam Shah

WEIGHT and TRANSLUCENCY of fabrics for curtains

Weight and Translucency of a fabric are two key factors for its suitability as an opening’s treatment material. Though both are co-related in that a heavy fabric is more opaque, and a translucent fabric is likely to be lighter, yet many contradictions exist. For the favour of one aspect the other can be manipulated. The final determinants for suitability of a fabric material for covering an opening depend on Treatments over a fabric, mode of hanging and pleating, presence or absence of a liner layer and the secondary treatments over the opening itself.

Fabrics are light because the fibres are thin or can be spun very finely, are filaments or long staple in nature and woven with a single weave or similar techniques. Fabrics or fibres dyed to lighter shades seem less heavy. The illumination conditions of the interior space, and the viewing position in the interior or exterior location, substantially affect the perception of transparency. A bright exterior or one that allows greater proportion of ‘sky component reflection’ (the reflected light from the sky) such as on sea coast, very vast open grounds, on upper section of windows tall buildings, and very bright or highly a reflective frontage of urban streets, all contribute to the brightness of window-backside (an exterior side). A bright exterior side and a glare-less interior, both add to the translucency. A glare is less dominant, when areas besides the curtain are reasonably illuminated or furnished in lighter shades. A direct sun-light exposure of the window makes the curtain seem opaque (at least from outside).

The perception of transparency is governed by the construction of the curtain, such as pleats, fall, back-layering, and the direction of the weave. The natural form of the fabric for curtain forming is the warp forming the vertical orientation (and the weft the horizontal position). A curtaining system, called Rail-roallng, places the fabric, with weft forming the vertical orientation (and warp the horizontal position), makes the fabric seem more opaque. Curtains are also formed with fabrics of two colours or textures. The central or edge sections are formed with lighter (or white) fabric, allowing more light, feeling of lightness and view-through facility. 

SHEERS: A sheer fabric is very thin material which make it very translucent. Sheer curtains are known as privacy curtains. Some of the best sheer fabrics are of pure silk, but most of the commercial materials are made of synthetic filament yarn (long length fibres). Lattices like airy or net woven fabrics are so pliable, flimsy and semi-transparent that they behave like a sheer fabric curtain. A sheer fabric has a natural graceful fall and allows light to filter through. Sheer fabric curtains nominally form the first layer in multiple curtains system. Such curtains allow a fuzzy view during day time, but at night may require an opaque topping of a curtain. Sheer fabric must not be used with a lining fabric to maintain its translucency. Sheer fabrics come in a wide variety of colours, but white and natural shades of whites, such as off-whites, cream, and ivory are popular. Sheer fabrics are also embellished and embroidered for patterns. Such extra work, however, increases the weight of the fabric at the cost of graceful fall. Sheer fabrics are commonly heavily pleated and so the total quantity of cloth required for a sheer curtain is little more then a curtain of regular fabric. Sheer fabrics, due to their thin body and the lattice like weaves, offer very little insulation.

Historically translucent fabrics used for lighter curtains include Chintz, Cretonne, Gauze, Muslin, Nets or Netting. Fibers with rough texture through raised 'hair' (fibres from short staple cotton, combing and carding wastes) break and distribute the light, it all directions. Where the fibers have a natural tinge (dull-white -typically unbleached cotton) than the interior face of the curtain glows in sun-light. In such a situation the fineness of fabric becomes less relevant. 

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STAGE CURTAINS

Stage curtains are used to cover the performance as well as backstage areas from the audience. Plain opaque, translucent or scenic curtains and fixed curtained panels are used to divide the performance zone. Proscenium stages use many types of curtains than arena or thrust-out stages. The main or the first curtain on the audience side is called a grand drape, act curtain, house curtain, house drape or main drape. These are made of heavier fabric.

The curtains are either dropped downward or moved sideways. In smaller theatres curtains have two leaves which part away horizontally. In larger theatres the curtains are suspended from a batten or staff and dropped down. The curtains open vertically a guillotine reveal -after the execution device, by moving into the fly tower. The curtains are (flown in theatre terminology) dropped or raised up to a required height masking the upper section of the stage. The dropping is quickest way of lowering a curtain. A single curtain which moves horizontally is called a wipe. A tab or tableau curtain has two overlapping leaves which are lifted from the corners in a diagonal direction. This forms a draped effect when it is opened. Austrian, braille or contour curtain is lifted through several vertical runners attached the back of the curtain. The curtain has set of circular segmental folds. A Venetian or profile curtain is similar in appearance to the Austrian drape, but each individual pleat can be raised independently, allowing the curtain to be opened to various heights or configurations. A scrim is a curtain made of a gauze like fabric that seems to be opaque when lit from the front and transparent when backlit. A backdrop curtain is a painted or scenery curtain forming the back surface of the performance area. A cyclorama is a large white curtain that encircles the stage and provides a background.

The depth of the performance stage is divided into zones with curtains. Very often such curtains are gestural to denote a break or end of an act though most are made from black or other dark coloured, non light reflective materials. A curtain call is a curtsey or thanks call offered beyond the closed position of the curtain, but in front part of the stage. Side wings are fixed curtains to obscure side sections of a stage. Curtains or head-wings are used to hide the upper section stage properties such as the hanging gears, ropes and rolled or folded section of the curtains. Main curtains were first drop curtains but these required a heavy bottom staff. As this was hazardous, roll curtain was soon adopted. ‘Curtain was raised after the prologue and remained up throughout the performance, all scene shifting was in view of the audience. It was not until 1750 that an ‘act drop’ was used; previously, even intermezzi were performed in front of a full stage setting’.