Textiles Mock Revision

AS Level Textiles Theory, for a mock exam.

Yarns, The Importance Of The Twist

  • A yarn is a continuous length of twisted fibres, either filament or staple.
  • In a yarn, different types of fibre may be used to create a yarn with the desirable qualities of the individual fibres.
  • (TPI - twists per inch) is a term used in the textile industry that measures how much twist a yarn has.
  • Twist in needed to hold the fibres together.
  • It is added in both the spinning and plying process (plying is twisting yarns together that already have twist eg. embroidery thread is a six ply yarn).
  • Fine wool and silk generally have more twist that coarse wool.Short staples have more twist than long filament fibres. Thin fibres twist more than thick.
  • A woollen yarn will have much less twist than a worsted yarn, because it has more air in it (the woollen, that is).
  • Weft yarns often have less twist than warp yarns, because warp yarns need to be stronger to withstand the tension of the loom.
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The Properties Of Silk

  • May crease easily
  • One of the strongest natural fibres but becomes about 20% weaker when wet
  • Not very elastic
  • Absorbent (has a moisture regain of about 11%)
  • Natural Lustre - due to rounded edge triangular cross section, which allows a lot of light to be reflected
  • Can be weakened if over exposed to sunlight
  • Poor conductor of electricity (makes silk good as a lining material, as static is what causes skirts etc to ride up)
  • Can shrink
  • Hard to care for in some cases eg. often needs to be dry cleaned
  • Stains easily
  • Cool to wear in summer, warm to wear in winter
  • Can be easily dyed
  • Natural protein fibre
  • Silk is very flammable
  • Used to be costly, but in recent years is actually not so
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Fabric Finishes

  • Fabric finishes improve appearance and/or properties.
  • Physical Finishes - where a machine or tool changes the fabric.
  • Chemical Finishes - where chemicals are used to change the fabric.
  • Biological Finishes - where bacteria and enzymes change the fabric.
  • Coated - where the fabric is coated on one side with a substance.
  • Fabric finishes can: enhance appearance, change texture, improve feel, improve drape, modify wearing qualities, modify care requirements.
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Physical Fabric Finishes

  • Brushing - wire rollers brush the surface of the fabric to give it a softer feel and a napped appearance.
  • Embossing - engraved rollers create a releif pattern on the fabric which changes texture and appearance due to pattern embossed.
  • Calendering - heavy rollers press the surface of the fabric which makes it smoother with improved sheen.
  • Pressing - presses smooth the surface of the fabric to give it improved handle and a smoother surface. This is often used on woollen fabrics.
  • Shrinkage - fabric is steamed and placed over a vibrating conveyer belt to reduce shrinking later in use and care.
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Chemical Fabric Finishes

  • Water repellent - silicone is spayed on to the surface of the fabric which allows air whrough but not droplets of water (these rest on the surface) however, this is NOT water-proofing a fabric because if there is a lot of water it will leake through.
  • Stain resistant - stain resistant resins are applied to the surface of the fabric which prevents dirt from clinging to the surface.
  • Crease resistant - fabrics are made crisper and more crease resistant by resins being applied.
  • Flame resistant - chemicals are applied to yarn or fabric which prevents them from easily igniting.
  • Shring resistant - fibre scales (found on wool) are removes with chlorine or blocked with resins to reduce shrinkage.
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Biological Fabric Finishes

  • Desizing - to prevent breakage during weaving etc. warp threads are given an adhesive coating, which can be harmful to the skin. Amylase enzymes (starchbreaking) are used to remove the substances that are harmful when weaving is complete.
  • Bio-Polishing - natural fibres can be given a smoother and glossier appearance with enzymatic treatment, which removes fuzz and pilling on the surface of the fabric.
  • Denim Finishing - cellulase enzymes can be added to denim to give it a stonewashed look. A small dose of enzyme can replace several kilograms of pumice stones. This is know as Bio-stonewashing.
  • Bio-scouring - prior to dying and printing, fabrics are sometimes scoured to make the process easier. Usually, harsh chemicals are used in this process which can result in a reduction of the weight of the fabric. To stop this, enzymes are used to complete the same task.
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Coated Fabrics

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Mood And Presentation Boards

  • Part of the initial design process
  • A collection of ideas that will fit together
  • Used as a scource of inspiration
  • Designers can see what will fit in with the final outcome and what wont
  • Helps to develope design concepts
  • Visual illustration for the style and feeling that one is persuing
  • Can include cut outs, sketches, fabric swatches, colours and other relevant images and words
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Fabric Insulation

  • Quilting - two layers of fabric are sewn, with wadding inbetween, in a  diamond pattern or any other random things that want to be sewn on. Quilting makes pockets in which air can be trapped for insulation.
  • Interfacing beween layers of fabric also provides an layers for insulation.
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Fabric Construction

  • Woven fabrics - Plain weave, Twill weave (denim, tartan, tweed), satin or sateen weaves (weft floats over four or more yarns to give a sheen), jaquard weaves (complex - patterns are woven in), pile weaves (exra layer of weft yarns to form loops). These weaves can be combined and varied. Woven fabrics do not fray untill cut as they have a selvedge. They can be woven and different densities and have different weights. The fabric is strongest on the grain line. The fabric can stretch on the bias (the diagonal).
  • Non woven fabrics - wool felt is produced by usinf short staple wool fibres. The scales of the wool interlock  and stay put. non woven fabrics are not very strong, can be made in a range of weights, do not fray, can be made from recycled fibres, can easily pill and are cheap to produce.
  • Bonded fabrics (non woven) - Dry laid (web of fibres is laid in a drum and injected with hot air to bond the fibres together), wet laid (web of fibres is mixed together with a solvent that softens that fibres and releases a glue like substance that bonds the fibres together and they are then laid out to dry), direct spun (the fibres are on a conveyor belt and sprayed with glues. they are then pressed).
  • Fleece is a woolen typr of fabric made from polyester. The fibres are spun in to a yarn which is woven or knitted and then the surface of the fabric is brushed with wire brushes.
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