ENHANCEMENT OF MATERIALS Flashcards
textiles dyeing
involves the permanent application of a colourant to a fabric to give a uniform all over colour.
what does the colourant need to be successful
it must be able to be absorbed by - or react with - the textiles fibre. it must also be soluble so it can go into the spaces between the fibre molecules
what is a Vat
a very large-scale dye bath that contains dye liquor
what is in dye liquour
dyestuff, water and chemicals that help the dye attach itself to the fabrics. it is also heated to further help the dye penetrate the fibres.
when dyeing in a Vat, how does the fabric turn out
gives the fabric a solid all-over colour
three basic steps of the dyeing process
- immerse the dye into the Vat
- dye attaches itself to fibres
- fix the dye within the fibre - fabric is typically moved continuously so that the dye attaches itself evenly
why is the excess dye removed and cleaned with detergents once the fabric has reached a desired colour?
if this is not done, the fabric may develop faults such as losing colour when washed or streaking of the colour.
what can dyeing also be about and what type techniques can achieve this
removing colour or preventing colour from going onto the fabric. This can be achieved by using discharge or resist techniques
discharge technique explained
using a chemical deactivator to remove colour from the dyed fabric with a design painted on that has already been dyed, and the deactivator removes the colour completely leaving the design in an off-white or lighter int of original colour.
resist technique
involves the fabric being printed with chemicals that prevent dye being taken up in the chemically treated areas
what are other resist techniques typically used typically in commercially produced fabrics
- tie dye: fabric is twisted, knotted or folded and tied with band to prevent dye from reaching parts
- Batik: uses wax to prevent dye from colouring the fabric
there are many different stages in which dye can be applied. when is the dye applied with spin or dope dyeing?
dye is added to the spinning solution of man-made fibres before spinning the fibre - this leaves the fabric has good light and wash fastness
when is the dye applied with stock dyeing?
the fibres are dyed in loose form before being spun into a yarn, this avoids uneven dyeing
when is the dye applied with yarn dyeing?
yarns are dyed before being made into fabric. gives them good fastness to washing and wearing.
when is yarn dyeing often used
for high quality products or to produce certain colour and pattern effects like checks or stripes
when is the dye applied with fabric dyeing?
woven or knitted fabrics are dyed in long lengths
when is the dye applied with garment dyeing?
ready made garments like t-shirts are dyed as required, allowing manufacturers to apply colour last minute or responding to consumer demand
dye fastness / colour fastness
is the ability of a fibre or fabric to retain dye during manufacturing processes and during the care/use of the product by a consumer
how can degradation of the colour occur
- fading
- crocking
- bleeding
what do fabrics need fastness for…
- washing
- dry cleaning: solvents sometimes cause fading
- light: curtains need to resist sun bleaching
- perspiration
- rubbing (crocking): e.g knees of jeans
- bleaching: dye must resist chlorine in swimwear
what are colour trend predictions
colour forecasters analyse and interpret the moods and preferences of consumers, so they can make accurate predictions about the colours that will be popular at least one year ahead of the fashions.
in which dyeing stage will the choice of colour have to be made much earlier
dyed yarns
what stage makes a more economical response to market demand using JIT manufacture
piece dyed remain in their greige state until they are needed to be dyed a specific colour.
degradation meaning
the gradual breakdown of a dye leading to loss of colour in a product
dyeing
the permanent application of a colourant to a fibre or fabric, to give a uniform, all-over colour
dyestuff
a coloured substance used to add colour to textiles material
printing
a process of creating a design on fabric through the application of colour
surface decoration
any form of decoration put onto a ready-made fabric to add colour and/or texture
advantages of printing over dyeing
- there is a greater scope for designing
- more colours can be used in the design
- complicated designs can be produced
- the methods of printing are varied
- it is usually less costly than dyeing
what do the dyes used for printing need to be made into
viscose paste using thickener such as starch gum or alginate.
what is the stage a fabric is referred to as when it is not ready to be dyed or printed on
the greige stage or loomstate cloth
what impurities in the fibres (especially natural), need to be removed before a fabric is dyed or finished
fats, waxes, salts, oil, dirt and starch added to strengthen yarns before weaving
name three important preparation process for fabrics
- desizing
- scouring
- bleaching
describe desizing
washing the “size” off fabrics with water as they are typically soluble
describe scouring
this removes fatty and waxy impurities that would prevent the fabric from being ‘wetted’.
this involves washing the fabrics in solvents to remove the oils and greases, cotton is boiled and wool is moved through warm detergent solutions.
describe bleaching
makes sure fabric is evenly white before colour is added. Natural fibres tend to have a more off-white tone, whereas synthetic fibres are always white and do not require whitening treatment
what factors determine what printing technique to use
- quantity of the fabric to be printed
- effect required
- cost of the process
direct printing technique
the design is printed directly onto the fabric
discharge printing technique
the fabric is dyed then printed with paste that contain chemicals that destroy the dye in areas according to printed design
hand (block and stencil) printing technique
Block printing is the process of carving patterns, shapes and designs into a ‘block’. then printing paste is applied and pressed onto fabric.
stencil is a piece of. card with the design cut out, the printing paste is applied with a roller falling into the pattern gaps.
Both processes are very slow and not commonly used for commercial use.
rotary/flatbed screen printing
Rotary Screen Printed fabric involves pressing printing paste or ink through mesh on a cylindrical screen onto fabric. It involves a screen which is engraved for each colour, and loaded into our rotary screen printer for high speed and high quality textile printing.
used commonly for commercial use as its fast and more cost-efficient
transfer/dye sublimation
Dye-Sublimation Printing (or dye-sub printing) is a computer printing technique which uses heat to transfer dye onto materials
digital printing
Digital printing is the process of printing digital-based images directly onto a variety of media substrates.
Quilting
a functional and decorative technique that gives texture and form to fabric
the english quilting technique involves adding a layer of wadding between two fabric pieces, why?
it traps air so the fabric acts as an insulator and added thickness for a more protective fabric
what can quilting be paired with to give a more decorative effect
patchwork
what is italian quilting
its purely decorative and does not add warmth to a product. it is based on parallel lines
what is the other method of decorative quilting
trapunto - padding small enclosed areas of a design
what is embroidery
embroidery is a surface decoration technique that adds colour and texture to a fabric using threads and yarns to make stitches and various combinations
what are the two types of embroidery?
hand and machine embroidery
hand embroidery - 4 types of embroidery stitches
- flat stitches, simple and straight (E.G back, running and satin)
- linked stitches, loop of one stitch is linked to another (E.G chain and feather stitches)
- looped stitches, loop of the thread passes around needle and interlinks with the next (E.G fly stitch)
- Knotted stitches, thread twisted around needle (E.G french Knots)
how are embroidery threads different from sewing threads
usually they are thicker
what is the special needle needed for hand embroidery
crewel needles with sharp point and longer eye so thread easily passes through
what other piece of equipment is used for embroidery and why
an embroidery ring which holds the fabric tightly to stitches don’t cause the fabric to pucker
what are the two basic types of machine embroidery
- pre-programmed stitches
- free machine embroidery
pre-programmed stitches (for normal machines and embroidery machines)
normal machines - lots of pre-programmed decorative stitches can be combined and used to make interesting effects
dedicated embroidery machines - many designs are stored in the computerised machine or user can develop their own and upload it, it automatically creates the design onto the fabric.
free machine embroidery
the sewing machine foot is removed and a free machine embroidery foot is fitted, the fabric can move freely according to users desired pattern, fabric should be help taut and flimsy fabrics should have underlining or interfacing for support
what can be added to embroidery to enhance a garment even more
additional trimmings and components like beads and sequins can be added
