enhancement of materials-1.5 Flashcards
what are the three stages of dyeing?
- immersing the fabric in soluble dyestuff
- the dye attaching itself to the fabric through absorption or a reaction with the fibres
- fixing the dye so the colour remains in the fabric
large scale dyeing is done in dye baths called…
vats
what is vat dyeing?
large scale dyeing
how is vat dyeing done?
- the vats are filled with dye liquor and the fabric is dyed in batches
- the fabric is agitated in the vat to ensure an even dye distribution/penetration
3.excess dye is removed and the fabric is washed with detergents and dried - washing helps avoid later colour loss
discharge dye…
removes colour from a dyed fabric using a colour destroying deactivator that bleaches out white or light patterns on the darker colour background
resist dyeing…
creates patterns by preventing colour from going onto certain areas of the fabric using a resist such as a string or elastics etc
what are the four types of resist dyeing?
-batik
- tie-dye
-shibori
-tritik
what is the process of tie-dye?
involves wrapped, folded and tied areas on a fabric which makes it difficult for the dye to be absorbed here. Multi-coloured patterns can be achieved by refolding/tying/wrapping the fabric and dyeing with another colour.
what type of fabrics does tie-dye work well on?
natural fibres
what is the process of batik dyeing?
patterns are applied by hand using melted wax or paste using a brush or tjanting tool. once dried, the painted areas prevent the dye from going onto the fabric. the fabric can be submerged in a dye bath or painted with different coloured dyes. After this, the wax or paste can be removed.
what is the process of tritik?
fine, running stitches can be applied to a fabric, then pulled tight before dye is applied. After dyeing, stitching is removed, revealing a pattern.
what are the advantages of tritik?
-good for intricate designs
-works well on natural fibres
what is the process of shibori?
Japanese method of folding or tying fabrics, then applying a combination of heat and dyes, or chemicals. When fabric is dried, the ties are removed. Works on all types of fibres and fabrics.
what are the 5 different stages in which dye can be applied?
-dope/spin dyeing
-stock dyeing
-yarn dyeing
-piece/fabric dyeing
-garment dyeing
what is dope/spin dyeing?
where man made fibres are coloured before fibre extrusion- the dye is added to the spinning solution/dope which makes it part of the fibre
what are the advantages of dope/spin dyeing?
-gives the finished fibres excellent light and wash fastness
what is stock dyeing?
-fibres, also known as stock, can be dyed before they are spun into a yarn
what is yarn dyeing?
the yarn is dyed before construction into woven or knitted fabrics.
what does dyed yarn enable for?
for the production of multi-coloured, patterned fabrics such as stripes, checks and jacquards
what is the one disadvantage of dyeing yarn?
-dyeing at this early of a stage commits the manufacturer to a fabric colour
what is piece or fabric dyeing?
manufacturers can hold greige fabric (undyed, woven or knitted loomstate fabric) and dye it as needed to respond to changing fashion styles and colour trends. This is the most commonly used stage as it enables just-in time processing
what does griege/loomstate mean?
terms used for a fabric in it’s natural state as it comes from the loom or knitting machine
what is garment dyeing?
finished garments can be dyed. A colour can be chosen at this very last stage, enabling retailers and manufacturers to react rapidly to market trends.
what is degradation?
The gradual breakdown of a dye, leading to colour loss in a product
what are the 7 different ways colour in a fabric can degrade?
-washing
-bleaching
-dry cleaning
-perspiration
-toiletries and cosmetics
-light
-rubbing (crocking)
how can washing degrade colour in a fabric?
dye can ‘bleed’ from a fabric when wet
how can bleaching degrade colour in a fabric?
chlorine bleach can remove colour from most fabrics so dyes used in swimwear need to be resistant to chlorine
how can dry cleaning degrade colour in a fabric?
the solvents used can cause some dyes to fade
how can perspiration degrade colour in a fabric?
a reaction to acids in sweat causes colour loss in localised areas such as under the arms
how can toiletries and cosmetics degrade colour in a fabric?
chemicals used in deodorants and perfumes can cause discolouration
how can light degrade colour in a fabric?
dye degrades and fades if repeatedly exposed to strong, bright sun or artificial light
how can rubbing (crocking) degrade colour in a fabric?
abrasion can cause dye loss or colour transfer when dry, dyed fabric rubs against a lighter coloured fabric
how do manufacturers keep consumer demand in mind?
by dyeing fabric at the last stage possible and using just-in-time (JIT) stock control systems gives manufacturers the opportunity to respond quickly to changes in consumer demand
-piece fabrics can be kept in their greige state and dyed as needed
-simple-shaped garments can be manufactured and kept undyed then dyed to order
how are printed designs different to fabric dyeing?
- printed designs don’t fully penetrate through a fabric, giving it an identifiable right and wrong side
what are the main advantages of printing over dyeing?
-more colours can be used
-complicated designs can be produced
-is it better for the environment as less water is used
what are the three steps for preparing a fabric for printing?
- desizing
2.scouring
3.bleaching
what is the process of desizing?
-the removal of ‘size’- a water-soluble substance that inhibits the absorption of dye or print medium.
what is the process of scouring?
-the removal of natural or machine impurities such as greases and oils that act as a barrier to dye or print medium absorption
what is the process of bleaching?
making the fabric evenly white before colour is added. synthetic fibres are naturally white so do not require bleaching
how is discharge dyeing done?
discharge paste is screen printed onto dyed fabric. the paste destroys the original dye to produce a pattern
what are the advantages of discharge dyeing?
-intricate patterns can be produced
-suitable for designs with large areas of background colour
-suitable for large print runs
what are the disadvantages of discharge dyeing?
-two production stages are involved
-discharge paste is expensive
how is block printing by hand done?
- a design is cut into a wooden block. printing paste is applied to the block. The block is pressed firmly onto the fabric leaving a repeating pattern
what are the advantages of block by hand printing?
-can be used on any fabrics and any fabric size
-sustainable process as blocks can be reused
-gives an ethnic craft aesthetic
what are the disadvantages of block by hand printing?
-time consuming
-expensive
-accurate positioning is essential
-a block is needed for each colour
-only suitable for small scale runs
how is stencil printing by hand done?
gaps are cut into acetate or card to create a pattern. the stencil is then positioned onto the fabric and printing paste is sponged or brushed through the cut areas.
what are the advantages of stencil printing by hand?
-stencils can be cut by hand or using a laser cutter
-stencils can be reused
-stencilled patterns can entirely cover or enhance small areas of fabrics
what are the disadvantages of stencil printing by hand?
-time consuming
-suitable for simple designs with limited colours
-stencils need to be used with care as the sections are connected with narrow ‘bridges’
how is rotary screen printing done?
-individual mesh rollers print one colour and part of the design in turn-the rollers rotate as the fabric travels below on a conveyor belt. an internal squeegee forces printing paste through open mesh areas onto the fabric
what are the rollers in rotary screen printing made from?
by hand using stainless steel mesh or photochemically on woven nylon
what are the advantages of rotary screen printing?
-it is the most commercially viable way of printing large quantities of fabric
-suited to designs that have pattern repeats
-can produce complex designs with five or more colours
-CAD is used to prepare the screens
-knitted fabrics can be printed on as this doesn’t stretch the fabric
what are the disadvantages of rotary screen printing?
-long set up time
-not suitable for JIT manufacturing
-the circumference of the rollers dictates the length of the pattern repeat
-only suitable for high-volume print runs
-the initial investment cost for machinery is high
how is flat bed screen printing done?
screens are mesh fabric stretched over frames. photochemicals create the design on each screen. a conveyor belt moves and stops the fabric. The screens are lowered, automatic squeegees push printing paste through ‘open’ areas of the screens. the screens are raised and the fabric moves on to receive another colour
what are the advantages of flatbed screen printing?
-accurate and relatively fast
-used for high volume print runs
-good for small-width fabrics
-can be used on a wider range of fabrics as the number of squeegee passes can be increased
-investment cost is lower than rotary screen printing machines
what are the disadvantages of flatbed screen printing?
-slower than rotary screen printing
-takes up more factory floor space
-not suitable for JIT production
-not cost-effective for small orders
-better suited to designs with few colours
how is transfer/sublimation printing done?
CAD generates the design. Long rolls of sublimation paper and inks are used to print the design. the printed paper and white fabric are held together in a heat press. High temperatures cause the printed dyes to turn into vapour, transfer and bond with the fabric.
what are the advantages of transfer/sublimation printing?
-quick set up and turnaround time reduces costs
-no colour or design constraints
-colour adjustments can easily be made using CAD
-good colour fastness as the dye bonds with the fabric
-fabric retains a soft handle
what are the disadvantages of transfer/sublimation printing?
-only effective on fabrics with 50% or more synthetic fibre content
-slower than screen printing methods
-slightly creased fabric ruins the transfer print
-a range of processes are required to set up a print run
how is digital printing done?
CAD generates the design. The pattern is sent to an ink jet printer fitted with direct dye printing cartridges. The pattern is printed onto the fabric or simple garment.
what are the advantages of digital printing?
-no colour or design constraints
-colour changes are quick to do
-patterns do not have to repeat
-works on most fabrics
-suitable for JIT production
-rapid turnaround of samples
-no minimum print run
what are the disadvantages of digital printing?
-expensive
-suitable for small print runs
-the size of the printer and printable area determines the width of the fabric that can be used
what must you consider before dyeing?
- sustainability
- colours- trends, meanings etc
3.fitness for purpose- it’s fastness to bleaching, perspiration etc - The type of dye to use- acid, direct, disperse
- whether you want to use computer systems
what can computer systems do for dyeing?
- reduces faults/flaws
- increased accuracy + consistency
- reduced costs (labour)
- time efficient
- can create dye for small or large scale dye runs + printing
What are the three types of hand printing methods?
-block printing
-stenciling
-screen printing
what are the key differences between modern printing methods and hand printing methods?
-hand printing methods are a lot less efficient and are labour intensive- meaning it is usually a lot more expensive
-hand printing methods are limited to a couple of colours- particularly if you are using block printing
-modern printing methods can use CAD which reduces labour costs and human error
-hand printing methods are only suitable for small scale production runs whilst modern printing methods can be suitable for large scale production
-hand printing methods are more likely to have human error mistakes
-complex designs can be created using CAD with multiple different colours
-modern printing methods support consumer demand- allows for quick editing of designs to meet consumer demands
