1.5 Enhancement of Materials Flashcards
What are the 3 stages of the process of dyeing?
- Immersing fabric in soluble dyestuff
- Dye attaches itself to fabric through absorption or a reaction with fibres
- Fix the dye so that the colour remains fast in the fabric
How is dyeing on large scales done?
In dye baths called vats
How is vat dyeing done?
- Vats filled with dye liquor and fabric dyed in batches
- Fabric agitated in vat to ensure an even dye penetration
- Excess dyed removed and fabric is washed with detergents and dyed
- Washing helps avoid later colour loss
What does discharge dyeing do?
Removes colour from a dyed fabric using a colour destroying deactivator that bleaches out white or light laggers in the darker coloured background
What does resist dyeing do?
Creates patterns by preventing colour from going into certain areas
What is tie-dye?
Wrapped, folded and tied areas on a fabric make it difficult for the dye to be absorbed there. Multi coloured patterns can be achieved if the fabric is untied and retied and then dyed with new colours
What is batik?
Melted wax or paste is hand painted onto fabric using a tjanting tool or brush. Once dried the painted areas prevent dye from going into the fabric
When is dye applied?
At all different stages in the processing of textiles
What is dope or spin dyeing?
Man made fibres are coloured before fibre extrusion. The dye is added to the spinning solution making it part of the fibre. This 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 yarns
What is yarn dyeing?
Yarn is dyed before construction into woven or knitted fabrics. Dyed yarn enables the production of multi coloured, patterned fabrics. Dyeing at this early stage commits a manufactured to a fabric colour
What is price or fabric dyeing?
Manufacturers can hold grieve fabric and dye it as needed to respond to changing fashion styles and colour trends. This is the most commonly used stage as if enables JIT processing
What is garment dyeing?
Finished fashion garments can be dyed. A colour can be chosen at this very last stage, enabling retailers and manufacturers to react rapidly to market trends
When is fabric considered colourfast?
If the dyes do not degrade, for example by fading, crocking or bleeding when washed or used
What do fabrics need dye fastness for?
- Washing
- Bleaching
- Dry cleaning
- Perspiration
- Toileteries and cosmetics
- Light
- Rubbing
What can washing cause?
Dye can ‘bleed’ from fabric when wet
What can bleaching cause?
Remove colour from most fabrics so dyes used in swimwear need to be resistant to chlorine
What can dry cleaning cause?
The solvents used can cause some dyes to fade
What can perspiration cause?
A reaction to acids in sweat causes colour loss in localised areas such as under the arms
What can toiletries and cosmetics cause?
Chemicals used in deodorants and perfumes can cause discolouration
What can light cause?
Dye degrades and fades if repeatedly exposed to strong, bright sun or artificial light
What can rubbing cause?
Abrasion can cause dye loss or colour transfer when they dry, dyed fabric rubs against a lighter coloured fabric
What do colour forecasters do?
Analyse sales figures and consumer interest to predict seasonal colour trends
What do dye companies do?
Buy trend information so they can supply th demand for new colours up to two years in advance of a retail season
What allows manufactures to make quick changes due to consumer demand?
Dyeing fabric at the last stage possible using JIT stock control systems
What does JIT production do?
Makes products as need; it is cost effective and better for the environment as there is less waste
How is printing designs different from dyeing?
Printed designs do not fully penetrate through a fabric so there is an identifiable right and wrong side
What are the advantages of printing over dyeing?
- More colours can be used
- Complicated designs can be produced
- Better for environment as less water is used
What finishes processes does fabric need to go through before printing?
- Desizing
- Scouring
- Bleaching
What is desizing?
The removal of ‘size’, a water soluble substance that inhibits the absorption of dye or print medium. Size is applied to warp yarns to strengthen the for the weaving process
What is scouring?
The removal of natural or machine impurities such as grease and oils that act as a barrier to dye or print medium absorption
What is bleaching?
Making the fabric evenly white before colour is added. Synthetic fibres are naturally white so do not require bleaching
What does digital printing do?
Prints a design directly onto the fabric
What is discharge printing?
- Discharge paste is screen printed onto dyed fabric
- Paste destroys the original dye to produce the pattern
What are the advantages of discharge printing?
- Intricate patterns can be reproduced
- Suitable for designs with large areas of background colour
- Suitable for large print runs
What are the disadvantages of discharge printing?
- Two production stages are involved
- Discharge paste is expensive
What is block printing by hand?
- A design is cut in relief on a wooden block
- Printing paste applied to the block
- Block pressed firmly onto fabric leaving a repeating pattern
What are the advantages of block printing by hand?
- Can be used on any fabrics and fabric sizes
- Suitable as all processes are traditionally done by hand
- Blocks can be reused
- Gives an ethnic craft aesthetic
What are the disadvantages of block printing by hand?
- Time consuming and expensive
- Accuate positioning essential
- Block needed for each colour
- Only suitable for small scale runs
What is stencil printing by hand?
- Gaps cut into acetate or card to create a pattern
- Stencil positioned on the fabric
- Printing paste is sponged or brushed through the cut areas
What are the advantages of stencil printing by hand?
- Stencils cut by hand or laser cutting
- Stencils can be reused
- Stencilled patterns can entirely cover or enhance small areas of fabrics
What are the disadvantages of stencil printing by hand?
- Suitable only for simple designs with limited colours
- Stencils need to be used with care as the sections are connected only with narrow ‘bridges’
What is rotary screen printing?
- Individual mesh rollers print one colour and part of the repeat design in turn
- Designs must fit the rollers seamlessly
- Rollers rotate as the fabric travels below on a conveyer belt
What are the advantages of rotary screen printing?
- Most commercially viable way of printing large quantities of fabric
- Suited to pattern repeats
- Produce complex designs
- CAD is used to prepare screens
- Knitted fabric printed
What are the disadvantages of rotary screen printing?
- Long set up time
- Not suitable for JIT manufacturing
- Circumference of rollers dictate the length of the pattern repeat
- Only suitable for high volume print runs
- Initak investment cost is high
What is flatbed screen printing?
- Conveyer belt moves and stops fabric
- Screens lowered, automatic squeegees push printing paste through open areas of the screen
What are the advantages of flatbed screen printing?
- Accurate and relatively fast
- Used for high volume print runs
- Good for small width fabrics
- Print large designs
- Used on wide range of fabrics
- Investment cost lower
What are the disadvantages of flatbed screen printing?
- Semi continuous
- 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
What is transfer printing?
- CAD generates design
- Printed paper and white fabric held together in a heat press
- High temperature causes the printed dyes to turn into vapour, transfer and bond with the fabric
What are the advantages of transfer printing?
- Quick set up and turnaround time reduces cost
- No colour or design constraints
- Colour adjustments easily made using CAD
- Good colour fastness
- Fabric retains soft handle
What are the disadvantages of transfer printing?
- Only effective on fabrics with 50% or more synthetic fibre content
- Slower than screen printing
- Slightly creased fabric ruins print
- Range of processes required
What is digital printing?
- CAD generates the design
- Pattern sent to an ink jet printer fitted with direct dye printing cartridges
- Pattern printed onto fabric or simple garment
What are the advantages of digital printing?
- No colour or design constraints
- Colour changes 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
- Size of the printer and printable area determines the width of the fabric that can be used
What does embroidery do?
Add colour, texture and pattern to a fabric. Stitch variations can be combined for decorative effect and decorative components can also be stitched into a design
How is hand embroidery done?
- Thread comes in a range of thicknesses and needs to be used with the correct size and type of needle
- Embroidery frames help to hold the fabric taut and in place
What are the 4 types of hand embroidery stitches?
- Flat stitches
- Linked stitches
- Looped stitches
- Knotted stitches
What are most sewing machines programmed with?
Decorative stitches that can be selected by changing the stitch pattern, length and width dials
What do computerised embroidery machines do?
Sew pre programmed designs. They come with software that allows users to create their own embroidery designs
What needs to be used for free machine embroidery?
- Attachment of a special sewing machine foot
- Specialist threads such as Madeira
- Lightweight fabrics supported with interfacing
What does quilting add?
Warmth, structure, pattern and texture to a fabric
What does english quilting make?
A thick decorative fabric that offers a wearer some protection but more importantly traps air and acts as an insulator
What does english quilting involve?
Placing a layer of wadding between two layers of fabric and then studying through the layers using a sewing machine quilting foot
What is italian and trapunto quilting?
Decorative techniques that produce a design in relief. Both techniques use two layers of fabric
What happens in italian quilting?
Cord is inserted between parallel lines of stitching to create a design
What happens in trapunto quilting?
Padding is inserted through slits on the underside of small enclosed stitches areas and then sewn up
