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