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.
