1.5 - Enhancing materials

P1 - Technical principles

dyestuff

an inorganic or organic coloured substance used to add colour to textile materials

surface decoration - dyeing

3 stages

• immerse barricade in soluble dyestuff

• dye attaches to fabric by absorption or a reaction with the fibres

• fixing dye so colour remains fast in fabric

dye liquor

a solution containing dyestuff, water and chemicals

• chemicals if needed to help dye bind to fibres

vat dyeing

dyeing on a large scale done in dye baths called vats

vat dyeing - process

• vats filled with dye liquor - fabric dyed in batches

• fabric agitated in vat to ensure penetration evenly

• excess dye removed

• fabric washed with detergent and dried

• helps to avoid later colour loss

discharge dyeing

removing colour from a dyed fabric using a colour destroying activator

• bleaches out light patterns on darker colour background

resist dyeing

creates pattern by printing colour from going on certain areas of a fabric

• e.g. tie dye, batik

resist dying - tie-dye

wrapped, folded and tied areas of a fabric make it hard for the dye to be absorbed there

• can make multi coloured patterns

• can untie, retie and dye different times with new colours

• cant replicate patterns exactly - products unique

resist dyeing - batik

melted wax or paste is hand painted onto fabric using a brush our a tjanting tool

• dried painted areas prevent dye entering fabric

• can submerge fabric in dye, or paint it one

• wax them removed

stages where dye can be applied

• dope dyeing

• stock dyeing

• yarn dyeing

• piece/fabric dyeing

• garment dyeing

dope dyeing

man made fibres are coloured before fibre extrusion

• dye added into spinning solution/dope

• makes it part of the fibre

• finished fibres have good light/wash fastness

stock dyeing

individual fibres dyed before they are spun into yarn

fibre extrusion

the process where fluid, molten and man made fibre polymer is pushed through holes in the nozzle of a spinning machine

• creates filament fibres

yarn dyeing

yarn is dyed before being woven/knitted into fabric

• can produce multicoloured, patterned fabrics

• e.g. stripes, checks, jacquard

• commits manufacturer to a fabric colour

piece/fabric dyeing

manufacturers can hold greige fabric and dye it as needed

• responds to changing fashion styles/colour trends

• most commonly used = allows JIT

garment dyeing

dyeing of finished garments

• can chose colour at this very last stage

• enables retailers and manufacturers to react rapidly to trends

Jacquard fabric

fabrics where a pattern is created through weaving or knitting rather than being printed on

greige/loomstate

when a fabric is in its natural state as it comes from the loom/knitting machine

• undyed

JIT - just-in-time

a stock control management system that ensures fabrics and components arrive at the factory just as they are needed to go onto the production line

dye degradation

the gradual breakdown of a dye

• leading to a loss of colour in a product

dye fastness

the ability of a fibre or fabric to retain dye

colourfast fabric

• if dyes don’t degrade

• need to have dye fastness to most factors

dye fastness factors - during care

• washing = fabric can bleed from wet fabric

• bleaching = can remove colour from most fabrics (so swimwear needs to be resistant to chlorine)

• dry cleaning = solvents can cause some dyes to fade

dye fastness factors - from wear

• perspiration = reaction to cid inset can cause colour loss in localised areas

• toiletries/cosmetics = chemicals in deodorant and perfume can cause discolouration

• light = strong sunlight or artificial light can degrade and fade dye

• rubbing/crocking = abrasion can cause dye loss, or colour transfer when dry dyed fabric rubs against a lighter fabric

dyeing - in response to seasonal colour trends

• colour forecasters = analyse sales figures and customer interest to predict trends

• dye companies = buy trend info so they can supply demand for new colours (2 years in advance of retail)

• trade fairs = show new colour trends e.g. première vision

dyeing - in response to customer demand

• dyeing at last stage using JIT stock control = manufacturers the opportunity to respond quickly to changes in demand

• JIT production makes products as needed - cost effective and less wasteful

• piece fabrics = kept in greige state and dyed as needed

• simple shaped garment = manufactured and kept undyed

printing - differences from dyeing

• prints don’t fully penetrate fabric = right and wrong side

• printing medium = dye and thickener to increase viscosity

• heat processes = most common method of permanently fixing dye to printed fabric

printing - benefits

• can use more colours

• can produce complicated designs

• better for environment - less water is used

processes to prepare fabric for printing

prepares loomstate fabric

• desizing

• scouring

• bleaching

desizing

the removal of size, a water soluble substance that prohibits printing medium absorption

• size applied to warp yarns to strengthen them for weaving

scouring

the removal of natural or machine impurities such as greases and oil

• act as a barrier to dye/print medium absorption

bleaching

making the fabric evenly white before colour is added

• not needed for naturally white synthetic fibres

direct printing

prints a design directly onto the fabric using various methods

direct printing - methods

• discharge printing

• block printing by hand

• stencil printing by hand

• rotary screen printing

• flatbed screen printing

• transfer/sublimation printing

• digital printing

discharge printing - method

discharge paste is screen printed onto dyed fabric

• destroys original dye to produce the pattern

discharge printing - advantages

• can produce intricate patterns

• suitable for designs with large areas of background colour

• suitable for large print runs

discharge printing - disadvantages

• discharge paste is expensive

• 2 production stages involved

block printing - method

deign cut in relief onto a wooden block

• printing paste applied to block

• block pressed onto fabric

• leaves a repeating pattern

block printing - advantages

• can be used on any fabric, any size

• sustainable - all processes by hand

• blocks can be reused

• ethnic craft aesthetic

block printing - disadvantages

• time consuming and expensive

• needs accurate positioning

• block needed for each colour

• only suitable for small scale runs

stencil printing - method

gas cut into acetate or card to create a pattern

• stencil positioned onto fabric

• printing paste sponged/brushed through cut areas

stencil printing - advantages

• stencils cut by hand or laser cutter

• can reuse stencils

• stencilled patterns can cover or enhance small areas of fabric

stencil printing - disadvantages

• similar to block printing

• only for simple designs with limited colours

• stencils need to be used with care

• sections only connected by narrow bridges

repeating pattern

the distance between one point of a designated and the exact point where it begins again

photochemically produced screens

screens mesh is coated with photosensitive chemicals

• areas meat to be printed are blocked off to stop them becoming insoluble when exposed to UV

• washing removes soluble chemicals from blocked areas

• print paste passes through mesh

rotary screen printing - method

individual mesh rollers print one colour and part of the repeat design in turn

• designs must fit the rollers seamlessly

• rollers made by hand using steel mesh or photochemically on nylon

• rollers rotate as the fabric travels down conveyor

• internal squeegee forces printing base through open mesh areas onto the fabric

rotary screen printing - advantages

• most commercially viable way to print large quantities of fabric

• suited to designs with pattern repeats

• can produce complex designs

• 5 or more colours

• CAD can prepare screens

• can print knitted fabrics = doesn’t stretch fabric

rotary screen printing - disadvantages

• long set up

• not suitable for JIT

• circumference of collars dictates length of pattern repeat

• only suitable for high volume print runs

• initial investment cost is high

flatbed screen printing - method

• screens = mesh fabric stretched over frames

• photochemicals create each part of the design open each screen

• conveyor belt moves and stops fabric

• screens lowered - squeegees push printing past through open areas of the screens

• screens raised - fabric moves forward to receive next colour

flatbed screen printing - advantages

• accurate and fast

• used for high volume print runs

• good for narrow fabrics

• large screens can print large designs

• can be used on a wider range of fabrics = number of squeegee passes can be increased

• lower investment cost

flatbed screen printing - disadvantages

• semi continuous, start stop operation

• slower than rotary printing

• takes up more factory space

• not suitable for JIT

• not cost effective for small orders

• better suited to designs with few colours

colour fastness

the ability of a fibre or fabric to retain dye fastness during manufacturing processes

• and when washed/exposed to light

dye sublimation printing

when heated pressure turns special dyes from a solid into a gas, then back into a solid

• turns into a solid when transferred from paper and bonded to synthetic fabric

dye sublimation printing - method

• CAD generates design

• long rolls of sublimation paper and ink used to print the design

• prints paper and white fabric held together in heat press

• high temp causes prints dye to turn to water vapour

• transfers and bonds with fabric

dye sublimation printing - advantages

• quick setup and turnaround - red. cost

• no colour/design constraints

• easily adjust colours with CAD

• good colour fastness

• design covers full width of fabric

• doesn’t need to repeat design

• fabric maintains soft handle

dye sublimation printing - disadvantages

• only works in 50% or more synthetic fibre fabrics

• slow than screen printing

• slight creases ruin the print

• range of processes needed to set up a print run

digital printing - method

• CAD generates design

• pattern sent to ink jet printer - fitted with direct dye cartridges

• pattern printed onto fabric or simple garment

digital printing - advantages

• no colour/design constraints

• colour changes quick to do

• patterns don’t have to repeat

• suitable for JIT

• rapid sample turnaround

• no minimum print run

digital printing - disadvantages

• expensive

• suitable for small print runs

• size of printable/printable area determines width of fabric that can be used

embroidery - effect

adds colour, texture and pattern to a fabric

• stitch variations can be combines

• gives decorative effect, can stitch in decorative components

hand embroidery

• thread comes in a range of thicknesses

• needs to be used with correct size/type of needle

• frames - hold fabric tight and in place

• can draw designs onto water soluble fabric to provide template

hand embroidery - stitches

• flat = e.g. running/satin stitch

• linked = e.g. chain stitch

• looped = e.g. blanket stitch

• knotted = e..g French knots

machine embroidery - pre programmed stitches

• most sewing machines are programmed with decorative stitches

• computerised machines have a larger range of decorative stitches

• can switch preprogrammed motifs, letters and numbers

• can only sew pre programmed designs

• come with software so users can create own designs

• attachable embroidery hoop holds fabric in tension and moves

feed dogs

the metal teeth-like ridges that move in and out of the metal plate below a sewing machines needle and presser foot

free machine embroidery

need a special sewing machine foot - allows drawing with stitches

• use specialist threads and support lightweight fabrics with interfacing

• hold fabrics taut in a hoop or flat on the base of the machine

• lower feed dogs for free motion

• move fabric around to allow stitches to build up in areas

• creates unique designs

quilting

adds warmth, structure, pattern and texture to a fabric

English quilting

makes a thick decorative fabric that offers the wearer some protection, traps air to act as an insulator

• place wadding between 2 layers of fabric

• stitch through layers using a sewing machine quilting foot

• fabrics should have grain line in same direction

• pin and tack layers together

• start in the middle and work outwards

Italian and trapunto quilting

decorative techniques that produce a design in relief

• uses 2 layers of fabric

• italian = cord inserted between parallel lines of stitching to create a design

• trapunto = padding inserted through slits on underside of small-enclosed stitched areas, then sewn up