Dyes and Fibers Carol LeBaron Chemistry and Art February 15-17, 2004

1
Dyes and FibersCarol LeBaron Chemistry and
ArtFebruary 15-17, 2004
2
Nasca Wari textile, 400 CE Resist dyed
3
Light is made up of bands pf varying wavelengths
4
Reflection

• White can only be broken up by prisms or by
  colorants such as pigments and dyes
• This surface has no colorant so the light is
  reflected

5
It can be fully absorbed by the surface
6
Or a transparent surface may let all of the light
pass through or a colored surface may absorb part
of the spectrum
7
Bands of light mix together to produce lighter
colors
8
A blue surface absorbs red, orange, and yellow
light
9
A yellow surface absorbs blue and violet light
10
The pigment primaries absorb and reflect
different combinations of colored light
11
Interference the kind of surface light hits can
affect the way light waves behave
12
Structural Color

• Iridescence
• Luminescence
• Refraction
• Diffraction
• Fluorescence
• Phosphorescence

• Materials that light hits can cause a multitude
  of effects

13
The nature of fiber affects the way light appears
14
Fiber reflects, refracts, absorbs and diffuses
15
The unique color properties of fiber depend on
the interaction of fabric structure, dye
application, and light
Humidity (2002)
16
Pigments and Dyes

• A dye is a colorant that goes into solution or
  dissolves. Dye particles break apart into single
  molecules
• Pigment particles remain clustered together in
  suspension
• Dyes have a chemical affinity for fiber but
  pigments do not

Pigment particles
Dye molecules
17
Pigments and Dyes

• Pigment molecules carry their own color
• They do not unite with fiber molecules chemically
  and must be fixed to the fibers with bonding
  agents
• In man made fibers pigments can be mixed into the
  fiber solution before it is formed

• Dyes migrate out of the solution, are absorbed
  into the fiber, and diffuse from the surface of
  the fiber toward its center. There they either
• Bond chemically with fiber molecules
• OR
• React chemically with fiber molecules to produce
  permanent, enlarged colored fiber molecules
• Both situations are permanent

18
Dye molecules must be firmly fixed to fiber
Chain fiber molecule
Dye molecules
19
A negative dye molecule links with a positive
fiber molecule at a dye site. The process is
affected by surface charge, temperature, and
agitation. Different fibers have different
numbers of dye sites. Wool fiber has 1000 dye
sites, silk has 100, and cotton has less than 10
20
Assembly of dye molecules at the fiber surface

• When soaked in water all fibers acquire an
  electric potential or surface charge
• Cellulosic fibers acquire negative charges
• Protein fibers acquire both positive and negative
  charges, depending on the pH of the water
• Acid solutions help break down protein fibers to
  allow dye sites access to the dye
• Cellulose fibers must be soaked in alkaline
  solution
• Salt is used to set up electrical movement that
  initiates the movement of dye molecules in search
  of a resting place on the fiber

21
Once the dye molecule enters the fiber, it has a
a chemical reaction with it. It is enlarged,
which prevents its exit.
22
Color is produced when a divided molecule is
united.
23
Acid Dyes

• Used mainly on wool, silk, and nylon
• They have acid chemical groups in their dye
  molecules
• They use an acid dye bath to produce the chemical
  reaction
• Reaction involves acid, salt, heat, agitation,
  and time
• Amount of acid and rate at which it is added
  affects the rate at which the dye bonds
• Salt slows the bonding process, helping the dye
  color the fiber evenly. It attaches to the dye
  first.

24
Gradually, dye replaces the salt and bonds with
the fiber. Leveling is achieved when this
happens at an even rate.
25

• Heat affects the leveling of the dye bath by
  speeding up the chemical reaction
• Generally the dye bonds slowly until 160 F
• Agitation helps keep both chemicals and heat
  evenly distributed
• The full immersion time is necessary to allow the
  dye to be light fast and wash fast

26
Structural Orientation

• Structural orientation is the arrangement of
  parts relative to one another within a fiber
  piece
• Molecules in a fiber
• Fibers in a piece of yarn
• Yarn in a piece of fabric
• It affects moisture and dye absorption
• Textile polymers are chains with a monomer for
  each link
• Fiber polymers have the same structure that
  fibers do

27
Chromophores and auxochromes

• The ability of dye to create color comes from
  chromophores in the dye molecules
• Auxochromes regulate the intensity of color.
  They are chemical groups that make dyes water
  soluble. They also provide chemical groups that
  form bonds between the dye and fiber
• A dye bath must contain both chromophores and
  auxochromes, either from the dyestuff alone or a
  mixture of dye and other added chemicals

28
The structural orientation of the polymers within
a fiber varies, It affects dye resultsand other
fiber properties
29
Dye and molecular orientation

• Amorphous areas of a fiber take more dye than
  highly oriented areas
• They will be darker in the dye bath
• A fibers character depends on the color changes
  that take place from amorphous areas to
  crystalline or oriented areas
• All fibers contain all three areas in different
  degrees

30
Fibers

• Fiber molecules are arranged in fiber filaments
• Loose arrangement of fibers allows good
  penetration
• Fibers are often dyed before they are made into
  yarn for this reason
• Fibers are combed before they are made into yarn

Cotton fiber
31
Different fibers have different surfaces
32
Yarn staples
Lightly combed good penetration
Carded and combed fairly good penetration
Tightly packed poor penetration
33
The shape of the fiber filament affects
appearanceWool fibers are crimped and create an
absorbent surface
34
Structure of a wool fiber
35
The size of the yarn and the way it is plied will
affect the finished material
36
Weave structure affects color and appearance of
the dyed piece
37
Wool fiber comes in different colors from the
animal
38
Heat, agitation and moisture cause wool fiber to
felt wool fiber after it is felted
39
Wool fabric after fulling
After the fibers Have locked together
Before
40
Resist Dyeing
41
Two Examples of Clamp Resist with Folding
42
Chemistry Lab
43
Removing the Dyed Piece
44
Placing in the Rinse Tank
45
Larkspur