DYE

DYE
- is a colored substance that has an affinity to the substrate to which it is being applied.
- Is a colored chemical substance that imparts color when applied to a substrate
- is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye
on the fiber.
NOTE: Both dyes and pigments appear to be colored because they absorb some wavelengths of light more
than others. In contrast with a dye, a pigment generally is insoluble, and has no affinity for the substrate. Some
dyes can be precipitated with an inert salt to produce a lake pigment, and based on the salt used they could be
aluminum lake, calcium lake or barium lake pigments.

HISTORY:
Dyed flax fibers have been found in the Republic of Georgia dated back in a prehistoric cave to
36,000 BP. Archaeological evidence shows that, particularly in India and Phoenicia, dyeing has been widely
carried out for over 5,000 years.

Sources of Dyes:
1. animal
2. vegetable
3. mineral
4. plants – greatest source (roots, berries, bark, leaves and wood)

Kinds of Dyes:
1. Natural Dyes
The majority of natural dyes are from plant sources – roots, berries, bark, leaves, and wood , fungi,
and lichens. Textile dyeing dates back to the Neolithic period.
Throughout history, people have dyed their textiles using common, locally available materials. Scarce
dyestuffs that produced brilliant and permanent colors such as the natural invertebrate dyes Tyrian purple and
crimson kermes were highly prized luxury items in the ancient and medieval world.
Plant-based dyes such as woad, indigo, saffron, and madder were raised commercially and were
important trade goods in the economies of Asia and Europe. Across Asia and Africa, patterned fabrics were
produced using resist dyeing techniques to control the absorption of color in piece-dyed cloth. Dyes from
the New World such as cochineal and logwood were brought to Europe by the Spanish treasure fleets, and the
dyestuffs of Europe were carried by colonists to America

2. Synthetic Dyes –
The first human-made organic dye, mauveine or aniline, was discovered serendipitously by William
Henry Perkin in 1856, the result of a failed attempt at the total synthesis of quinine. Many thousands of
synthetic dyes have since been prepared.
Synthetic dyes quickly replaced the traditional natural dyes. They cost less, they offered a vast range of
new colors, and they imparted better properties to the dyed materials.

PROPERTIES OF DYES
The properties of dyes are based on the following factors:
1. Shade (brightness or dullness) 3. Level Dyeing Properties 5. Dusting
2. Fastness Requirements 4. Ease of Application 6. Environmental Concerns

Important properties that are considered when selecting a dye for use:
1. Ease of application 2. durability of color 3. resistance to sunlight and chemicals

A good dye has the following qualities:

1. It has a suitable color.
2. It fixes itself to fabrics.
3. It has fastness properties, such as: Fastness to light, Resistance to the action of water, diluted acids, alkalis,
and various organic solvents used in dry cleaning.

TYPES OF DYES
A. According to how they are used in the dyeing process:
1. Acid dyes
- are water-soluble anionic dyes that are applied to fibers such as silk, wool, nylon and modified acrylic
fibers using neutral to acid dye baths.
 - Attachment to the fiber is attributed, at least partly, to salt formation between anionic groups in the
dyes and cationic groups in the fiber.
-Acid dyes are not substantive to cellulosic fibers.
- Most synthetic food colors fall in this category.
2. Basic dyes
- are water-soluble cationic dyes that are mainly applied to acrylic fibers, but find some use for wool
and silk.
- acetic acid is added to the dye bath to help the uptake of the dye onto the fiber.
- are also used in the coloration of paper.

3. Direct or substantive dyeing

- is normally carried out in a neutral or slightly alkaline dyebath, at or near boiling point, with the
addition of either sodium chloride (NaCl) or sodium sulfate (Na2SO4) or sodium carbonate (Na2CO3).
- are used on cotton, paper, leather, wool, silk and nylon.
- used as pH indicators and as biological stains.

4. Mordant dyes
- require a mordant, which improves the fastness of the dye against water, light and perspiration. - -
- different mordants can change the final color significantly.
- Most natural dyes are mordant dyes
- the synthetic mordant dyes, or chrome dyes, used for wool; these comprise some 30% of dyes used
for wool, and are especially useful for black and navy shades.
- The mordant,potassium dichromate, is applied as an after-treatment.
Note: It is important to note that many mordants, particularly those in the heavy metal category, can be
hazardous to health and extreme care must be taken in using them.

5. Vat dyes
- are essentially insoluble in water and incapable of dyeing fibres directly.
- reduction in alkaline liquor produces the water soluble alkali metal salt of the dye and has an affinity
for the textile fibre. Subsequent oxidation reforms the original insoluble dye.
- The color of denim is due to indigo, the original vat dye.

6. Reactive dyes
- utilize a chromophore attached to a substituent that is capable of directly reacting with the fibre
substrate.
- The covalentbonds that attach reactive dye to natural fibers make them among the most permanent
of dyes.
- "Cold" reactive dyes, such as Procion MX, Cibacron F, and Drimarene K, are very easy to use because
the dye can be applied at room temperature.
-is the best choice for dyeing cotton and other cellulose fibers at home or in the art studio.

7. Disperse dyes
- were originally developed for the dyeing of cellulose acetate, and are water insoluble.
- The dyes are finely ground in the presence of a dispersing agent and sold as a paste, or spray-dried
and sold as a powder.
- main use is to dye polyester but they can also be used to dye nylon, cellulose triacetate, and acrylic
fibres.
- a dyeing temperature of 130 °C (266 °F) is required, and a pressurized dye bath is used. The very fine
particle size gives a large surface area that aids dissolution to allow uptake by the fibre.
- The dyeing rate can be significantly influenced by the choice of dispersing agent used during the
grinding.

8. Azoic dyeing
- is a technique in which an insoluble azo dye is produced directly onto or within the fibre.
- This is achieved by treating a fibre with both diazoic and couplingcomponents. With suitable
adjustment of dyebath conditions the two components react to produce the required insoluble azo dye.
- This technique of dyeing is unique, in that the final color is controlled by the choice of the diazoic and
coupling components.
- This method of dyeing cotton is declining in importance due to the toxic nature of the chemicals
used.
9. Sulfur dyes
- are two part "developed" dyes used to dye cotton with dark colors.
 - The initial bath imparts a yellow or pale chartreuse color.
- This is after treated with a sulfur compound in place to produce the dark black we are familiar with in
socks for instance.
- Sulfur Black 1 is the largest selling dye by volume.
Food dyes
- are classed as food additives, they are manufactured to a higher standard than some industrial dyes.
- can be direct, mordant and vat dyes, and their use is strictly controlled by legislation.

Other important dye

A number of other classes have also been established, including:
1. Oxidation bases - for mainly hair and fur
2. Laser dyes: - rhodamine 6G and coumarin dyes.
3. Leather dyes - for leather
4. Fluorescent brighteners- for textile fibres and paper
5. Solvent dyes- for wood staining and producing colored lacquers, solvent inks, coloring oils, waxes.
6. Carbene dyes- a recently developed method for coloring multiple substrates
7. Contrast dyes - injected for magnetic resonance imaging, are essentially the same as clothing dye except
they are coupled to an agent that has strong paramagnetic properties.
8. Mayhem's dye- used in water cooling for looks, often rebranded RIT dye

Dyeing Process
- process of coloring fibers, yarns, or fabrics with either natural or synthetic dyes
- is an ancient art which predates written records. It was practiced during the Bronze age in Europe.
Primitive dyeing techniques
- included sticking plants to fabric or rubbing crushed pigments into cloth. The methods became more
sophisticated with time and techniques using natural dyes from crushed fruits, berries and other plants, which
were boiled into the fabric and gave light and water fastness (resistance), were developed.
Dyeing can be done at any stage of the manufacturing of textile- fiber, yarn, fabric or a finished textile
product including garments and apparels. The property of color fastness depends upon two factors- selection
of proper dye according to the textile material to be dyed and selection of the method for dyeing the fiber,
yarn or fabric

COMMON DYES:
1. Indigo dye
- is an organic compound with a distinctive blue color
- Historically, indigo was a natural dye extracted from plants, and this process was
important economically because blue dyes were once rare.
- is among the oldest dyes to be used for textile dyeing and printing
- Nearly all indigo dye produced today – several thousand tons each year – is synthetic. It is the blue
of blue jeans.

Production of Indigo dye in a BASF plant (1890)

In 1897, 19,000 tons of indigo were produced from plant sources. Largely due to advances in organic
chemistry, production by natural sources dropped to 1,000 tons by 1914 and continued to contract. These
advances can be traced to 1865 when the German chemist Adolf von Baeyer began working on the synthesis of
indigo. He described his first synthesis of indigo in 1878 (from isatin) and a second synthesis in 1880 (from 2-
nitrobenzaldehyde). The synthesis of indigo remained impractical, so the search for alternative starting
materials at BASF and Hoechst continued. The synthesis of N-(2-carboxyphenyl)glycine from the easy to
obtain aniline provided a new and economically attractive route. BASF developed a commercially feasible
manufacturing process that was in use by 1897. In 2002, 17,000 tons of synthetic indigo were produced
worldwide.

Uses of Indigo Dye

1. Primary use : dye for cotton yarn, which is mainly for the production of denim
cloth for blue jeans.
On average, a pair of blue jean trousers requires 3–12 g of indigo. Small
amounts are used for dyeing wool and silk.
2. Indigo carmine, or indigotine, is an indigo derivative which is also used as a
colorant. FD&C Blue No. 2.
Chemical properties
Indigo is a dark blue crystalline powder that sublimes at 390–392°C. It is insoluble in water, alcohol,
orether, but soluble in DMSO, chloroform, nitrobenzene, and concentrated sulfuric acid. The chemical
formula of indigo is C16H10N2O2.
The molecule absorbs light in the orange part of the spectrum (λmax = 613 nm).[11] The compound owes
its deep color to the conjugation of thedouble bonds, i.e. the double bonds within the molecule are adjacent
and the molecule is planar. In indigo white, the conjugation is interrupted because the molecule is nonplanar.

Chemical synthesis
Given its economic importance, indigo has been prepared by many methods. The Baeyer-Drewson
indigo synthesis dates back to 1882. It involves an aldol condensation of o-nitrobenzaldehyde with acetone,
followed by cyclization and oxidative dimerization to indigo.
Indigo derivatives
Structure of Tyrian purple
Tyrian purple is a dull purple dye that is secreted by a common Mediterranean snail.
It was highly prized in antiquity.

2. Methyl orange is a pH indicator frequently used in titrations because of Methyl orange (pH indicator)
its clear and distinct colour change. Because it changes colour at the pH of below pH 3.1 above pH 4.4
a midstrength acid, it is usually used in titrations for acids. Unlike
a universal indicator, methyl orange does not have a full spectrum of 3.1 ⇌ 4.4
colour change, but has a sharper end point.
3. Aniline Yellow is a yellow azo dye and an aromatic amine. It is a derivate of azobenzene. It has the
appearance of an orange powder. Aniline Yellow was the first azo dye. It was first produced in 1861 by C.
Mene. The second azo dye was Bismarck Brown in 1863. Aniline Yellow was commercialized in 1864 as the first
commercial azo dye, a year after Aniline Black. It is manufactured from aniline.
Uses of Aniline
Aniline Yellow is used in microscopy for vital staining, in pyrotechnics for
yellow colored smokes, in yellow pigments and inks including inks for inkjet printers. It is
also used in insecticides, lacquers, varnishes, waxes, oil stains, and styrene resins. It is also
an intermediate in synthesis of other dyes, e.g. chrysoidine, indulines, Solid Yellow,
and Acid Yellow.

4. Alizarin or 1,2-dihydroxyanthraquinone (also known as Mordant Red 11 and Turkey Red -is an organic
compound with formula C14H8O 4 that has been used throughout history as a prominent red dye, principally
for dyeing textile fabrics. Historically it was derived from the roots of plants of the madder genus
In 1869, it became the first natural pigment to be duplicated synthetically.[3]
- is the main ingredient for the manufacture of the madder lake pigments known to painters as Rose
madder and Alizarin crimson. Alizarin in the most common usage of the term has a deep red color, but the
term is also part of the name for several related non-red dyes, such as Alizarine Cyanine Green and Alizarine
Brilliant Blue.

Structure and properties

Alizarin is one of ten dihydroxyanthraquinone isomers. Its molecular structure can be viewed as being
derived from anthraquinone by replacement of two neighboring hydrogen atoms (H) by hydroxyl groups (-OH).
It is soluble in hexane and chloroform, and can be obtained from the latter as red-purple crystals, m.p. 277–
278 °C. Alizarin changes color depending on the pH of the solution it is in, thereby making it a pH indicator.

USES OF ALIZARIN
Alizarin Red is used in a biochemical assay to determine, quantitatively by colorimetry, the
presence of calcific deposition by cells of an osteogenic lineage. As such it is an early stage
marker (days 10–16 of in vitro culture) of matrix mineralization, a crucial step towards the
formation of calcified extracellular matrix associated with true bone stem cells.

5. Malachite green is an organic compound that is used as a dyestuff and has emerged as a controversial
agent in aquaculture. Malachite green is traditionally used as a dye for materials such as silk, leather,
and paper. Although called malachite green, the compound is not related to the mineral malachite — the
name just comes from the similarity of color.
Structures and properties
Malachite green is classified in the dyestuff industry as a triarylmethane dye and also using in pigment
industry. Formally, Malachite green refers to the chloride salt [C6H5C(C6H4N(CH3)2)2]Cl, although the term
Malachite green is used loosely and often just refers to the colored cation. The oxalate salt is also marketed.
The chloride and oxalate anions have no effect on the color. The intense green color of the cation results from
a strong absorption band at 621 nm (extinction coefficient of 105 M−1cm−1).

Malachite green is prepared by the condensation of benzaldehydeand dimethylaniline to give leuco malachite
green (LMG): C6H5CHO + 2 C6H5N(CH3)2 → C6H5CH(C6H4N(CH3)2)2 + H2O
Second, this colorless leuco compound, a relative oftriphenylmethane, is oxidized to the cation that is MG:
C6H5CH(C6H4N(CH3)2)2 + HCl + 1/2 O2 → [C6H5C(C6H4N(CH3)2)2]Cl + H2O
Preparation
Malachite green was first prepared by Fischer in 1877 by condensing benzaldehyde and dimethylaniline in the
molecular ratio 1:2 and in the presence of a dehydrating agent.

Uses of Malachite green

- is traditionally used as a dye. Millions of kilograms of MG and related triarylmethane dyes are
produced annually for this purpose.
MG is active against the oomycete Saprolegnia, which infects fish eggs in
commercial aquaculture, and other fungi. Furthermore, MG is also used as
a parasiticide andantibacterial.[4] It is a very popular treatment
against ichthyophthirius in freshwater aquaria. The principal metabolite, LMG, is found in
fish treated with malachite green, and this finding is the basis of controversy and government regulation. See
also Antimicrobials in aquaculture.
MG has frequently been used to catch thieves and pilferers. The bait, usually money, is sprinkled with
the anhydrous powder. Anyone handling the contaminated bait will find that on washing the hands, the
contact with water will provoke an indelible green stain on the skin lasting for several days.

IMPORTANCE OF DYES
The study of dyes made organic chemistry popular and is even lead to the invention of drugs based on
the chemical intermediates of dyes, like the invention of aspirin and sulfonamides.
Research in dyes is also responsible for colour photography as we know it. In 1873 the German photo
chemist Hermann Wilhelm Vogel added dyes to film that was only sensitive to blue and UV light, allowing the
film to capture the colour green.
By 1907 the French Lumiere brothers had perfected a colour process for the public called
Autochrome. Today dyes are also widely used in printing, where the colours of cyan, yellow, magenta and
black combine to form all the colours visuals that you see printed.

Dyes - are substances that add color to textiles. They are incorporated into the fiber by chemical reaction,
absorption, or dispersion. Dyes differ in their resistance to sunlight, perspiration, washing, gas, alkalis, and
other agents; their affinity for different fibers; their reaction to cleaning agents and methods; and their
solubility and method of application.
Fiber Reactive Dyes:
- are the absolute best type of dyes made for fabrics or fibers made from plant materials. Plant
materials means anything made from a plant including; Cotton, Linen, Rayon, Hemp, Bamboo, Paper,
Jute, etc. The dyes also work well on silk.
- considered to be "cold water dyes" which in the world of dyes really means warm water, but the dyes
do not need to be heated to be used.
- are best for cottons or other plant materials because they are very color fast and wash fast. The dye
attaches itself to the fabric via a chemical reaction where the dye actually becomes part of the fabric.
Chemicals used in dyeing with reactive type dyes.
Direct application dyeing is a dyeing process where the dye is made in small concentrated batches. The dye is
then applied directly to the fabric. Squirted, painted, poured, or sponged on with various tools such as pipettes
(big plastic eyedropper type tools,) squeeze bottles, sponges, stamps, or paint brushes.
1. Dye Fixer - is a chemical called sodium carbonate. The fixer is needed to make these dyes work.
Fixer causes the important chemical reaction that makes these dyes become part of the fabric. In
direct application dyeing such as tie dyeing, the fabric is first soaked in a solution of dye fixer dissolved in
water. In vat dyeing, solid color dyeing, the dye fixer is added to the dye bath near the end of the dyeing
process
2. Urea- is used in tie dyeing or other direct application dyeing. It is generally not used in Vat (solid color)
dyeing. Urea helps large amounts of dye dissolve in small amounts of water. Urea helps the dye penetrate the
fabric. Moisture is an important component of the chemical reaction process with these dyes, and urea helps
draw moisture to the chemical reaction.
3. Ludigol - is used in tie dyeing or other direct application dyeing. It is generally not used in Vat dyeing. Once
reactive dye is mixed with water, it slowly starts to break down in the water. When this happens, over time the
dye becomes less effective.
Ludigol is added to the dye to keep the dye from reacting with, or breaking down in the water. It keeps
the dye fresher longer, and allows more dye to react with the fabric.
4. Water Softener: Dyes work better in soft water. Water softener is used in both tie dye and solid color
dyeing. One 8 ounce bag of water softener will tie dye approximately 160 shirts.
5. Sodium alginate - is used to thicken dye mixtures for hand painting and silk screening.
6. Synthrapol detergent - is used to wash out loose dye after the fabric is dyed
- is used to wash out different colored dyes, as in tie dyes and keep those dyes from staining other
parts of the fabric.