DYES IN CHEMISTRY
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The process of dyeing involves the immersion of a fabric
in a solution of a dyestuff in water.
The first dye made was ‘Indigo’ but Blue dyes displaced
it because it was faster to light and washing.
The most important of the colorants are collectively
known as ‘Vat’ dyes.
The Fibre – Reactive dyes were designed for cellulose
It has 4 different components – Chromogen, Bridging
group, Fibre – Reactive group and Water Solublising
TYPES OF DYES
Natural Dyes – Indigo and madder – used in Japan and
Synthetic Dyes – In 1856, William Henry Perkin invented
these dyes in London from coal tar. The first synthetic dye
was Picric Acid.Today these dyes are used in the field of
textiles, Medicine, Chemistry, etc.
Mordant Dyes - These dyes can be applied only with a
mordant and are used for wool. Alizarin is an example.
Azo Dyes – These contain an azo group, -N=N- and are used
in foods and textiles. These dyes can give a complete rainbow
of colors. These dyes are very cheap to produce, are much
more stable in whole pH range, are heat stable and not
soluble in oils.
Vat Dyes – These dyes are obtained through oxidation, are
very bright and hold up better when bleached. These are
called ‘Vat Dyes’ because they are originally insoluble in
water, they undergo special preparation in large vats before
the cloth is introduced.
Hair and Food Dyes – Hair dyeing is achieved with a
synthetic dye applied with hydrogen peroxide that first
bleaches the natural pigment melanin. Dyes and synthetic
colorants are used in food. Many food dyes are banned
because they cause cancer.Food Additives are added in it.
Disperse Dyes – These are used for dyeing of cellulose
acetate,polysters,nylon and acrylic fibres.
Sulphur Dyes – These dyes are used to dye cotton with
dark colors. Sulphur Black 1 is the largest selling dye.
Direct Dyes – These dyes are used on cotton, paper,
leather,wool,silk and nylon and are used as pH indicators.
Digital Textile Printing
The process of directly printing
the textile dyes onto the pre
treated fabric is called Digital
It is far better than Traditional
Printing methods in terms of
flexibility, time, purposes,
applications and variety of
The Dye Inks which are
commonly used for this printing
are Acid dye inks, Reactive
dye inks and Disperse dye
These are Switchable
dye molecules for Non –
The chemical known as
Aniline consists of a
benzene ring substituting
on an ammonia molecule.
To make the dyes, the
manufacturers take aniline
and stick it with compounds
with alternating double and
single bonds. The idea is
that these compounds
extract the colors from
white light to appear red,
blue, etc. When these
compounds are exposed to
intense UV light, it breaks
apart the double bonds,
causing the color to
dissipate. That’s why
Aniline dyes get fade.
Chemistry Book of XII class.
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