knowledge about dyes

2. History
Earliest dyes used are of natural source.
Natural dyes are dyes or colorants derived
from plants, invertebrates, or minerals. The
majority of natural dyes are vegetable
dyes from plant sources—
roots, berries, bark, leaves, and wood—and
other organic sources such as fungi and lichens.

3. Cont…
• The ability of natural dyes to color textiles has
been known since ancient times. The earliest
written record of the use of natural dyes was
found in China dated 2600BC. Chemical tests
of red fabrics found in Egypt show the
presence of alizarin, a pigment extracted from
madder.
• Kermes (from the Kermes insect) is identified
in the bible book of Exodus

4. Cont…
• By the 4th century AD, dyes such as woad,
madder, weld, Brazilwood, and indigo and a
dark reddish-purple were known.
• Purple was made from a mollusk and clothing
made from it was so expensive only the royal
family could afford it.
• By the 15th century, dyes from insects, such as
cochineal and Kermes, were becoming more
common.

5. • By the 17th century, dyeing cloth "in the
wood" was introduced in England: logwood,
fustic, etc.
Problem Associated with natural dye
• Obtaining dye from natural source was a slow
inefficient wasteful and labour intensive
process.
• These are rarely pure compounds so
consistance is major issue.

6. • Reproducibility was a serious issue.
With the rise of dyestuff industry and day by day
increasing demand it was necessary to shift
towards the synthetic dye.
A great turn in the development of synthetic
dyes is the advancement in organic chemisty.

7. Pre Perkin Era
• In term of color, the yellow dyes comprised
the largest group of the natural dyes derived
from vegetable.
• Less impotent than black, blue, red.
• Red natural dyes were derived from insects
( Kermes, cochineal and Lac)
• Most impotant red dye was Madder also
known as AliZarin)

8. • Natural purple and dye was Tyrian purple
named on city of Tyre.
• The only Blue natural dyes were Indigo &
Woad
Only widely used natural dye still today is Indigo
though it is now produced synthetically.

9. Perkins Era
• 19th century was the revolution of dyestuff
industry.
• Wilhelm Hofmann study the coal tar products
that transformed the world of dye-making
• Hofmann and others prepared aniline and
other aromatic amino compound from the
coal tar hydrocarbon benzene, such as
toluene, naphthalene and anthracene.

10. Cont…
• After following the introductory course, Perkin
was assigned a research project related to coal
tar compounds. This was the
preparation of an amino derivative of
anthracene. Though the project was a failure,
Perkin’s interest in aromatic amino
compounds led to similar experiments with
benzene and naphthalene in 1855-56. Among
the products were colored substances.

11. Cont…
Mauveine is a mixture of four
related aromatic compounds differing in number
and placement of methyl groups. Its organic
synthesisinvolves dissolving aniline, p-toluidine,
and o-toluidine in sulfuric acid and water in a
roughly 1:1:2 ratio, then adding potassium
dichromate
Dye character of colorant was studied and find
suitable for dyeing of silk & wool.

12. Cont…
Perkin success attracts many chemist in this
direction and leads to revolutionary discovery in
field of dyestuff.

13. Classification of Dyes
Dyes can be classified by in many different ways.
1-Based of fiber types
Dyes for polyester, for cotton, for nylon etc.
2-Based of application
Direct dye, reactive dye, disperse dye etc.
3-Based of area of use (Paper, textile leather)
4-Organic & In-organic
5-Natural or synthetic
6-Based of chemical structure

14. Cont…
Theoretically there are four division of dyes.
• Donor-Acceptor Chromogens (Azo structure)
• Cyanine Chromogens (Natural dyes.)
• Polyene Chromogens (12 carbon conjugate
system)
• n-₳ chromogens (rarely exit in dyes)

15. Advantages of chemical Classification
• It identifies dyes as belonging to a group
which have specific characteristic.
• Manageable no of groups.
• This division is equally suitable for both textile
technologist and Chemist.
• Colour index is already classified based on this
system.

16. Chemical Classification of types
• Azo Dyes
• Anthraquinone Dyes
• Vat Dye
• Indigo Dyes
• Nitro Dyes
• Sulpher Dyes
• Phthalocyalines Dyes
• Aryl Carbonium Dyes (Di/Tri)

17. Cont…