Unit - Chemistry of Fibres, Textiles and
The following links are to wikipedia for information on
traditional textile dyes.
Medieval dyers use long poles to stir cloth in the dye bath to
produce red cloth.
From the British Library, Royal Ms 15 E. III f.269 (1482) via
This lecture will attempt to summarise some of the topics covered
in a "Tutorial Review" of historical dyes published by Hamish
McNab (University of Edinburgh) in Chem.
Soc. Rev., 2004, 33, 329-336.
Throughout the world, natural dyes have been used since the most
ancient times until the end of 19th century when they were
largely replaced by cheaper synthetic dyes. The ancient dyestuffs
were generally organic materials obtained from plants, insects,
shellfish and lichens, whereas many of the earliest pigments were
inorganic materials obtained from natural ores.
Where did the earliest dyes come from? See the "Worst jobs in
history" Tudor era video clips that feature
4- indigo and
5- indigo continued
from woad (Isatis tinctoria) and Royal age
Tyrian purple from (Murex brandaris).
Initially the method we will use for classifying the dyes will be
based on their colour; blue, purple, red, yellow as well as by a
description of the chemical structure and identifying the
Most blue and purple colours were derivatives of indigo, obtained
either from woad or from the indigo plant, though some other
sources (e.g. shellfish and lichens) were used. Reds were often
anthraquinone derivatives obtained from plants or insects.
Yellows were almost always flavonoid derivatives obtained from a
variety of plant species. Most other colours were produced by
over-dyeing, e.g. greens were obtained by over-dyeing a blue with
a yellow dye.
Most of the naturally occurring indigo derivatives are insoluble
in water but may become soluble in the presence of reducing
agents. The fibres are therefore treated using a technique called
vat dyeing such that whilst the dye is in solution the fibre is
added to the dye bath and following its removal and exposure to
air the insoluble dye is trapped inside the fibre.
The natural products from which indigo is obtained include
indican (2a), which occurs in Indigofera species, e.g. the indigo
plant itself Indigofera
tinctoria L., as well as woad (Isatis
tinctoria L. which contains both indican (2a) and isatan
Irrespective of the starting plant source the dye extraction
follows the same process. The fermentation stage degrades the
glycosides by enzymatic hydrolysis to indoxyl (3) (a mixture of
keto-enol tautomers) which is then oxidised to 'leuco-indigo' (6)
and eventually to indigotin (1). A side reaction can occur if
indoxyl is converted by oxidation to the diketone, isatin (4)
that can then further react with another molecule of indoxyl (3)
to produce indirubin (5).
Preparation and UV/Vis spectrum of Indigotin (wavelength
The primary use for indigo today (several thousand tons each
year) is as a dye for cotton yarn, which is mainly for the
production of denim cloth for blue jeans. On average, a pair of
blue jeans requires 3 - 12 g of indigo. Small amounts are used
for dyeing wool and silk. All of the dye used is synthetically
carmine, or indigotine, is an indigo derivative (sodium salt
of 5,5'-indigodisulfonic acid) that is also used as a colorant.
Approximately 20M kilograms are annually produced, again mainly
for blue jeans. In addition it is used as a food colorant, and is
listed in the USA as FD&C Blue No. 2, and in the European
Union as E132.
Describe the processes that have been used for the commercial
synthesis of indigotin and indigo carmine.
The purple dyes obtained from shellfish are bromo-derivatives of
indigotin (1). Arguably, 6,6'-dibromoindigotin is the oldest
known pigment, the longest lasting, the subject of the first
chemical industry, the most expensive and the best known. See the
Review by Chris Cooksey in Molecules 6
(9),736-769 (2001). and a bibliographic
list of references related to Tyrian purple.
The three main species of molluscs used in the Mediterranean
region were spiny dye-murex (Bolinus
brandaris L. or Murex brandaris), rock-shell
(Thais haemastoma L. or Purpura haemastoma),
and banded dye-murex (Hexaplus trunculus L. or Murex
trunculus). As in the case of indigo plant sources, the dye
is not present in the live mollusc. It is generated by enzymatic
hydrolysis of precursors found in the animals' hypobranchial
glands, to provide derivatives of indoxyl (3) followed by
photochemical conversion to the purple pigment. Only very small
amounts of dye (often < 1 mg) can be obtained from each
mollusc (enough to dye only ca. 1 g of wool) making these dyes
very expensive commodities.
possible chromophore and crystal structure of 6,6'-dibromoindigotin
A comparison between the use of indigo or dibromoindigo as dyes
can be seen from the reflectance
spectra of wool samples. The absorption maximum of indigo
shifts from 605 nm in solution to over 650 nm as a dye, whereas
that of dibromoindigo shifts from 590 nm to 520 nm.
Reflectance spectra of wool samples dyed with dibromoindigo
(purple) and indigo (blue).
The main red insect dyes are from plant parasites belonging to
the Coccidea family and are extracted from American cochineal
(Dactylopius coccus Costa), kermes (Kermes
vermilio Planchon), Polish cochineal (Porphyrophora
polonica L.), Armenian cochineal (Porphyrophora
hamelii Brandt) and lac (Kerria lacca Kerr). The
chromophores in all of these scale insect dyes are derivatives of
In the case of cochineal the colourant (carminic acid) is
extracted from the bodies of female insects just prior to
egg-laying time and as such, may contain from 10 to 20% of their
dry weight of the dye. The collected insects are dried and
extracted with hot aqueous basic solution that may contain a
samll amount of ethanol. It has estimated that about 25 million
insects are required to make 14.5 kg of water-soluble
Red dyes and the structure of carminic acid
Plant anthraquinone reds
Logwood in Jamaica
campechianum (Logwood) was used for a long time as a natural
source of dye, and still remains an importance source of
haematoxylin, which is used in histology for staining. The bark
and leaves have found use in various medical applications. In its
time, logwood was considered a versatile dye, and was widely used
on textiles and for paper. The dye's colour depends on the
mordant used as well as the pH. Like litmus, it is red in acidic
environments and blue in alkaline ones.
echinata (Brazilwood) is a species of Brazilian timber tree
in the pea family, Fabaceae. Common names include Brazilwood,
Pau-Brasil, Pau de Pernambuco and Ibirapitanga (Tupi). This plant
has a dense, orange-red heartwood that takes a high shine, and it
is the premier wood used for making bows for stringed
instruments. The wood yields a red dye called brazilin, which
oxidizes to brazilein.
Simulation of C-NMR of B=Haematein
Flavonoids are the most important plant pigments for flower
colouration producing yellow or red/blue pigmentation in petals
designed to attract pollinator animals.
R'= H, R"=H apigenin; R'= H, R"=OH luteolin; R'= OH, R"=H
MS of luteolin and kaempferol
Although both luteolin
and kaemferol have the same RMM and show a peak at 287 they
can be readily distinguished by the intense peak at 165 for
kaempferol that comes about by the cleavage shown by the red
dotted line above. This leaves the left hand benzene ring intact
and is stabilised by the R' hydroxy group (not present in
The plant species Reseda
luteola was the most widely used source of the natural
dye known as weld. The plant is rich in luteolin, a flavonoid
which produces a bright yellow dye. The yellow could be mixed
with the indigo blue from woad (Isatis tinctoria) to produce
greens, such as Lincoln green.
The dye was in use by the first millennium BC, and perhaps
earlier than either woad or madder. Use of this dye came to an
end at the beginning of the twentieth century, when cheaper
synthetic yellow dyes came into use.
Saffron, turmeric and other yellows
obtained from the stigmatas of the flowers of Crocus
sativus L. and has a long history of use as a direct dye
dating back to Egyptian times. It was very popular in Persia in
Classical times. It was later replaced by cheaper dyes, like
weld, with better fastness properties. When used as a direct dye,
it gives a beautiful orange yellow colour and it can also be used
with alum mordant.
Saffron contains more than 150 volatile and aroma-yielding
compounds. In addition it has many nonvolatile active components,
many of which are carotenoids, including zeaxanthin, lycopene,
and various α- and β-carotenes. However, saffron's
golden yellow-orange colour is primarily the result of
α-crocin, a glucoside of crocetin, a polyunsaturated
Yellow dyes and the structure of crocin
(Curcuma longa) is a rhizomatous herbaceous perennial plant of
the ginger family, Zingiberaceae.
If the rhizomes are boiled for several hours and then dried in
hot ovens, They can then be ground into a deep orange-yellow
powder commonly used as a spice in curries and other South Asian
and Middle Eastern cuisine, for dyeing, and to impart color to
mustard condiments. Its active ingredient is curcumin and it has
a distinctly earthy, slightly bitter, slightly hot peppery flavor
and a mustardy smell.
In medieval Europe, turmeric became known as Indian saffron,
since it was widely used as an alternative to the far more
expensive saffron spice.
See Wikipedia for a description of
traditional dyes of the Scottish Highlands to see what
colours were available for Scottish kilts?
In 1853, when William Henry Perkins (1838-1907) was only 15, he
entered the Royal College of Chemistry in London (now part of
Imperial College London), and began his studies under August
Wilhelm von Hofmann.
For an introduction see the TED lecture by
Susan Clark on synthetic dyes.
Hofmann had published a hypothesis on how it might be possible to
synthesise quinine, an expensive natural substance much in demand
for the treatment of malaria. Perkin, who had by then become one
of Hofmann's assistants, embarked on a series of experiments to
try to achieve this end. During the Easter vacation in 1856,
while Hofmann was away visiting his native Germany, Perkin
performed some further experiments and made his great discovery:
that aniline could be partly transformed into a crude mixture
which when extracted with alcohol produced a substance with an
intense purple colour.
The brilliant violet hue quickly attracted much attention,
especially following an appearance at the Royal Exhibition of
1862, by Queen Victoria wearing a silk gown dyed with mauveine
and this stimulated other chemists to carry out similar
experiments. In 1859, François-Emmanuel Verguin in Lyon,
France discovered fuchsine,
visible spectum of fuchsine)
discovery of diazo compounds by Peter Griess at the Royal College
of Chemistry in London laid the foundation for the development of
the currently largest class of synthetic dyes, namely the azo
compounds. The first true azo dye, Bismarck
visible spectum of Bismarck Brown Y and
Bismarck Brown R)
was developed by Carl Alexander Martius in 1863.
Martius was another chemist who worked for Hofmann and apparently
kept secret from him his discovery. He later moved to Manchester
and with Heinrich
Caro produced a range of dyestuffs for Roberts, Dale and
This was clearly a vibrant era for chemistry entrepreneurs
covering a quite short 1856 - 1864 time frame as shown by the Table below of the
leading coal tar dyes from that era.
|Year and product
(date of discovery shown if different from year of first
||aniline purple, mauve (1859)
||commercial aniline/ potassium dichromate
||commercial aniline/stannic chloride
||commercial aniline/arsenic acid
|Girard and de Laire
||aniline red + aniline
||commercial aniline/copper salts
||residue of Caro's mauve process
||aniline red + aldehyde
|Caro, (Mùller Kolbe and Schmitt; Persoz 1859)
||aurin(e), yellow coralline
||phenol + oxalic acid + sulfuric acid
||picric acid + potassium cyanide
||direct application of aniline to cotton during printing
||by-product of magenta manufacture (Nicholson's process)
||trimethylrosaniline and triethylrosaniline
||aniline red + alkyl halides
|Martius and Caro
||azobenzene + aniline
|Martius and Caro
||nitrous acid on aniline
|Martius and Caro
||Bismarck brown (c.1870), Manchester Brown, Vesuvin
||nitrous acid on m-diaminobenzene
|Martius and Caro
||Manchester yellow, jaune d'or (France), chrysonaphthalic
acid, dinitronaphthylalcohol, dinitronaphthalinic acid,
binitrohydroxynaphthalene, naphthalene yellow
||naphthylamine > diazotise > naphthol +
Perkin's new colour fell out of fashion by the late 1860s, but he
soon discovered two new dyes, Britannia Violet and
Perkin's Green (the water in the nearby Grand Union
Canal was said to have turned a different colour every week-
depending on what dyes were being made at the time). In 1869,
Perkin synthesised the vivid natural red dye called Alizarin
visible spectum of alizarin)
The German company BASF beat him to the patenting process by one
day! Perkin and BASF came to an agreement over the manufacturing
processes (Perkin would sell Alizarin in Britain, some 400 tons a
year and BASF to the rest of the world) but the heyday of
synthetic dye manufacturing at Perkin's plant was now waning
(allegedly because British universities were not producing a
sufficient supply of chemists for the constant innovation now
required in the dye industry) and in 1874, Perkin sold his
dyeworks to Brooke, Simpson and Spiller. It continued operation
under its new owners only until 1876, when it was sold to the tar
makers Burt, Boulton and Haywood, the dye operations of which
joined the British Alizarine Company. This in turn became part of
ICI in 1931, and in more modern times became known as Zeneca, a
company which can claim to be the successor of Perkin.
Not long after that Chrysoidine was discovered by O. N. Witt in
Congo Red, by P.Böttiger in 1883, the first
dyestuff capable of direct application to cotton.
At the same time came the first determinations of the structures
of natural dyes and the artificial production of them. The first
of these can be considered as alizarin, then indigo (1870-1890).
In 1901 the first anthraquinone vat dye, indanthrone
was discovered by R. Bohn.
The possible relationship between composition and colour on the one hand,
and fastness on the other, were the subject of several attempts at theoretical
explanations. One in particular was the theory of O. N. Witt on chromophores
and auxochromes, and the theory - valid only in special cases - of
E. Schirm, J. Prakt. Chem., 144 (1936) 69, concerning the connexion between
composition and affinity to cellulose fibre.
Tuning Azo dyes for different colours
See for example
Tuning Azo dyes.
Modifying the substituents on a ring can influence solubility as well as changing the colour.
This can be seen from the Table below where the following effects of
substituents are shown:
Adding groups of increasing electron-donating ability to the azobenzene
structure has a
bathochromic effect (shift to higher wavelength, lower energy).
- Electron-donating (NH2) and electron-accepting (NO2) groups placed in
conjugation provide a bathochromic effect.
In this regard, nitro groups are especially beneficial, contributing to their
prevalence in disperse dye structures.
- Increasing the number of electron-attracting groups conjugated with the
electron-donor has a bathochromic effect.
- The electron-donating effects of an amino group are enhanced by adding alkyl
groups to the N-atom.
1 λ=320 nm
2 λ=375 nm
3 λ=470 nm
4 λ=520 nm
5 λ=578 nm
Another paper on tuning of azo-dyes is at
J. Biomed. Opt. 20(9), 095003 (Sep 03, 2015). doi:10.1117/1.JBO.20.9.095003
Apart from the colour they produce, dyes may be characterised by
the method of their application to the fabric. For example:
- Acid dyes
- anionic dyes applied to fibers such as silk, wool, nylon and modified
acrylic fibers under acidic conditions
- Basic dyes - usually water soluble cationic dyes that are mainly
applied to acrylic fibers, but find some use for wool and silk.
dyes - addition of the 2 components to make the azo dye directly on
or within the fibre
dyes - applied to cotton, paper, leather, wool, silk and nylon.
in aqueous solution containing NaCl
- Vat dyes -
normally insoluble but made soluble by addition of base. This
includes many of the dyes mentioned earlier like indigo.
- Disperse dyes - insoluble so they are applied from an aqueous
dyes - mordant, often chromium, is added to the textile then
Disperse dyes used mainly to dye polyester, but they can also be used
to dye nylon, cellulose triacetate, and acrylic fibers.
The 5 most widely used dyes (1996).
Disperse blue 79
|Sulphur black 1
|Reactive dye black 5
|Acid black 194
A dye with one of the largest molar absorbances (ε).
ε= 112000 m2 mol-1 with λmax =460 nm
JAIC 1992, Volume 31, Number 2, Article 7 (pp. 237 to
World Records in Chemistry, H-J. Quadbeck-Seeger (ed), Wiley-VCH,
1999, Weinheim, Germany
BBC articles on colour
Much of the information in these course notes has been sourced
from Wikipedia under the Creative Commons License. Students
taking this course will be encouraged to contribute to Wikipedia as
a part of their course assignments.
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