ORGANIC DYES DYE LASER ACID DYES BASIC DYES SUBESTANTIVE
Dyeing is the process of importing
color to a textile material in loose
fibre, yarn, cloth or
garment form by treatment with a dye.
DYE can generally be described as a colored substance that has an
affinity to the substrate to which it is being applied. The dye is
generally applied in an aqueous solution, and may require a mordant
to improve the fastness of the dye on the fiber.
The term direct dye
application stems from some dyestuff having to be either fermented
as in the case of some natural dye or chemically reduced as in the case of
synthetic Vat and Sulphur dyes before being applied. This renders
the dye soluble so that it can be absorbed by the fibre, the
insoluble dye has very little substantively to the fibre. Direct
dyes, a class of dyes largely for dying cotton, are water soluble
and can be applied directly to the fibre from an aqueous solution.
Most other classes of synthetic dye, other than vat and sulpur dyes,
are also applIed in this way.
The term may also be applied to dyeing without the use of mordant to fix the dye once it is applied.
Mordant were often required to alter the hue and intensity of
natural dyes and improve their color fastness. Chromium salts were until recently extensively
used in dying wool with synthetic mordant dyes. These were used for
economical high color fastness dark shades such as Black and Navy.
Environmental concern have now restricted their use and they have
been replaced with reactive and metal complex dyes which need no
There are many forms of yarn
dyeing. Common forms are -at package form & at honks form.
Cotton yarns are mostly dyed at package form, and acrylic or wool
yarn are dyed at hank form
The common dyeing process of cotton yarn with reactive dyes at
package form is given below in short- firstly the raw yarn is winded
on spring tube to achieve package suitable for dye penetration.
then, these softened packages are loaded on a dyeing carrier's
spindle one on other. Then, the packages are pressed up to a desired
height to achieve suitable density of pkg. then, the carrier is
loaded on dyeing machine and yarn is dyed. after dyeing, the
packages are unloaded from the carrier in to a trolly. then, all the
packages are hydro extracted to remove maximum amount of water.
then, all the packages are dried to achieve the final dyed package.
at last the dyed yarn packages are packed and delivered
Both dyes and pigments appear to be colored because they absorb
some wavelengths of light preferentially. 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.
Archaeological evidence shows that, particularly in India and the
Middle East, dyeing has been carried out for over 5000 years. The
dyes were obtained from animal, vegetable or mineral origin, with no
or very little processing. By far the greatest source of dyes has
been from the plant kingdom, notably roots, berries, bark, leaves
and wood, but only a few have ever been used on a commercial
scale.Color is the most important
attribute to consumers . The colors in fabrics are infinite. They
can be solids, multi-colored stripes, or other pattern effects such
as floral and geometries. Dyeing of the material can be done at any
stage of making the fiber, yarn, or fabric. The desired effect to be
achieved will usually dictate the dyeing
For example, a
multi-colored floral pattern requires the individual yarns to be
pre-colored to as many different shades as there are in the desired
pattern. The various colored yarns are then constructed into the
floral pattern fabric.
contrast a solid color can be achieved by constructing
the fabric first and then dyeing the fabric. Another way to achieve
a solid color or multi-color effect would be to use pre-dyed fiber,
produce the colored yarn, and then construct the fabric. This
assures consistently uniform color. Printing is localized coloration
that also achieves multi-colored effects.
provide a wide range of finishing options, from scouring and
prepare-for-print to a variety of soft to medium finishes to meet
our customers' requirements. In addition, we also provide specialty
finishes including soil resistant finishes, anti-microbial and
coloration. This treatment can be mechanical, chemical, or both. The
mechanical treatment is done at the textile mill or dye house. It
can be one of various surface treatments. Brushing and sanding of
fabrics, for example, can provide extra sheen and
A dye laser is a laser which
uses an organic dye as
the lasing medium, usually as a liquid solution.
Compared to gases and most solid state lasing media, a dye can usually be
used for a much wider range of wavelengths. The wide bandwidth makes them
particularly suitable for tunable lasers
and pulsed lasers. Moreover, the dye can be replaced by another type
in order to generate different wavelengths with the same laser,
although this usually requires replacing other optical components in
the laser as well.
The long-wavelength absorption band of laser dyes is attributed
to the transition from the electronic ground state S0 to
the first excited singlet state S1. The transition moment
for this process is typically very large, thus giving rise to an
absorption band with an oscillator strength on the order of unity.
The reverse process S1->S0 is responsible
for the spontaneous emission known as fluorescence and for the
stimulated emission in dye lasers.
Dye lasers are also used dermatologically, to make skin tone
Close-up of a table-top dye laser based on Rhodamine 6G, emitting at 580 nm
(yellow-orange). The emitted laser beam is visible as faint yellow
lines. The orange dye solution enters the laser from the left, and
is pumped by a 514 nm (blue-green) beam from an argon laser. The dye
jet is in the center of the image, behind the yellow window.
The first human-made (synthetic) organic dye, mauveine, was discovered by William Henry Perkin in 1856. Many thousands of synthetic dyes have
since been preparedSynthetic dyes quickly replaced the traditional
natural dyes. They cost less, they offered a vast range of new
colors, and they imparted better properties upon the dyed materials.
Dyes are now classified according to how they are used in the dyeing
Acid dyes are water-soluble anionic dyes that are applied to fibers such as silk,
and modified acrylic fibers using neutral
to acid dyebaths. 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
Basic dyes are water-soluble
cationic dyes that are mainly applied to acrylic
fibers, but find some use for wool and silk. Usually acetic acid is added to the dyebath to help the
uptake of the dye onto the fiber. Basic dyes are also used in the
coloration of paper.
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).
Direct dyes are used on cotton, paper,
leather, wool, silk and nylon. They are also used as pH indicators and as biological stains.
Dyeing is a dye used in a
process in which dye molecules are attracted by physical forces at
the molecular level to the textile. The amount of this attraction is
known as "substantively": the higher the substantively the greater
the attraction of the dye for the fiber).
Mordant dyes require a mordant,
which improves the fastness of the dye against water, light and perspiration. The choice of mordant is very
important as different mordant can change the final color
significantly. Most natural dyes are mordant dyes and there is
therefore a large literature base describing dyeing techniques. The
most important mordant dyes are 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. It is important to note that many mordant,
particularly those in the hard metal category, can be hazardous to
health and extreme care must be taken in using them.
(A mordant is a
substance used to set dyes on fabrics by forming an insoluble
compound with the dye.)
Cellulose is an organic compound with
the formula (C6H10O5)n.
utilize a chromophore
containing a substituent
that is capable of directly reacting
with the fibre substrate. The covalent
bonds that attach reactive dye to
natural fibers make it among the most permanent of dyes. "Cold"
reactive dyes, such as Procion MX
, Cibacron F
, and Drimarene
, are very easy to use because the dye can be applied at
room temperature. Reactive dyes are by far the best choice for
and other cellulose
fibers at home or in the art
In a reactive
dye a chromophore contains a substituent that is
activated and allowed to directly react to the surface of the
A chromophore is
part (or moiety) of a molecule responsible for its
are two part
"developed" dyes used to dye cotton with dark colors. The initial
bath imparts a yellow or pale chartreuse
color. This is oxidized
in place to produce the dark black
we are familiar with in socks and the indigo blue of the common
dyes are the biggest volume
manufactured for cotton
Redox (shorthand for reduction/oxidation reaction)
describes all chemical reactions in which
atoms have their oxidation number (oxidation state) changed.This can be either a simple redox process such as the
oxidation of carbon to yield carbon dioxide, or the reduction of carbon by
hydrogen to yield methane (CH4), or it can be a
complex process such as the oxidation of sugar in the human body through a series of
very complex electron transfer
processes.The term redox comes from the
two concepts of reduction and oxidation. It can be
explained in simple terms:\\
describes the loss of electrons by a molecule, atom or
describes the gain of electrons by a molecule, atom or
ion .Top of
However, these descriptions (though sufficient for
many purposes) are not truly correct. Oxidation and reduction
properly refer to a change in oxidation number — the actual
transfer of electrons may never occur. Thus, oxidation is better
defined as an increase in oxidation number, and reduction as
a decrease in oxidation number. In practice, the transfer of
electrons will always cause a change in oxidation number, but there
are many reactions which are classed as "redox" even though no
electron transfer occurs (such as those involving covalent bonds).Non-redox
reactions, which do not involve changes in formal charge, are known as metathesis reactions.
is typically brightly colored, patterned textile or clothing which is made from ordinary
cloth, usually cotton, through a resist
dyeing process known as tie-dyeing. This is the modern
version of a traditional dyeing method.
Resist dyeing, resist-dyeing and variants
is a term for a number of traditional methods of dyeing textiles with patterns. Methods are used to
"resist" or prevent the dye from reaching all the cloth, thereby
creating a pattern and ground. The most common forms use wax, some
type of paste, or a mechanical resist that manipulates the cloth
such as tying or stitching. Another form of resist involves using a
chemical agent in a specific type of dye that will repel another
type of dye printed over the top.