2. Dyeing is a method that imparts beauty to the
textile by applying various colors and their shades
onto fabric. Dyeing can be done at any stage of
the manufacturing of textile- fiber, yarn, fabric, or
a finished textile product including garments and
apparel. 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.
3. Dyes
Dyes are used for coloring the fabrics. Dyes are
molecules that absorb and reflect light at specific
wavelengths to give human eyes the sense of
color. There are two major types of dyes – natural
and synthetic dyes. Natural dyes are extracted
from natural substances such as plants, animals,
or minerals. Synthetic dyes are made in a
laboratory. Chemicals are synthesized for making
synthetic dyes. Some of the synthetic dyes contain
metals too.
4. Direct (substantive) Dyes
Direct (substantive) Dyes color cellulose fibers
directly without the use of mordants. They are
used for dyeing wool, silk, nylon, cotton, rayon,
etc. These dyes are not very bright and have poor
fastness to washing although they are fairly fast to
light.
Mordant Dyes
The mordant or chrome dyes are acidic in
character. Sodium or potassium bichromate is used
with them in the dyebath or after the process of
dyeing is completed. This is done for getting the
binding action of the chrome. They are mostly
used for wool which gets a good color fastness
after treatment with mordant dyes. They are also
used for cotton, linen, silk, rayon and nylon but
are less effective for them
5. without thickeners because the mixing up of
resins, solvents and water produces thickening
anyway.
Synthetic Dyes
Synthetic dyes are classified based upon their
chemical composition and the method of their
application in the dyeing process.
Basic (Cationic) Dyes
Basic (Cationic) Dyes are water-soluble and are
mainly used to dye acrylic fibers. They are mostly
used with a mordant. A mordant is a chemical
agent which is used to set dyes on fabrics by
forming an insoluble compound with the dye. With
mordant, basic dyes are used for cotton, linen,
acetate, nylon, polyesters, acrylics and mod
acrylics. Other than acrylic, basic dyes are not
very suitable for any other fiber as they are not
fast to light, washing or perspiration. Thus, they
are generally used for giving an after-treatment to
the fabrics that have already been dyed with acid
dyes.
