Pigment is a substance in particulate form which is insoluble in water but which can be mechanically dispersed in this medium to modify its color and light scattering properties. They are organic or inorganic colouring materials.

Pigments have no direct affinity to textile fibers. They are fixed on textile materials (fabric/yarn) with the help of a binding agent in form of a this invisible coating.

In pigments auxochrome groups are absent. A number of organic pigments are prepared from dyes by combining the dyes with a dye precipitant.

Pigment are abundant in nature. The cause of color is not only the light absorption of molecules but also the purely physical effect of optical diffraction at grating systems. Pigments are applied at thickened textile pigment coating from oil-in-water or water-in-oil emulsion systems.

Properties of pigments:

i. It is insoluble in liquids but can be mechanically dispersed in the medium.

ii. Pigments have no direct affinity towards fiber, so binding is used as a binding agent in case of pigment colouration which sticks the pigment particle on the fiber surface.

iii. Pigment are applicable to all kinds of fibers.

iv. No aftertreatment is required after coloration process, only drying and curing are required.

v. Only rubbing fastness of pigment colouration is poor, but water wash and light fastness are very good.

vi. A wide range of bright shade can be produced by pigments.

vii. In pigments auxochrome groups are absent.

Differences between dyes and pigments:

The difference between dye and pigment is not a clear one. Most organic pigments are closely related to dyes with respect to their chemical structure. There are dyes which become pigments after application. Vat dye is a dye when used in dyeing, when vat dyes are oxidized and made insoluble in fabric(after vatting) that is called pigment form of vat dyes. Vat dyes act like pigment when used in printing. Now some differences are mentioned below:

1 ) The basic difference between dye and pigment is that, dye has three parts-

i. Chromophore, which is responsible for color.

ii. Auxochrome, which is responsible for dye properties

iii. Chromogen, which holds the above two together.

But pigment has two part:-

i. Chromophore, i.e. color bearing part.

ii. Chromogen.

2 ) Pigments are insoluble in the materials that they are used to color, whereas most dyes are soluble in them.

3 ) pigments are water insoluble, but dyes are more or less water soluble.

4 ) Pigments are used as colorants in the physical for in which they are manufactured. But dyes are first dissolved in water to form a dyebath, then they diffuse as single molecules from these solutions into textile fibers to colour them.

5 ) Pigments have no direct affinity towards textile fibers but most dyes have that.

6 ) Pigments are metallic compounds may be organic or inorganic. But dyes are mostly organic compounds, few are inorganic.

Classification of pigments:-

There are mainly two types of pigments, namely,

1. Organic pigments and

2. Inorganic pigments

Organic pigments are further classified as below:-

I. Dyes converted into pigments.

It has two types,

1) Reactive Dyes made insoluble by precipitating on substrates.

2) Vat dyes converted into pigments

II. ISO indolinone pigments

III. Azo pigments:

It has two types

1) Metal free{Water insoluble azo compounds (group1)}

2)Metal containing

there are two types: chelates(group-3) and

Water soluble azo compounds(group-2)

–low soluble, make heavy metal salts(group-2a)

–high solubility precipitate heavy metal salts or basic substrates(group-2b)

IV. Quinacridone pigments

V. Phthalocyanine pigments

Inorganic pigments are classified by two types

I. White pigments and

II. Coloured pigments

There are three types of coloured pigments:

1. Ultramarine

2. Cadmium pigments and

3. Iron oxide pigments.