Difference between dye and pigment.

Published on 15-Jul-2022

 

Dye:A coloured substance is known as dye when that can fixed upto the substrate and when fixed is not fugitive e.g. fast to light and not washable by water, dilute acid or alkali. Many natural dyes had been known and they were derived from both vegetable and natural sources. Now a day’s most of the dyes are synthetic and are prepared from aromatic compound. E.g. Coal-tar

Acid dye                               Na          =Na+ +A- (coloured acid)

Basic Dye                             BCl          =B+ (colored)   

 

Dye or dyestuff: A dye or dyestuff is usually a coloured organic compound or mixture that may be used for imparting colour to a substrate in a reasonably permanent fashion. A dyed substrate should be resistant to a normal laundry or cleansing procedure and stable to light.

Optical brightness or whiteness which has the special properties of absorbing ultraviolet light and re-emitting the visible light to appear the substrate bright is called white dyes. They are colourless compound.

Dyes in a coloured substance but all coloured substance are not dyes. Thus a dye should fix itself on the substrate to give a permanent coloured appearance.

 

 

 

Points of difference

Dyes

Pigments

  1. Solubility

They are soluble in water & most of  the solvents

Pigments are not soluble in water & most of the solvent

  1. Number

Available in large number

Comparatively lesser in number

  1. Product Resistance

Lower as compared to pigments

Very high

  1. Light fastness

Low light fast

more light fast

  1. Size

Dye molecules are comparatively smaller

Pigment molecules are comparatively bigger.

  1. Imparting of colors

Only can impart color by selective absorption of dyes

Impart color by either scattering of light or by selective absorption

  1. Chemical composition

Usually the dyes are organic components

They are normally inorganic components often involving very toxic

  1. Fixation

Dye fixation occurs throughout the cross-sectional area of leather

Pigments only suspend on the surface of leather.

 

  1. Structure during application

Temporary alter in the structure.

They retain particulate or crystalloid structure.

 

 

 

 

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