The difference between the nature of dyes and pigments leads to vastly different uses. On one hand, dyes are mainly used in the textile and paper market whereas pigments find applications in industries like colouring paints, inks, cosmetics, and plastics. While the application of both dyes and pigments is to give colours to materials, both of them differ widely in terms of the materials they can be applied to as well as the way they function.
Dyes can be used with a dye solution dyes dissolved in water as well as directly, depending on the chemical composition of the dye and the material being dyed. Thus, it is an important part of any dyeing process is to find a material onto which the dye can attach itself. A pigment cannot be directly applied to a material. It must be done with at least two parts, although usually more are used, commonly known as the pigment and the vehicle.
The third part usually used is called Thinner. Each of the component involved has a distinct function. A vehicle is responsible for carrying the pigment to the surface whereas a thinner would be used if the vehicle is too viscous, and therefore difficult to apply on the surface.
Once a mixture of these three is applied, the thinner quickly evaporates and what remains evenly spread on the surface. The industry is one of the most widespread across the world owing to their immense applicability.
Mixing the salt with the water results in it completely dissolving in the water. So this mixture is called a solution. Pigments, like the mud in the above example, are finely ground particles of color that get suspended in a liquid usually not water, and called the dispersing agent or vehicle.
Whereas dyes are chemicals that, like the salt above, get dissolved in a medium such as water to create a colorant. How the colorant actually attaches itself to the material also differs greatly between pigments and dyes.
While dyes chemically bind with the material, pigments are painted onto the surface, so they physically bind. The pigment, mixed with the dispersing agent, is applied to the base and forms a coating on top. The dispersing agent basically makes it stick to the surface of the material. Whether the dye will attach itself or not depends on the chemical nature of the material being dyed and the dye itself. Technically speaking, the difference is that dyes are soluble in the host material—typically water—while pigments are not.
Another difference is that dyes do not scatter light and look transparent. On the other hand, pigments do scatter light and, thus, they are opaque see Fig. Still another difference between dyes and pigments is that dyes are absorbed by the colored substrate and pigments need a binding agent in order to adhere to the surface. With a suitable chemical treatment, a soluble dye can be converted into an insoluble pigment. Unfortunately, the differences between a dye and a pigment are not commonly taken into consideration, frequently causing confusion.
The definitions given in the dictionaries or used in some industries do not necessarily coincide with the technical terminology.
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