# Colour and protection: dyes, pigments, paints and coatings

How molecules become coloured, how dye intermediates and azo dyes are made from benzene, toluene and naphthalene, and which dye classes suit which fibres. It then covers titanium dioxide, carbon black and organic pigments, and how paints and inks are formulated and made, with the economics and Indian industry data throughout.

Source page: https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/

[Understanding Chemicals](https://www.materialinsights.org/learn/chemicals/) / Module 8

## Colour and protection: dyes, pigments, paints and coatings

How molecules become coloured, how dye intermediates and azo dyes are made from benzene, toluene and naphthalene, and which dye classes suit which fibres. It then covers titanium dioxide, carbon black and organic pigments, and how paints and inks are formulated and made, with the economics and Indian industry data throughout.
 5 parts · 19 sections · about 50 minutes · 0 of 5 parts read

### By the end you will be able to

- Explain why some molecules are coloured and why solubility separates dyes from pigments.
- Trace how benzene, toluene and naphthalene become dye intermediates and azo dyes, using raw material figures per tonne.
- Match the main dye classes to the fibres they suit and identify what dyeing leaves in the effluent.
- Compare the sulphate and chloride routes to titanium dioxide and describe how carbon black and organic pigments are made.
- Describe what a paint contains, how it is manufactured and why its economics turn on raw materials and formulation know-how.

### Contents

1. [Part 1 Why things look coloured: chromophores, dyes and pigments](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p1/)

Every colorant on the market, from the blue of denim to the white of a wall, works by removing some wavelengths of light and returning the rest. This part covers what makes a molecule coloured, what makes it stick to a fibre, and the one property that splits the business in two: whether the colorant dissolves.

  - Colour is the light a molecule does not absorb
  - Chromophores give colour; auxochromes make it soluble and make it stick
  - Dye or pigment: the dividing line is solubility

2. [Part 2 From benzene to azo dye: intermediates and dye manufacture](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p2/)

Dyes are not made from crude aromatics in one step. They are assembled from intermediates: benzene, toluene or naphthalene rings carrying nitro, amino, sulphonic acid, chloro or hydroxy groups. This part follows the few unit reactions involved, checks the raw material bill for aniline against the chemistry, and ends with a real azo dye batch sheet.

  - Intermediates are the building blocks, and the hard part is getting the right isomer
  - Nitration and reduction: benzene to nitrobenzene to aniline
  - Sulphonation, chlorination and fusion steer groups onto the ring
  - Diazotisation and coupling: how an azo dye is made

3. [Part 3 Dye classes, fibres and the dyehouse](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p3/)

A dye is useless unless it suits the fibre. Cotton, wool, nylon and polyester differ in chemistry and in how much water they take up, and each dye class was invented to fit one of them. This part matches classes to fibres, explains the largest classes, and follows the dye through the dyehouse into the effluent.

  - The fibre decides the dye class
  - Reactive and disperse dyes: the two big classes
  - Vat and sulphur dyes: insoluble colours made soluble for a while
  - How dyeing is done, and what leaves in the water

4. [Part 4 Pigments: titanium dioxide, carbon black and organic pigments](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p4/)

A pigment works by staying solid. In a paint, ink or plastic it scatters or absorbs light, hides what lies beneath and shields the binder from sunlight. This part explains hiding power, follows the two routes to titanium dioxide, and covers carbon black and organic pigments.

  - Hiding power comes from refractive index and particle size
  - Titanium dioxide by the sulphate route: cheap ore, heavy waste
  - The chloride route, and why India stayed mostly with sulphate
  - Carbon black and organic pigments: two very different businesses

5. [Part 5 Paints, coatings and inks: formulation, manufacture and markets](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p5/)

Paint is where many of the chemicals in this module meet: titanium dioxide, extenders, organic pigments and carbon black, held in a resin and thinned with water or solvent. Making paint is mostly physical mixing, so the economics turn on raw materials, formulation skill and distribution rather than on reactors. This part covers formulation, technologies, the paint factory and the main markets, with Indian data.

  - A paint is pigment dispersed in a binder, carried by a solvent
  - Solvent-borne, water-borne, powder, high solids and radiation cure
  - Making paint is mixing, milling and tinting in batches
  - Industrial coatings, decorative paint and printing inks

6. [Wrap-up Key terms, try it in the table, final quiz, sources](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/review/)

[Start: Part 1, Why things look coloured: chromophores, dyes and pigments →](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p1/)

## Other sections

- [Why things look coloured: chromophores, dyes and pigments](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p1/index.md)
- [From benzene to azo dye: intermediates and dye manufacture](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p2/index.md)
- [Dye classes, fibres and the dyehouse](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p3/index.md)
- [Pigments: titanium dioxide, carbon black and organic pigments](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p4/index.md)
- [Paints, coatings and inks: formulation, manufacture and markets](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/p5/index.md)
- [Key terms, quiz and sources](https://www.materialinsights.org/learn/chemicals/dyes-pigments-coatings/review/index.md)