ChemicaLife
Pigment Chemistry: How Color, Opacity and Durability Work
Why does a strong blue barely hide a pencil line? Why do two white paints cover differently? Why can a vivid color fade while a duller one lasts? Pigment chemistry helps explain these everyday observations, but the finished paint, ink or plastic matters as much as the name of its colorant.
This guide introduces the useful distinctions and helps you decide what to check next. It focuses on materials used for color, not biological pigments in skin or medical conditions.
What does a pigment do?
A pigment consists of small solid particles dispersed in a material. A binder can hold those particles in a dried paint film; a plastic can hold them throughout its body. The particles affect which wavelengths of light are absorbed and how light is scattered. The result depends on the colorant, surrounding material, particle arrangement and illumination.
Think of a painted surface as a system: light reaches a film, interacts with the particles and binder, and may also reach the surface underneath. Changing the film thickness or background can change what you see even when the pigment name stays the same.
| Question | Property to investigate | Useful evidence |
|---|---|---|
| Will the old color show through? | Opacity or hiding power | A dry sample at the recommended application rate |
| Will a little color strongly change a mixture? | Tinting strength | A controlled mixture with the same white or base |
| Will it retain its appearance? | Lightfastness and other durability properties | The exact product’s test method, rating and intended use |
Pigment or dye: dispersed particles versus dissolved color
The useful starting point is how the colorant behaves in its application medium. Pigments remain particulate; dyes generally operate in dissolved form during application. Water solubility alone is not a universal test. A colorant can behave differently in a different solvent or application process. For an actual ink or textile project, identify the product system before choosing a colorant.
Organic or inorganic: a chemical classification
Organic pigment families include phthalocyanines and quinacridones; inorganic families include metal oxides such as iron oxides and titanium dioxide. These labels do not tell you whether a product was made from plants, manufactured synthetically or approved for a particular use. Ask for the pigment identity and application data instead of treating one family as universally better.
Opacity: why a vivid color may still be transparent
Hue, tinting strength and hiding power describe different things. A transparent artist’s color can make a strong blue mixture without concealing the marks underneath a thin layer. For a wall coating, compare dried samples on the same background and follow the product’s spreading-rate instructions. Do not judge hide from a thick blob on a mixing stick.
Titanium dioxide: a common route to white and opaque films
Titanium dioxide, often labeled PW6 in artist materials, is widely used as a white pigment. Its optical role is to scatter visible light. The pigment grade, dispersion and coating formulation influence the result, so a TiO₂ ingredient listing does not establish one-coat coverage or exterior suitability.
Durability: start with the actual rating system
Lightfastness concerns color change under light exposure. Weather resistance also concerns stresses such as moisture and temperature. A lightfast artist’s paint is not automatically an exterior coating. Read the manufacturer’s rating legend and any conditions attached to it; a missing rating is missing evidence, not proof of either failure or permanence.
Glowing materials: emission is different from reflection
A fluorescent material can emit light while being excited by suitable illumination. Some photoluminescent materials show an afterglow. An ordinary bright paint does not necessarily do either. For a glow effect, specify whether you need brightness under a lamp or continued emission after the lamp is switched off.
A five-part label checklist
- Product: record the brand, range, color and intended surface.
- Identity: note the Colour Index code if provided; a color name alone may describe a blend.
- Appearance: check opacity and the recommended film thickness or application rate.
- Durability: identify the rating system and the conditions behind the claim.
- Use: follow the finished product’s directions and restrictions. A pigment name does not authorize a new use.
Read the detailed guides
This collection grows as each guide is published. The list below shows available articles only.
Sources and editorial scope
- Color Pigment Manufacturers Association: Pigment FAQs
- GOLDEN: Acrylic label information
- Li Yuanyuan, 颜料化学与工艺学 (Pigment Chemistry and Technology), Chemical Industry Press, 2020. ISBN 978-7-122-36005-2. Background reading: Chapter 2, pp. 9–16; Chapter 4, section 4.2.