Paint Pigments – What are paint pigments and what do they do?
Paint Pigments
- Pigments are fine powdered solids which provide the color and opacity (hiding power) of the paint.
- They help the film former with substrate protection, for example calcium plumbate inhibits rust on ferrous metals.
- Pigments can often contribute to the durability of the paint.
Pigments are obtained from:
- Chemically treated metals – eg. Iron oxide a yellow or red, it is used in all finishing paints, Titanium dioxide, white, is used for interior paints.
- Colored Earths – eg Yellow ochre and burnt umber are used for all types of paints.
- Treated chemical compounds – eg. Prussian blue, this is used for oil/alkyd paints.
Extenders (extender pigments)
Extenders are solid components of paint. They are finely ground natural materials, most commonly earth, and they have no effect on the colour of the paint, but they do alter some properties.
They have many varied functions:
- Provide easier application of the paint.
- Provides greater adhesive properties.
- Provides roughness in the film (i.e. undercoats).
- Gives body to the paint, increases bulk in the coating.
- Prevents heavy pigments from settling out.
- Provides a greater water resistance.
- Flatten bases.
- Reduces the cost of paints.
- Increases the hardness of the paint film.
Solvents (or Thinners)
These are colorless liquids that are included in the paint (or clear finish) and work on the binder to thin the quality of the paint. This dilutes the coating and improves the ease of application and increases penetration of the product. The solvent then evaporates after application during the drying out process.
Examples of solvents:
White spirit – used with oil and oil/resin paints.
Ethers – used with cellulose resins and synthetic finishes.
Water – used with cement and emulsion paints.
(Thinners, mineral turps, solvents, methylated spirits, alcohols and acetates).
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