What Is Paint, Anyway?
We use the word “paint” in many ways. In addition to the product that we put onto walls and canvases and cars and furniture and all kinds of other surfaces, we also use the word to refer to the substances women (“paint”) and Native American braves (“war-paint”) put on their faces; we use it to describe a good time when we “paint the town red”; and we use it about reputations, i.e., “he’s not as bad as he’s painted”.
Actually, paint has a very specific definition: it is a solid coloring substance dissolved in a liquid or resin that, when applied to a surface, turns into a solid. Paints generally consist of three substances:
- A binder, which provides adhesion, gloss, durability, flexibility and toughness to the paint and affects application properties such as flow and leveling. It may be a natural resin such as an oil or alkyd, or even egg; or a synthetic like acrylic, polyurethane, polyester, or epoxy. Oil-based binders usually refer to oil and alkyd coatings; linseed oil has been the most popular oil-based binder. Water-based binders are found in most water-based (or latex) paints. Many binders, however, are too thick to apply to a surface and must be thinned.
- A solvent, which determines the viscosity of the paint, temporarily rendering it liquid and capable of being applied to a surface. For most oil- or alkyd-based paints, the solvent is paint thinner; for shellac-based paints, the vehicle is denatured alcohol. Water is the thinner for latex-based paints. Some paints do not require a solvent.
- A pigment or dye made from ground solids of one kind or another, which contributes the color. Titanium dioxide is the primary white pigment, and provides extreme whiteness by scattering light. Color pigments, organic or inorganic, provide color by selective absorption of light.
When the solvent has finished evaporating from the applied liquid containing the binder with the pigment dissolved in it, the binder is fixed to the surface as a solid film.