Paint is a thin coating, designed to mask and protect the surface beneath. It usually consists of four components:
- Liquid (water or mineral spirits), which allows the paint to be applied, then evaporates. The liquid for latex paint is ordinary water. In oil-based paints, it is mineral spirits (paint thinner).
- Pigments – they are finely ground, naturally colored solids that, when mixed, produce the desired paint color. Prime pigments provide most of the color and give paint the ability to hide a color underneath. These include: TiO2 (Titanium Dioxide), organic pigments and inorganic pigments. Extender pigments are low-cost materials, such as clay, calcium carbonate, talc, silicas, and silicates.
- Additives – These are chemicals, added to the paint to enhance its mildew resistance, ability to stick to the surface, and to make it flow more effectively.
- Binders – Most latex (water-based) binders are 100 % acrylic or vinyl acrylic. Acrylic binders are used in exterior paints and primers and some premium interior paints because of their high adhesion (blister and crack resistance) and water resistance (fresh masonry). Vinyl acrylic binders are used in interior flat, satin, and semigloss paints, and in wall primers. Oil-based (solvent-based) binders include linseed oil, tung oil, and alkyd. The first two are natural vegetable oils, while alkyds are oils that have been modified to dry faster and harder than regular oils. A negative of alkyds is that they harden with age and become prone to chipping. They are also being phased out because of their high volatile compound (VOC) content.
Latex paints have several advantages over alkyds (oils). Latex is flexible, thins and cleans up with water, dries quickly and has nontoxic fumes. In exterior applications its ability to breathe water vapor reduces peeling and blistering.
Alkyds, however, have greater adhesion over smooth, nonabsorbent surfaces, such as plastics and metals. And they can hold a greater percentage of solids, often allowing single-coat coverage.
Sometimes the best solution is both: an alkyd primer for adhesion and hiding, a latex top coat. It all depends on the type of project you need to accomplish. The people in the nearest paint center can advise you and help you decide which option suits your needs the best. Meanwhile, here is a table with latex and alkyd`s general advantages and limitations:
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