The Difference Between Interior and Exterior Paints
Have you ever wondered what they put in paint that make them worthy of being used inside versus outside. Common logic would tell you that an exterior paint is a better paint and that it would make sense to use it inside. The thinking behind this is that any paint that can withstand the elements must surely be a better paint and therefor a product that can and should be used in the home.
You might be surprised to discover that is not the case.
Paint Attributes:
The four parts to Paint: Solvents, resins, additives and pigments.
Solvent, which is usually in the form of water (for latex paints) or mineral spirits (for oil paints), is what makes paint wet. Lower-quality paints use more solvents than resins, additives or pigments. The solvent evaporates as the paint dries, leaving only the resins, additives and pigments on the wall.
Resins bind the pigment (color) to the wall and are made of acrylic, silicone or epoxy.
Additives are additional chemicals added to paint to change a property of the paint. Some additives prevent mildew or fading. Others make the painted surface easier to clean. And some make the paint chip-resistant or make it easier to apply. There is a variety of additives to suit a variety of applications.
Pigment is the actual color added to the paint. It is usually added in powder form and does not dissolve but is suspended in the solvent and bound to the wall by the resin.
Interior Paints:
Waterbase interior paints are typically made of vinyl acrylic or latex acrylic polymers that bond well to interior surfaces, cure without direct sun exposure, are low in odor, and are best at leveling and hiding brush and roller marks.
Exterior Paints:
Exterior paint is formulated for: Color retention; Resistance to fading; Flexibility to withstand expansion and contraction due to weather; To provide a mildew resistant coating; Resistance to tannin bleed.
They also contain mildicides, fungicides, pesticides: What is in the paint and how much all depends on what the paint is being used for.
So – you should not mix interior and exterior paints, or use them for anything other than their purpose. Exterior paints are designed to be used outside, with sunlight adding in the cure, while interiors, typically waterbased, do not require direct sunlight to cure.
