What’s the Difference Between Interior & Exterior Paint?

Does it really matter if I use my leftover interior paint to freshen up the outdoor patio area? Can I use my leftover exterior paint to revamp the kitchen walls? Since all paint is used to decorate, protect, prolong the life of materials and act as a barrier against various environmental conditions, what is the actual difference between interior and exterior paint?

Firstly, let’s have a simple science lesson on the chemicals in a can of paint. While oil and water-based paints do have some chemical differences, all paints contain: –

Pigment – gives the paint it’s unique colour.
Additives – keep the pigment distributed evenly in the paint solution, improve weather resistance, control mildew and regulate the drying time.
Solvent – is used to suspend the chemicals in the paint can, but evaporates after the paint has been applied.
Extender –is a naturally occurring chemical substance added to paint to improve its properties such as durability, cost and resistance to corrosion or wear.
Polymers – are coating chemicals that actually form the film of the surface.

These ingredients are formulated according to a particular “recipe” with differing percentages of each paint component mixed to fine-tune them for their intended use.

The primary difference between interior and exterior paints is the type of resin used:

Exterior paint needs to be tough enough to withstand a variety of weather conditions throughout the seasons of the year. It is also designed to be flexible and resist mildew, peeling, chipping and fading from sunlight. Therefore, the resins used in binding exterior paints must be softer. Exterior paint also releases more VOCs (potentially toxic compounds) into the air which makes them quite dangerous to use indoors and can lead to allergies.
The resins used in interior paint are more rigid, which enables the paint to resist staining as well as allowing the painted surfaces to be cleaned and even scrubbed for easier maintenance.

It may be tempting to use your leftover paint for a project it was not intended for, however be forewarned that the end result will not look as good, or last as long. Both manufacturers and professional painters recommend you choose the right paint for the job at hand.

Firstly, let’s have a simple science lesson on the chemicals in a can of paint. While oil and water-based paints do have some chemical differences, all paints contain: –

These ingredients are formulated according to a particular “recipe” with differing percentages of each paint component mixed to fine-tune them for their intended use.

The primary difference between interior and exterior paints is the type of resin used:

It may be tempting to use your leftover paint for a project it was not intended for, however be forewarned that the end result will not look as good, or last as long. Both manufacturers and professional painters recommend you choose the right paint for the job at hand.

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