The Differences Between Interior & Exterior Paint

Take a tour through the paint aisle at your local hardware store and you’ll find hundreds of different kinds of paint, each claiming to be the best option for one application or another.

Often the biggest distinctions that get made between interior and exterior paints, with cans loudly proclaiming their ability to stand up to the Australian sun. But does it really matter which kind of paint you use as long as the colour is right?

We’re going to look at the differences between indoor and outdoor paints to see how they are made and which one you should be choosing for your next painting project.

How Paint is Made

All paints are made of a few basic ingredients, and it’s these ingredients that determine how long the paint lasts, how well the colour holds, and whether the paint is capable of standing up to things like UV rays and rain. Both interior and exterior paints contain:

  • Solvent. In most modern paints water is the only solvent used. It’s better for the environment and easier to clean up, but oil paints typically allow for a higher sheen and slightly tougher finish, making them more common in exterior paints.

  • Pigment. The pigment determines the colour of your paint, and it also contains other additives that the paint needs, like UV protection or fungicides commonly found in exterior paints. When you apply the paint, the solvent evaporates, leaving just the pigments and the additives bonded to the surface.

  • Resin. Those pigments and additives are bonded to the surface with a resin. Epoxy, silicone and acrylic are all common resins found in paint, and each comes with its own strengths and weaknesses. Since exterior paint usually needs to be a little tougher, it often uses harsher resins with better bonding properties, such as epoxy.

Understanding the Differences

Since all paints are made of these simple components, it’s a fair question to ask what makes them different.

Interior paints are designed to live their lives inside the house where the risk of UV or weather damage is low and you need to keep chemicals in the air to a minimum. In a process called off-gassing, products like a paint can release particles and chemicals into the air that are harmful to breathe. While most modern paints pose little risk to homeowners, long-term exposure to these airborne chemicals can cause lung irritation or other complications, especially in people who are prone to respiratory problems.

Alternately, exterior paints are designed with tougher resins and harsher additives that are perfect for ensuring the paint can stand up to the elements. But those harsh additives mean exterior paints have more volatile chemicals that shouldn’t be breathed. While most off-gassing of chemicals happens within the first few days of a new paint job, some paints continue to release chemicals into the air for many years, increasing the risk to your health.

Can Interior and Exterior Paints Be Substituted?

The short answer to this question is that it depends on the type of paint and where you want to put it. In most cases, interior paints will not be suitable for outdoor applications. They simply won’t withstand the sun and the rain and will fade or flake away much sooner than they should.

Using exterior paints inside the house is a little different. While the risk of off-gassing and harmful chemicals is real, most people are unlikely to notice the effects. Typically long-term exposure to these chemicals is harmful, so professional painters need to be cautious, but homeowners are less at risk. If your paint claims to have fungal or mould killing properties then you should avoid using it in enclosed spaces. These chemicals are much more harmful when breathed and should only be used outdoors.

Need Help With a Painting Project? Contact McAuliffe Painting Today!

If you’re getting ready to tackle a painting project and need some help, please don’t hesitate to get in touch with McAuliffe Painting. Our expert team has worked on projects of all shapes and sizes, and we can help you choose the right paints that will stand up to the task while keeping your family happy and healthy.

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