Interior vs Exterior Paint: Everything You Need to Know

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What’s the difference between interior and exterior paint? Isn’t all paint the same? Does it really matter if you use leftover exterior paint to spruce up the laundry room or a guest bedroom? Can I use my extra dining room paint to freshen up the entryway door? 

Professional painters know the real deal, but everyday people may not be sure of the right answers. That’s because nonprofessionals don’t know about the science behind a tin of paint. For example, water-based and oil paints do have a few chemical differences yet they still all include the same six ingredients. 

Being a professional painter, you obviously know everything about how paint is made and how best it can be used. Do you also know about painters public liability insurance? You’ll discover that public liability insurance will safeguard you, your employees, and your business from financial damages and legal fees associated with negligence, including property damages and personal injuries. BizCover has an amazing platform for quick online comparison of public liability policies across multiple insurers. 

Now that you’ve learned a bit about painters public liability insurance, let’s dive into the differences among paints and why they aren’t all alike. 

6 Key Ingredients in Both Interior and Exterior Paints

The six main paint ingredients are used in a special formula, or recipe, with differing ratios depending on the type of paint. Here are the six common paint components and what they do:

  1. Pigment: This is the ingredient that gives all paint its unique colour. Exterior paint usually has more pigment since it has to stand-up to diverse conditions. 
  2. Polymers: This ingredient helps paint keep its quality. The two main types of polymer used in paints are acrylic and polyvinyl acetate. Acrylic polymers help exterior paints hold up under intense weather conditions and sunlight. Polyvinyl acetate polymers are used for interior paints because they are a cost-effective way to make the paint durable.  
  3. Additives: These ingredients help improve weather resistance, keep mildew under control, regulate the paint’s drying time, and help keep the pigment distributed evenly. 
  4. Solvent: This ingredient suspends the paint chemicals within the can but quickly evaporates after the paint has been applied. 
  5. Binder: This ingredient is also known as “resin”. Binders prevent all the different chemicals from separating. It also helps the paint adhere to the surface of the item being painted. 
  6. Extender pigment: This ingredient is added to most paints to improve its durability and resistance to corrosion and wear. Extender pigment is a chemical also used in soap and lotion. 

The Type of Resin for Interior vs Exterior Paint

Professional painters know resin are compounds added to paint for three reasons. First, resin can hold together paint until it can dry, oxidize, and solidify. Second, resin helps paint dry with a beautiful clarity. Finally, pro painters understand that resin can be used to dilute paint without thinning it out too much. This helps the paint dry faster. 

The bottom line: resin is critical to high quality paint because it holds the pigment (colour), makes it durable, and helps the paint stick to the surface. The main difference between an interior paint and an exterior paint is the resin. Check out the details below. 

  • Exterior Paint: Paints used for sidings and trim, lawn furniture, and other outside surfaces need to be sturdy. The paint you use outside will need to stand up to diverse weather, including sunlight and water exposure. The resin used in exterior paint must help the material withstand mildew, chipping, peeling, and fading. Plus, as a professional painter, you know that exterior paint releases far more potentially toxic VOC vapors and gases which are only safe outdoors. If someone uses exterior paint inside the house, they are exposing the home’s occupants to harm and a potential health crisis. 
  • Interior Paint: Resins used for interior paint are not as flexible as those in exterior paints. For this reason, interior paint resins will resist staining. This makes interior paint much easier to clean and less likely to scuff which homeowners love. Of course, interior paint doesn’t need the same resin as exterior because the paint is protected from mother nature, like direct sun, rain, snow, mildew, and mold. Interior paint has low or zero VOCs vapors which will keep the home’s occupants safe from breathing in hazardous chemicals.  

Although it can be tempting to use leftover paint for new projects, it’s important to use the correct paint for the job. If someone skips picking the right coverage, they may be disappointed with the results. The quality will be compromised, and the paint may not hold up to its environment. Professional painters know picking the right paint formula is critical to having a good outcome. 

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