So, you are planning to use your leftover paint to coat your exterior door or wall or perhaps paint some patio furniture. But, can interior paint be used outside? Some experts believe it is not recommended even though people still use it. Why is that? Continue reading to find out more.
When it comes to interior paint, it is not designed to work against harsh outdoor conditions such as snow, rain, UV light, wind, mildew, or extreme temperatures. Interior paint contains less quantity of the pigment and binding resins as compared to outdoor paints. Plus, the paint is known to be too porous. Hence, this paint will eventually fade, crake, flake, and powder or chalk a lot quicker.
In this helpful article, you are going to learn all about interior paint, the components found within the paint, and why it should only be used inside one’s home. However, if you do want to use interior paint outside, there is a safe way to do it which will be explained later. Once you finish reading this article, you are going to know everything that there is about interior paint and its uses.
Interior Paint: What Is It?
Generally, interior paints are made up of a formula that is ideal for indoor usage. This type of paint is designed to stick to different types of surfaces, work against abrasion, withstand regular contact plus cleaning, and absorb or reflect light. Moreover, interior paints don’t necessarily have to survive harsh temperatures or different elements of nature.
There are four important components that make up paint:
- The base or liquid
- The additives
- The pigments
- The binders
It is the pigments, the binders, and the additives that differentiate interior paint from exterior paint. It is because of these components interior paint should not be used outside and vice versa.
Interior paints are formulated to have low quantity of VOCs (volatile organic compounds) in order to minimize health risks that can occur because of off-gassing. These volatile organic compounds make up a solvent that helps in keeping the liquid from turning hard. They are known to vaporize while the paint is drying.
All of the above-mentioned paint components are listed below in more details.
1. Bases
There are two types of interior paints in the market. There are water-based paints such as acrylic and latex paints, and there are oil-based paints like alkyd paints. So what is the difference between these two types of paints?
Both of these paints come with different uses and adhesive properties. Both of these paint types come in different sheens such as semi-gloss, high-gloss, flat, etc. if you want to test a painted surface to see which type of paint is used, you can use a cloth dipped in denatured alcohol and wipe it over the surface. If it picks up any color, it is water-based; but if it does not then it is oil-based.
If you want to paint over an oil-based painted surface with water-based paint, apply an oil-based stain lock sealer or primer before. On the other hand, you can use oil-based paints over a water-based painted surface once they are dry. However, you might have to gently scuff glossy surfaces using sandpaper.
What Are Water-Based Paints?
Paints that are water-based contain binders and pigments that are blended with water, which is their carrier. As the water evaporates, the paint dries more quickly as the color becomes more visible. As compared to oil-based paints, water-based painted surfaces are easier to clean and the color lasts for a long time. Plus, due to the presence of fewer VOCs, this paint is considered to be better for the environment.
When it’s dried, the interior latex paint offers durable and flexible paint, which makes them ideal to paint walls and ceilings. A lot of people prefer using water-based paints since it is easy to clean tools, brushes, and spills with just water and soap.
What Are Oil-Based Paints?
When it comes to oil-based paints, they are usually made up of natural oils such as soybean, linseed, synthetic alkyds, or Tung. These paints are known to contain oil resin binder, pigment, and the solvent thinner. When a surface is coated with oil-based paint, the thinner will evaporate, while the pigment and resin will create a durable hard coat.
On the other hand, oil-based paints are considered to be less environmentally friendly since they create more VOCs. Plus, it is harder to clean the surfaces that are coated with this type of paint. Oil-based paints are ideal to be used on doors, baseboards and trims that usually need a more durable paint because these objects tend to get into contact with furniture, vacuums, and human hands.
Oil-based paints take a long time to dry, but you get a tough, hard film on the surface you paint. When it comes to clean up, it can be more difficult since it requires turpentine, paint thinners, or mineral spirits in order to clean tools, brushes, and spills.
2. Additives (Liquids, Solvents, or Fillers)
Latex paints contain water and oil-based paints contain mineral spirits, which are known for spreading the pigment color plus binder on the surface, and then they evaporate. Also, paints come with different additives that have different uses:
- Bonding additives help with the ‘adhering’ ability of the paint.
- Fillers like lime, barite, talc, and clay help with thickening the paint film.
- Texture additives such as fine sand are present to lessen the slippery effect of things like stair runners.
- The enamel makes the paint more durable, harder, and less porous once it has dried.
- Anti-microbial additives or conditioners are added to help improve the flow and reduce brush drag, enhance the paint’s leveling ability, and resist mildew.
- Specific scents are added so that the paint smells better.
- Glitter is added to improve the paint’s reflective properties.
3. Pigments
The paint gets its color with the use of pigments, which can either be inorganic or organic. The pigment used in paint also determines the durability of the color. This shows how often the walls will need to be repainted.
When it comes to organic pigments, they are either made from animal or vegetable origins and tend to be naturally transparent. They aren’t as long-lasting as their inorganic alternatives, but the paint industry is working on changing that through modern chemistry.
On the other hand, inorganic pigments are made up of solid mineral colors, which occur naturally but they have to be modified during paint manufacture. Inorganic pigments have been around for a very long time as they were found on cave paintings that were 30,000 years old. All of the white pigments are known to come from inorganic sources, such as titanium dioxide which is the most common one.
Moreover, organic pigments tend to blend, mix, and disperse towards the base and come with better transparency as compared to the finely ground inorganic compounds, which get blended and suspended within the base. The higher the inorganic particle count, the more solid content there is. Hence, this results in deeper and richer colors.
4. Binders
It is the binders’ job to hold the paint pigment together and form a durable film on the surface. These are plastic-like polymers that help form a stronger bond with the different surfaces. Plus, binders help in creating resistance against abrasion and the standard household cleaners. In the case of latex paints, binders need to be 100% acrylic and not a mixture. In the case of oil paints, it usually contains drying oils like linseed, Tung, or other modified oils.
Can You Use Interior Paint Outside?
Why would anyone want to use interior paint outside? There can be several reasons for that. It is less expensive, the color is nice, there is some paint leftover, and so on. However, it is still not recommended to be used outside.
As compared to exterior paints, interior paints come with a different formulation. Interior paints aren’t made to tolerate extreme changes in outdoor temperatures and conditions such as snow, rain, mildew, and mold. Hence, it will fade, break down, and chalk a lot more quickly. Plus, interior paint tends to be more porous, it cannot properly bind with the exterior surfaces, and can easily flake and crack.
However, if you really want to use interior paint outdoors, then you need to use 1 to 2 coats of an exterior-grade, clear-coat paint sealer. This will help in extending the paint’s longevity, which also depends on how much the paint gets exposed to the outdoor elements. But, the paint will eventually fade, and the sealer might turn yellow.
Furthermore, when you use interior paint with a sealer, this increases the workload, increases the cost, and ends up with a cheaper paint finish. Plus, this cancels the warranty of the interior paint when it’s used outdoors.
When you paint a front door’s inside surface using interior grade paint, this works out because that surface doesn’t get exposed to the outside elements. You will need to properly prepare the surface, especially if it’s made from metal. The same paint can be used on the exterior side of the door if there’s a glass or storm door to protect it, or else, it will chip, crack, and fade.
There’s tons of prep work needed when interior paint is used on interior concrete slabs or walls such as filling the cracks, using a sealer, using TSP for cleaning, using a masonry primer, and multiple coats of paint. But, when you use interior paint on exterior walls, this requires an extra coating of a quality exterior sealer to be used over the interior paint. Also, exposure to outdoor elements will still make the interior paint fade away a lot faster than exterior paints.
Moreover, some people also use interior paint as their exterior primer. However, it should be lightly scuffed using sandpaper to improve its sticking abilities and then coated with a quality exterior paint of a similar base. You might still be required to repaint your surface after a year or two; this depends on the outdoor climate and the paint’s adhesive qualities. Modern interior grade paint is made to be used indoors, not outside.
What To Do If Interior Paint Was Used Outside By Mistake?
Accidents can happen, where you end up using the wrong kind of paint. However, this is not a big deal. You will just be required to repaint your surface in a couple of years instead of ten years.
Interior paints are made to be used indoors as they cannot handle the harsh outdoor temperature and conditions. It will fade a lot faster as well. Hence, you can either repaint using exterior paint or wait to do so for a few years.
If you just started painting, there’s still time to paint over it using exterior paint. But, if you are almost done painting, then just complete the job. People recommend using an expensive sealer over the interior paint if used by mistake. However, it is cheaper to just get a quality exterior paint of the same color and base, and use that instead.
Can Interior Paint Be Used Over Exterior Paint?
There is a massive difference between interior paint and exterior paint since modern chemistry has made these products for their specific uses. You CAN apply interior paint over exterior paint, but why would you want to do that?
There’s a lot of prep work that’s needed before applying the interior paint onto the exterior-painted surface. Plus, the paint won’t be able to handle extreme outdoor temperatures and conditions, as well as exterior paints, do.
You might initially save money with this method, but you would have to repaint your walls again and again, which means spending more money. However, if due to a renovation, the exterior wall is now an interior one, then you can use interior paints on it without worrying about anything.
Conclusion
As mentioned in this article, interior paint is specifically formulated for indoor use, hence it is best to not use it outside. Even though it can be used outside, it won’t last for a long time and you would have to repaint your walls.
Hopefully, this article helped you in differentiating between interior paints and exterior paints. Please leave your comments below if you found this article interesting or helpful.
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