Now that winter is starting to wrap up across the country, DIYers everywhere are all beginning to look to our lists of outside projects. Garden and yard tweaks and upgrades, outdoor patio and grilling zone tweaks, curb appeal, etc.; it’s the start of outside season!
One of the most tried-and-true methods to update a space is to freshen it up with new paint. Whether you’re leaning towards a trending seasonal tone or simply refreshing a classic one, paint makes a huge difference! From your deck to your garden furniture to your house itself, paint makes it pop.
So picture this: You have a bunch of leftover interior paint from the indoor projects you’ve been working on throughout the winter. You love the tone and want to keep your color scheme consistent indoors and out. You think, “why buy new exterior paint when I already have all this?.”
In some cases, you can use interior paint outside without much issue (like on a coffee table on a screen-in porch). However, paint manufacturers sell interior and exterior paint for a reason- they’re two different and distinct things. Let’s dive into the similarities and differences and whether or not you can use that leftover bedroom dresser paint on your outdoor chaise lounge!
All Paints Contain…
All paints commonly used around the household share four main components: pigments, solvents, additives, and resins.
Pigments – These fine particles give a paint its color. They can be made from plant, mineral, or animal bypoducts, or even synthetically produced.
Solvents – Solvents are, essentially, the chemicals that keep the paint in a solution. They dissolve and combine the other ingredients into a liquid and then evaporate from the painted surface as the paint dries. For acrylic and latex paints (the majority of the market), that solvent is water. For oil-based paints (more popular outdoors or for metal applications), the solvent is turpentine or mineral spirits.
Additives – Additives are what they sound like- compounds that are added to the paint to offer specific features that improve its performance or finished quality. This could be for the paint’s finish (matte, satin, glossy), drying time, thickness, or, in the case of most exterior paints, fungicides and anti-microbial solutions.
Resins – The resins in paint make it stick to the intended surface. They hold the pigments together and help form the layer the paint creates. These can be more rigid or more elastic, depending on the paint’s intended purpose.
Interior Paint Distinctions
Interior paint uses these four components to make up a product that is overall more resilient to daily impacts. It uses stronger, more rigid resins that resist scuffs and make it easier to scrub or wipe clean, and comes in a variety of finishes (flat/matte, eggshell, satin, semi gloss, glossy). Because interior paints are primarily water-based, they dry quickly, usually within a few hours.
There are also fewer VOCs (volatile organic compounds) in interior paint, making it less stinky during the application process and thus safer for indoor use.
Interior paint also rarely has fungicide additives, though it’s not unheard of! Kilz, for example, is a commonly sold interior-application paint used to seal indoor surfaces that have been treated for mild and mildew, or have been exposed to significant odors like smoke. Because interior paint is more porous than exterior paint, strong smells or microbial organisms can get locked in or thrive in and on the paint if left untreated.
Exterior Paint Distinctions
Exterior paint, on the other hand, is formulated to resist the impacts of weather and temperature fluctuations. Unlike interior paint, exterior paint will withstand freeze, thaw, snow, rain, and sun.
Its additives are targeted for mold and mildew resistance as well as UV protection and fade resistance. The resins are more flexible (since temperature fluctuations cause expansion and contraction), but exterior paint manufacturers typically offer fewer finishes.
The VOCs are higher for exterior paints (which isn’t as impactful since they’re applied outdoors), and some exterior oil-based paints can take up to a week to cure.
Can You Mix Interior and Exterior Paint?
While of course it’s always best to use a product for its intended purpose (and we don’t recommend reinventing the wheel here), there will occasionally be circumstances that point you towards a grey/middle area.
Perhaps your worksite is remote, and you can’t just pop into a hardware store for new paint, or you’re working on a project where there is a minimal budget and all materials were donated (a school, nonprofit, etc.).
In this case, it is possible to mix interior and exterior paints, given a few guidelines and cautions:
- As we all know, oil and water don’t mix. If your interior paint is water-based and your exterior paint is oil-based, it will make a big stinky mess, and you’ll only end up with a larger amount of unusable paint.
- Be aware of tint. Elementary school taught us that mixing too many colors together ultimately gets you a weird brown shade, and that hasn’t changed. The pigments of your paint should be strongly considered before you mix them together.
- Mixing paints with different finishes won’t ruin your paint, but it will diminish its significance. For example, if the color code is the same but you are mixing a high-gloss exterior paint with a matte interior paint, the resulting mixture will have significantly less sheen (depending on the percentage of the mix).
- You can mix different brands as long as they have the same solvent, but this would definitely void any warranty offered by either manufacturer.
- You won’t have the same strengths of either when one is essentially diluted by the other by mixing. Exterior paint will be less mildew and weather resistant if mixed with interior paint and used outdoors, and interior paint may lose some impact resistance if mixed with exterior paint and used indoors.
Can You Turn Interior Paint into Exterior Paint?
“Turning” one kind of paint into another isn’t really an exact term for the process. Unlike transforming a human in a vampire or a caterpillar into a butterfly, “turning” interior paint into exterior paint is more about simply augmenting the paint’s additives to make it more effective in an exterior application.
Though there is no industry-standard hard-and-solid recipe to turn interior paint into exterior paint, the following suggestions are generally agreed upon, should you decide to give this a shot:
- Interior paint lacks fungicides, so you’ll want to add a mildewcide like M-1 to the paint, following the manufacturer’s specifications for the amount.
- Interior paint lacks exterior paint’s weathersealing properties, so adding a few ounces of water-based polycrylic to the paint will help towards a watertight seal.
- Finally, mixing in some paintable, exterior-grade caulk will help with the flexibility and adherence of the paint. Some exterior-grade caulks include anti-microbial agents as well, so choosing one with that feature would add to the overall strength and resilience of the paint.
Now, supplementing your interior paint in this way will make it more effective outdoors. However, because this is a very inexact method, exterior paint straight from the manufacturer will always be best.
Augmented interior paint will likely peel or chip sooner, fade sooner, and adhere less strongly in outdoor environments. If you already have these additives on-hand, it may be an easy and quick short-term solution. However, after purchasing these 3 additions, you may end up spending almost as much as a new gallon of exterior paint would have cost in the first place.
So- can you use your dresser paint on your exterior chaise? Overall- the cautionary answer is yes- but just don’t expect the same results!