Can You Mix Interior and Exterior Paint?

So, you’ve been painting your wall, and everything seems to be going fine when suddenly you hit a dead end – you realize the paint can is empty. Then you remember you have some leftover paint in your storage room. 

An idea pops into your head – since it’s the same color, why not mix the paints? But it is exterior paint, so you’re wondering if it’s OK to mix interior and exterior paint. We have the answers. 

In this article, we will explore the difference between interior and exterior paint and what happens when you try mixing the two.  

What Is Interior/Exterior Paint?

Paint is often classified into two broad categories – interior and exterior paint. As their names suggest, interior paint is meant to be used inside the house, while exterior paint is meant to be used outside. 

In other words, interior paint is intended for areas within the house, such as your living room, bedroom, kitchen, bathroom, hallway, etc. The main highlights are good coverage and little-to-no VOCs or harmful chemicals. 

Most interior paints are water-based, which makes them safer. They are also easy to clean, depending on the type of finish. 

Exterior paints, on the other hand, are meant to go outdoors. As a result, they are made to withstand harsh environmental conditions such as sunlight, rain, and mildew. They usually contain more resin and additives, which provide additional durability. 

Unlike interior paint, exterior paint is predominantly oil-based and is characterized by a high level of VOC. 

What Is the Difference Between Interior and Exterior Paint?

Understanding the difference between interior and exterior paint will help you know when to use them. Here are five main differences between interior and exterior paint.

1. Hardness

Interior and exterior paint are made with different resins, which determine their hardness. The resins used in exterior paint are usually more flexible and can expand or contract when there’s a change in temperature. 

Interior paints, on the other hand, contain more rigid resins and dry harder than exterior paint. While this makes them more scrubbable (easy to clean) and resistant to scratches, they cannot withstand huge temperature changes. 

To put it more simply, interior paints dry harder than exterior paint and do not expand or contract with changes in temperature.

2. Weather protection

Besides hardness, the resins and additives used in paint also determine where it can be used. In interior paint, the emphasis is on stain resistance and something that is easy to clean. However, in exterior paint, the focus is on something that can withstand harsh weather conditions. 

This is why most exterior paints are often labeled with terms like “UV-resistant,” “mildew-resistant,” and “water-resistant.” Interior paint does not usually have these properties and will fade and flake quickly when used outside.

3. VOCs

Another important distinction between interior and exterior paint is the VOC level. 

VOCs (or volatile organic compounds) are chemicals that keep the paint in liquid form. They are released into the air when you apply the paint. Unfortunately, these chemicals are toxic and can cause respiratory issues, especially when you expose yourself to them for long. 

Interior paints typically have low or no VOC emission. In contrast, exterior paints emit a significant amount of VOCs, which makes them very unsafe to use indoors.

4. Color and styles

Both exterior and interior paints offer different color options to choose from. However, interior paints usually have a wider color selection and styles. 

So, you will find interior paints in satin, matte, semi-gloss, and other finishes. However, most exterior paints are limited to flat or gloss finishes.

Likewise, while exterior paints are predominantly oil-based, most interior paints are water-based or latex. 

What Types of Paint Can Be Mixed Together?

While it’s possible to mix interior and exterior paint, this cannot be done with all paint. In this section, we look at the different types of paint that can be mixed together.

Can you Mix Different Paint Brands?

Yes, it’s possible to mix paints from different brands, but this is more likely to work if it’s the same type of paint. For instance, let’s say both paints are acrylic but are different brands; you can mix them. 

Notwithstanding, since both paints are different brands, their formulations are different even though they are the same type of paint. So, beware, sometimes the two paints might not mix. 

Having said that, you will never know until you try. As long as it’s the same type of paint, the likelihood of mixing them is usually higher. 

Can You Mix Paints With Different Finishes?

There are different types of paint finishes; the more popular ones are matte, eggshell, satin, semi-gloss, and high-gloss. Each of these has a different level of sheen or reflectiveness. 

While it’s possible to mix two different finishes, the resulting paint will have a reduced gloss. In other words, the mixed paint will appear duller. 

For example, let’s say you mix a satin and high-gloss paint. The resulting paint will no longer be as shiny as the high-gloss paint. 

Can You Mix Water Based Paint and Oil Based Paint?

No, you can’t mix oil-based and water-based paints. These are two different bases. Even if the paints are the same color or finish, they won’t mix. And that is because oil and water don’t mix.

If you need to mix two different paints, they must have the same base. In other words, oil-based paint can only be mixed with oil-based paint, while water-based paint can only be mixed with water-based paint. 

Examples of oil-based paints that you can mix include enamel, varnish, and alkyd. On the other hand, you can mix Latex and acrylic paints to your desired outcome because they are both water-based. 

Can You Mix Latex and Enamel Paints?

No, you can’t. Latex and enamel are two different types of paint designed for different purposes. So, you need to understand your project to determine which one is better between Latex and Enamel paint.

Latex is water-based and is commonly used inside the home to paint walls and ceilings. Enamel paint, on the other hand, is oil-based and is commonly used on metal surfaces. 

Since these (oil and water) have different properties, it’s not recommended to mix both paints. 

You might be able to succeed if you’re working with acrylic enamel paint. But you may have to deal with poor adhesion and a paint job that is not durable. Also, the color will not be inconsistent, and you will have a hard time applying the paint. 

Can You Mix Two Different Brands of Latex Paint Together?

If you have two brands of latex paint, you might be able to mix them, but there’s no guarantee the final product will be great. Even though they are both latex paints, they are not formulated in the same way since they’re from different companies. To increase your chances of getting a smooth blend, use two paints from the same brand. 

What to Consider When Mixing Interior and Exterior Paint

If you do decide to mix interior and exterior paint, here are the main things to consider:

1. Paint Base 

As we mentioned earlier, paints are classified into two broad categories depending on the base solvent. Oil-based paint has oil as the base, while water-based paint has water as the solvent. 

Since water and oil do not mix, you cannot mix oil- with water-based paint; otherwise, you will get an uneven, dull color. If you must mix two paints, they must have the same base. In other words, both the interior and exterior paint should be oil-based or water-based. 

This also applies to the paint type. For instance, with latex paint, you may ask – can you mix interior and exterior latex paint? Well, you can!

2. Paint Brand

Another thing you should consider is the paint brand. You have a better chance of getting results when you mix two paints from the same brand. 

In contrast, if you’re using paints from different brands, there’s a huge chance they don’t mix evenly, even if they have the same base. The reason is simple – different paint brands use different formulations for their paint. 

In other words, the composition with regard to binders, pigments, and additives are not the same. So, getting them to mix is never guaranteed, even if it’s the same type of paint. 

3. Glossiness

In addition to the paint base, you should also consider the gloss levels of the paint you plan to mix. This is particularly important if you’re trying to achieve a certain look or effect. 

Mixing paint with different sheens can result in streaks or uneven coloration. Your best bet is to use paints of equal gloss level or at least close. 

4. Location

Another thing you need to decide on when mixing interior and exterior paint is where you want to use it. If you plan to use the mixed paint indoors, then you will need to worry about the paint’s VOC count. In this case, it’s recommended to use less exterior paint and more indoor paint. 

On the other hand, if you plan to use the paint outdoors, you will be more concerned about durability. In this case, using more exterior paint in the mixture will be favorable.

5. Color

You should also be mindful of the paint colors. Except you’re sure of the outcome, do not blend paints of different colors. At best, you want to stick with paints that are of the same type and color. This is why it’s always a good idea to test things out before committing to a large pour. 

How to Mix Interior and Exterior Paint

As earlier indicated, we won’t recommend mixing exterior and interior paint. But just in case there’s some leftover paint you wish to mix with your interior or exterior paint, this section will offer some advice on how to go about it to minimize potential issues and get some results.

To have any success with this method, the paints to be mixed must have the same base. You don’t want to mix a water-based paint with an oil-based paint. 

What You Need

Besides the paints to be mixed, you will need a separate bucket and something to stir the paint (i.e., if you’re not using any fancy equipment to mix the paint). The bucket should be big enough to accommodate the paints, with plenty of space for easy movement and stirring. 

Step 1: Mix The Paints

The first step is to mix the two paints. Pour the first paint into a large bucket, followed by the second paint. It’s best to use an exact ratio, especially if you’re trying to achieve a certain level of gloss. Otherwise, if you mix the paint in any proportion, you might not be satisfied with the appearance, especially if they are different finishes. 

To make future projects easier, it’s a good idea to record the amounts used.  

NB: To maintain harmony, the paints you’re mixing should be of the same color.

Step 2: Stir the Paint

Next, you want to stir the paint with a paint stirrer or stir stick. Stir for at least 2-3 minutes or until you get the colors to completely mix. Ensure you scrap the bottom and sides of the bucket so you don’t leave out anything. 

If you don’t want to manually stir the paint, you can use a drill attachment. This might work better, but you need to know how to operate it.

Step 3: Test the Color

Once you’ve mixed the paint, you want to test it on a small, inconspicuous area before using it on the main project. This way, you can evaluate the final color and determine if it’s what you want. If you’re not satisfied with the result, you can continue mixing until you get the color you want.

What are the Effects of Mixing Interior and Exterior Paint

Here are some of the effects of mixing interior and exterior paint:

1. Health Implication

One of the main problems of mixing interior and exterior paint for indoor use is the resulting VOC. Interior paints typically have low or no VOCs. However, by mixing them with exterior paints (which usually have high VOCs), you will increase the VOC component. 

Using the mixed paint indoors can pose a health hazard, which can put you and your loved ones at risk of several respiratory problems, as

2. Quality 

As earlier indicated, interior and exterior paint have different compositions, each with unique pigments, resins, and additives. So, when you mix both paints, there’s a huge chance the overall quality will be compromised. This often leads to a poorer finish than you would normally get using the paints separately. 

In worse cases, the mixed paint will not adhere well to surfaces, leading to cracking, peeling, and other side effects.

3. Gloss level

Another effect you might encounter when mixing interior and exterior paint is change in the gloss level or inconsistent appearance. This is more common if the paints you’re mixing have different gloss levels and textures. In this case, you may end up with streaks or clumps on the paint job. 

Even when the gloss level of both paints are the same or close, nothing is guaranteed since the paints have different compositions.

4. Performance 

While exterior paint is designed to withstand rain, UV rays, and other harsh elements, interior paint is targeted towards a controlled environment. So, mixing both paints will reduce the performance if you intend to use it outdoors. 

In other words, the mixed paint will be less durable than the original outdoor paint, making it more susceptible to cracking, fading, and mildew attack when used on exterior surfaces. 

One way to get around this is to waterproof the mixed paint by adding waterproofing additives. But this can only work if the additive is compatible with the paint. 

FAQ – Can You Mix Exterior and Interior Paint

What happens if you mix exterior and interior paint?

The main issue with mixing paints is that it often results in poor finishes since both paints have different compositions. Also, because interior paint has lower VOC count, mixing it with exterior paint increases its VOC level, making it no longer safe for indoor use.

Is Exterior Paint More Durable than Interior?

Since exterior paint is designed to withstand harsh conditions outside, it usually provides additional durability than interior paint. Having said that, interior paints possess a higher degree of hardness, which makes them more resistant to scuffing.

Can You Use Interior Paints Outdoors?

While it’s possible to use interior paint outdoors, this is not recommended. This is because interior paint is not formulated to withstand the harsh weather conditions outside. So, when you use it in such an environment, it won’t last long.

Can I Use Exterior Paint Inside?

This is not recommended as it can pose a serious risk to your health. The level of VOC in exterior paint is generally higher in exterior paint. As a result, they can be toxic to your health, especially when inhaled. Also, the strong chemical smell from the paint can be unbearable. So, DON’T use exterior paint indoors.

How long will interior paint last outside?

Interior paint has a short lifespan outside, and that is mainly because it’s not made to withstand the harsh conditions outside. The exact timeframe will depend on how exposure it gets and your local weather. At best, it can last a year or two before it needs to be repainted.

Is it OK to paint interior walls with exterior paint

No, it’s not. Due to the high level of VOCs in exterior paint, using it to paint your walls can be harmful to your health, especially when exposed to it for long periods. Not to mention that exterior paint contains resins that are not suitable for interior surfaces.

Content Summary – Can You Mix Interior and Exterior Paint

To conclude, it is not advisable to mix interior and exterior paint. 

Exterior paints are predominantly oil-based, so they don’t mix well with water-based interior paints. Likewise, exterior paints have significantly higher amounts of VOCs than interior paint, so adding them to interior paint increases the VOC count, making them unsafe for indoor use. 

Finally, interior paints are not designed to withstand the harsh temperature changes and weather outside. So, mixing them with exterior paint reduces their durability and makes them less suitable for outdoor use. 

Instead of trying to mix interior and exterior paints, it’s better to purchase a new can for your project.