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Can You Use Interior Stain Outside? (Quick Answers)

Our homes are one of our most valued possession. It is a place of comfort where many of us spend most of our time whereas others return to find comfort and relaxation. 

So it is in our best interest to keep it in good shape – and you will find information to do just that down below.

Can you use interior stains outside?

Interior stains are not formulated the same way exterior stains are and therefore they lack vital chemicals such as UV absorbers, mold retardants and therefore will not be effective and last as long as exterior stains. However, you can use interior stains on surfaces with less sunlight exposure.

Both interior and exterior stains are used to protect wooden items and furniture at our homes or offices but the items and furniture both indoors and outdoors face different impacts from various factors such as sunlight exposure, wind, temperature variation, etc.

This is why both surfaces require different variants of protection and stains to be durable against different factors. 

Interior wood stain:

Interior stains are used for finishing furniture and on several woodworks such as interior doors, window frames, shelves, etc. 

These stains are usually packed with chemicals to protect against moisture, scratches, or any other solvents while making the surface shiny.

Interior oil-based stain: 

There are commonly two types of interior stains: Water-based Interior wood stain and Oil-based interior wood stain. Water-based interior wood stains use water as the base solvent which is thinned up and cleaned with water. 

They are much easier to clean than oil-based stains but expensive to buy.

In contrast, oil-based stains such as Minwax interior stains are very popular and are the most commonly used among the two types of stains. Besides their stain, they have color pigments in them dissolved in the oil as a base. 

Oiled-based stains are much easier to use compared to water-based stains but not as environmentally friendly.

On the other hand, exterior stains are used on outer doors, decks, railings, patio furniture, or any other structures used outdoors. 

What makes them different from interior stains is that these exterior stains come packed with chemicals that make the outdoor wooden structures more suited to handling adverse conditions. 

The stains contain UV absorbers, mold retardants, scuff resistors, fade resistors, and sometimes insect repellents as well.

Will interior stain work outside?

Interior stains and exterior stains are manufactured with different chemicals and compositions because of the different requirements both stains need to meet on these different surfaces indoors and outdoors. 

Using the stains interchangeably will not give the satisfactory performance that you would generally expect.

However, many people do not wish to spend more money on different stains and instead use their interior stains to coat wooden structures both indoors and outdoors. Although they can use the indoor stain outside, their effectiveness will be nowhere near an exterior stain.

Exterior stains contain chemicals such as UV absorbers, mold retardants, and many more which makes the outdoor wooden structures more durable against harsh environmental conditions which interior stains cannot offer. 

Interior stains can work outside only if they are applied on surfaces that aren’t exposed to sunlight and if the stain is reapplied frequently.

What happens if you use interior stains outdoors?

Using indoor stains outdoors might be a budget-friendly move but in the long run, it could bring avoidable consequences on your outdoor wooden structures. Some of the common problems after using indoor stains outdoors are listed below:

Fades away when exposed to sunlight:

Exterior stains are manufactured with chemicals such as UV absorbers that protect wooden surfaces against damaging UV rays from sunlight. 

However, interior furniture or wooden structures are not exposed to the sunlight and so interior stain manufacturers do not include UV absorbers or similar chemicals in them.

If you use interior stains outdoors, you will notice how quickly the stain fades away if the surface is exposed to sunlight. Not only that the stain will fade away faster, but it also fails to protect the surface against UV as effectively as exterior stains.

Vulnerable to molds and fungus:

Molds and fungi thrive in places where they find a good balance of warmth and moisture. And wooden structures outdoors are one of the perfect hosting spots for molds and fungi since wood can absorb and retain moisture.

This is why most exterior stains include mold or fungus retardants while interior stains don’t. Therefore, using interior stains outdoors will not protect outdoor wooden structures against mold or fungus infestation.

What is the difference between interior and exterior stains?

Interior stains and exterior stains are manufactured much differently because both stains are applied to different locations where they face different temperatures, humidity, and other external factors. 

This is why both of them have to meet very different requirements and protect surfaces against different kinds of threats.

Which surfaces to apply on:

As the name suggests, interior and exterior stains are to be applied in different settings – indoors and outdoors. And so the furniture or wooden structures on both locations vary as well and both stains are designed for those specific types of furniture as well.

Interior stains are mostly applied indoors on interior woodwork such as doors, windows and door frames, furniture, and other indoor wooden structures. 

However, exterior stains are generally used on wooden structures located outside such as decks, rails, patio furniture, shutters, etc.

Chemical composition and ingredients:

Since the location where the stains are applied aren’t the same, the environmental factors also vary drastically such as temperature, humidity as well as UV exposure. 

Wooden structures outdoors experience much intense temperature differences, higher humidity, and harsh UV rays from sunlight.

Meanwhile, surfaces indoors do not face such drastic environmental effects and so manufacturers leave out chemicals such as UV absorbers and mold retardants from interior stains. But exterior stains are packed with these chemicals and thus are much stronger.

Impact on the surface appearance:

Exterior stains are commonly known to contain color pigments in them which not only protects the outdoor surfaces but also darkens their surface color. So exterior stains can serve two functions in one. 

Whereas interior stains do not contain color pigments but they do make the surface shiny and clear.

Can interior stain be used outside if sealed by polyacrylic?

Polyacrylic is a water-based finish that is highly water tolerant and is used on top of stains to protect it from moisture and high humidity. It can be applied outdoors with a spray or rollers to provide protection to wooden surfaces.

If someone uses interior stains outdoors, the surface is mostly exposed to two major threats that are UV light and moisture. Exterior stains are equipped with chemicals to protect the surface against both UV light and moisture but interior stains aren’t.

Therefore if the interior stain is used outside and sealed by polyacrylic, it will only protect the stain against moisture but not UV lights. So interior stains can only be used outside in places where sunlight does not reach.

How to use interior stains outside?

It is highly advised to not use interior stains outside and instead use specific exterior stains because they are manufactured with chemicals to protect wooden surfaces outdoors better. But if you wish to use your existing interior stains outside, here’s how you can do it:

Pick the suitable area of application:

Interior stains cannot be used in all areas outside because of their vulnerability against UV light and the stain fades away quickly in their exposure. Therefore, you should apply the stain to locations where very little sunlight reaches or in any locations that receive a lot of shadows.

Clean the surface:

Once you have picked the location and the structure you want to stain, clean it with a dry and clean piece of cloth or paper towel. You can also use clothes or paper wet with rubbing alcohol to clean off the surface.

Apply the interior stain in multiple layers:

After the surface has been thoroughly cleaned, apply a layer of interior stain on the surface and let it dry. Follow up the layer with more layers on top but make sure to give enough time for each layer to dry.

Coat the stain with a polyacrylic finish:

When you have applied several layers of the stain and they have dried, finally use the polyacrylic finish over the stained surface using either a sprayer or using a roller. You may wish to apply a thick or thin layer of the polyacrylic finish based on how humid your area is.

Final Thoughts

Interior stains are not manufactured in the same manner as exterior stains are, and as a result, they lack important chemicals including UV absorbers and mold retardants, making them less effective and durable. But Interior stains can be used on surfaces that receive less sunlight.