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How Long Does Paint Last If Opened? (Explained)

Do you have a can of paint that has been sitting around open for a while? Understandably, you would want to make use of the old paint and brush your walls with what you have.

However, before you do so, you would need to ensure that the paint can be used after all.

How long does paint last if opened?

Once opened, a can of paint can last for an average of two years. However, this timeframe would largely vary and can be as long as 5 years if the paint has been stored properly. Paint that has been opened but sealed in the right way, and kept away from heat, air, and moisture keeps well for longer.

Overall the storage process defines the time of the paint to stay good. But not all paint stays good for the same time period. Let’s get to know about the different types of paints.

Emulsion paint:

In the case of emulsion paint, how long before it goes bad would largely depend on the quality and way of storing it.

Once opened, the emulsion paint can be used within 6 months if it cannot be subjected to too much heat or water exposure.

Wall paint:

Wall paint can be both oils-based and water based.

Regardless of what type of wall paint it is, if the can have been opened, the paint can only be used for up to two years.

The timeframe would be shorter if the paint went through high temperature changes.

Gloss paint:

Although gloss paints used to be oil based before, now they are water based and have better resistance to heat and water.

An opened can, if sealed properly can be used for 2 to 3 years. Gloss paints are hence regularly used in kitchens and bathrooms.

Acrylic paint:

Acrylic paint, when unopened can last up to 10 or 15 years without going bad. Acrylic paint can hold on to its consistency and quality pretty well even after it has been opened for about 2 to 5 years.

If the paint goes through freezing and moisture exposure, it would not last as long before it starts to smell found and lose its smooth consistency.

Dulux paint:

Dulux paints do not have the longest expiry dates and maybe good to be used from 6 months to 2 years after opening.

The time frame would depend on the quality of the paint and if it has been stored in the right conditions.

Latex paint:

Latex paint, similar to acrylic paint is a water-based paint that usually has a shelf life of 2 years after being opened.

If the paint is not kept in a cool room, away from too much heat or moisture, the paint could go bad within months.

Water-based paint:

Although the shelf life of water-based paints is 10 years, the paint would be good to be put on the walls for 2 to 3 years if stored correctly.

Does paint go bad if opened? Does paint expire if opened?

Most paints, whether they are water based or oil-based, have a long lifespan when unopened. Any oil-based paint can be used for 2 to 15 years if not opened. On the other hand, water-based ones can be used for up to 10 years when unopened.

However, when the paint is opened, it slowly gets exposed to moisture and air. Whenever moisture and air enter a paint’s composition starts to change.

Although the paint goes not go bad immediately, its composition is bound to be altered. As bacteria forms, the paint will eventually go bad in the coming years.

Nevertheless, this does not mean paint expires if opened. When sealed properly and kept away from too much heat or exposure to moisture, paint can last many years.

What causes paint to go bad?

There are several reasons why the paint goes bad. Check below to know about them.

Air and moisture:

The entry of air and moisture into the paint is the primary reason a paint can go bad upon opening. When air and water infiltrate paint, the reaction produces microorganisms.

The bacteria form and eat up paint inside. The gaps cause gas to form and hence paint can go warp when opened.

The bacteria are also responsible for the foul smell that can be quite strong as humidity and microorganisms keep on festering.

High temperatures:

Sealing a paint can after opening is not always enough to keep the paint fresh for years.

Another factor that determines how long a paint might last after opening is the temperature it has been stored in.

Varying temperatures and repeated freezing can cause paint to break down completely.

Improper storage:

Water-based paints like latex can last for years and can be used like new paint only if it has been stored properly.

Hence, once the paint is opened, the method of storing is what would determine if the paint would go bad and for how long.

Quality of paint:

Quality of paint can be a contributing factor when it comes to the reasoning of paint going bad.

Good brands do not mix water in oil-based paints and vice versa. If infiltrated if other contents, the paint will go bad quicker than expected.

How can you tell if the paint is bad?

Now, nobody would want to paint their house walls with what has gone bad. If you see a can of paint lying around and plan on using it on your walls, you may want to look for a few signs first.

Here are a few signs that would tell you whether a paint has gone bad:

Bulging paint can:

If you have a can of paint that is unopened or even partially opened, the first sign to look out for is a bulging can.

This happens due to the buildup of bacteria eating paints. Once those microorganisms from inside, gas from the can escape creating pressure. As a result, you can notice a change in the can’s shape.

Strong, unpleasant smell:

We all love the smell of good paint, at least most of us do. When paint goes bad, you would notice how the smell transforms into one that is both sour and unpleasant.

That strong odor is a signal that you’d want to discard the paint. This smell can be quite strong initially, although it fades away slowly.

Lumpy consistency:

Although the smell could be telling enough whether the paint has expired, the consistency of the paint would assure the test.

Upon stirring, if you think that the paint feels lumpy on the mixer, the paint has gone bad.

Moreover, the paint would not have a smooth liquid texture. Instead, bad paints are gloopy and may have solid or gel portions that would stick to the paintbrush.

Can you use paint that has been sitting for a while?

Whether you can use old paint would depend on the condition of the paint. If the paint has been sitting with its lid opened, the exposure to air and moisture is most likely to change the chemical composition of the paint.

However, if you smell the paint and are not fazed by the lurking smell, it could mean the paint is still usable. Other than that, if the paint is smooth upon vigorous stirring, you can still use that paint. You would need to make sure that the paint has not gone all bad.

This is because when the paint is spoilt due to heat, air, or moisture exposure, the smell they give off can be harmful to humans.

The risk of using old paint is that the chemical composition of the paint does not remain the same if it has been unused for a while when the lid has been opened.

How do you make old paint usable again?

Here are a few ways to help you save on new paint and use the old one again:

Add water:

The first trick you could try if your paint has become lumpy is to add water.

This would particularly work on a paint that is either acrylic or latex since these paints have a good amount of water composition. You need to make sure that you add water gradually and not all at once.

Stir properly:

Each time you add a little bit of water, you would need to stir it properly.

 If you think the paint is still gloopy in consistency, stir more vigorously as you add water until the pain feels smooth on the brush.

Add thinner:

If your paint is oil-based, you can add thinner or mineral spirits instead of water. Vigorous stirring is key no matter which solvent you are adding.

Final Thoughts

Opened paint cans last a much shorter time like 2 years than unopened ones. When a paint can is opened, it is exposed to air and moisture. This in turn produces bacteria that causes paint to go bad eventually. You can detect bad paint through its lumpy consistency and foul smells.