How Long Can Primer Sit Before Painting?

There is no doubt that priming before painting is a critical step, especially if you want your paint to last for a long time. However, you may be wondering how long can you wait to let the primer sit before painting over it?

The answer is dependent on the type of primer you’ll be using. Oil-based primers can last for up to 48 hours before painting, while latex primers should be painted over within 24 hours. If you wait too long to apply paint, the primer may start to degrade and not work as well.

The fact that primers have different drying and cure times, makes them a bit tricky to work with. However, a little know-how can make the process pretty much a success.

Note: If you're not sure how long the primer has been sitting around, it's always best to play it safe and use a fresh batch. This will ensure that your paint job turns out looking its best.

How Long Can Primer Sit Before Painting?

Different Types of Primers and Their Drying Times

Before we dive into the details, let’s first take a look at the different types of primers and their drying times. This information will come in handy when you’re trying to determine how long should you let it sit.

Oil-based primer – They are notoriously slow to dry. In fact, they can take up to 24 hours to dry fully. On the other hand, they are exceptionally resilient and long-lasting once set.
Latex primer – They are much faster in drying than oil-based primers. Within 4-6 hours, they may usually be painted over. However, latex primers are not as durable as oil-based ones and may not last as long.
Shellac primer – It is a type of solvent-based primer that dries very quickly. It can easily be painted over in 15-30 minutes. However, because of their fast drying times, it can be a bit tricky to work with shellac primers.

Note: The drying time of a primer varies with each manufacturer. You can usually find it on the can label or manufacturer's instruction.

What Is the Difference Between Drying, Sit and Cure Time of a Primer?

Now that we know about the different types of primers and their drying times, let’s take a look at the difference between the drying, sitting, and cure time.

Drying time – The amount of time it takes for the primer to dry to the touch.
Sit time – The amount of time you should wait before applying a topcoat.
Cure time – The amount of time it takes for the primer to fully cure and harden.

Factors That Affect the Primer’s Sit Time

Apart from the primer itself, there are some external factors as well that affect the overall sit time of it such as:

Temperature

The temperature has a direct effect on how long it takes for the primer to dry. In general, the warmer the temperature, the faster the primer will dry. However, if it’s too hot, the primer may actually start to evaporate before it has a chance to dry.

Note: The ideal temperature for a primer to sit is between 70-80 degrees Fahrenheit.

Humidity

Humidity is another factor that affects primer’s sit time. In high humidity, it may take longer to dry, that is because the water vapor in the air is competing with the primer for space on the surface.

On the other hand, in low humidity, it may dry too quickly and as a result, it may not have enough time to properly bond with the surface.

Note: The ideal humidity for a primer to sit is between 50-70%.

Type of Surface

The porosity of the surface you’re priming is another critical factor to take into consideration.

For example, if you’re priming a porous surface like wood, it may take longer to dry because the primer has to soak into the pores of the wood. On the other hand, if you’re priming a non-porous surface like metal, it will dry much faster.

Dust & Debris

If there’s a lot of dust or debris on the surface you’re priming, it will take longer for the primer to dry because the particles will be in the way of drying. To ensure that it dries as rapidly as possible, it is advised that you clean the surface before applying it.

Note: Because primer has sticky characteristics, it should not be left sitting for lengthy periods, as it will naturally gather and build up dust, dirt, and stink. You can prevent this by covering the surface with a plastic tarp.

Application

The way you apply the primer can also affect how long it takes for it to dry. For instance, if you apply it too thick, it will take longer to dry because the primer has to cure all the way through. On the other hand, if you apply it too thin, it may not have enough time to properly adhere to the surface.

TIP: Use a spray gun to apply the primer for even coverage and quick drying.

Ventilation

Good ventilation is important when applying a primer because it helps the fumes to dissipate and the primer dry quickly. If you’re working in a small, enclosed space, it’s best to open up some windows or use a fan to help ventilate the area.

Note: Do not use hair dryers, space heaters, or other devices that create heat to try to speed up the drying time of the primer. This can actually cause it to start to cure too quickly and may result in an uneven finish.

How to Fix Common Issues When the Primer Has Sat Too Long?

While you wait for the primer to set, you might encounter some common issues, eventually leading your paint job to be a mess. Fortunately, with proper instructions, you can avoid or fix these issues:

Bubbles on Your Primer Wall

If you see bubbles forming on the surface of the primer, it means that the primer is drying too quickly. To fix this issue, simply use a wet sponge to lightly dab the bubbles. This will help to break them and allow the primer to spread evenly.

Runs & Sags on Your Primer Wall

If the primer begins to run or sag, it indicates that it is too thin. To fix this issue, simply apply another layer of primer to even it out. Before applying a second layer, make sure the first one dries completely for an even finish.

TIP: Apply the primer in vertical instead of horizontal strokes, this will help to prevent runs and sags.

Dust & Debris on Your Primer Wall

If the primer has accumulated dust or you applied it directly without cleaning the wall, it will not adhere to the surface properly. You can fix it by simply sanding the area lightly and reapplying the primer.

TIP: Use soapy water and a sponge to wipe off the dust or grime before applying primer. Or you can also use vacuum cleaners with the hose attachment to suck up any dirt on the surface.

Scratches on Your Primer Wall

Primers can start to scratch before they set because they are still in the process of curing. After the first coat has dried fully, apply a second layer to fix this.

What Happens If You Paint Over Scratched or Ruined Primer?

The answer is obvious, painting over scratched primer will likely give an uneven and unappealing paint job. However, if you accidentally happen to scratch the wall while the primer is still curing, you can sand the area lightly and apply another layer.

On the other hand, if the primer has been damaged or degraded across a big area, there isn’t much that can be done. The best thing to do is to sand the existing layer using grit paper and then start over with a new coat

Note: Avoid painting over an already set primer. This is because it loses its adhesiveness and the new paint will not stick properly and will eventually start to chip and peel off.

When Should You Use a Primer on Your Wall?

As a general rule, you should always use a primer before painting. This is because they help to create a smooth surface that paint can easily adhere to. In addition, they also help to hide imperfections on the wall and provide better coverage. To be precise, use primer when:

Need A Base Coat – A priming coat is required for newly constructed walls or surfaces that have never been painted previously. This is because these surfaces are usually not smooth and have a lot of flaws that need to be covered up.
The Surface Is Uneven – If the wall has cracks and holes, you’ll likely need to seal them before painting them over. In this case, using a primer will help to even out the surface and provide a better finish.
Painting Over A Glossy Surface – When the surface of your wall is glossy or shiny, it’s best to use a primer before painting. Such surfaces are difficult for paint to adhere to. So using a primer will help to create a smooth base for the new paint color.
You Want To Transition To Lighter Color – If you’re painting over a dark color with a light one or vice versa, you’ll need to use a primer. This is because, without it, the new paint color will likely be warped.

How Many Coats of Primer Should You Use?

It depends. If you’re just trying to cover up a light color, then one coat should do the trick. However, if you’re painting over a dark color or an uneven surface, then two coats may be necessary.

As a general rule of thumb, always start with one coat and then go from there. Apply a second layer of primer if you see the fresh paint color getting distorted.

Moreover, the type of primer you choose will determine how many coats you apply. For example:

Water-based primer – one coat should be enough.
Oil-based primer – two coats should be enough.
Latex paint as your topcoat – three coats will be necessary to get good coverage for your project.

What Is The Best Time to Paint Over Primer?

Ideally, you should wait until the primer is completely dry before painting over it. This usually takes about 24 hours. However, if you’re in a rush and need to paint sooner, you can try to wait at least 6-8 hours for it to set.

Note: Make sure to check the manufacturer's instructions to see how long you should wait before painting.

Alternatively, you can also use primers that dry quickly so that you don’t have to wait as long. These are often labeled as “quick-drying” or “fast-drying” primers.

If you’re still unsure, it’s always best to err on the side of caution and give it more time to dry. This is because if you paint over primer that isn’t completely dry, the new paint job will likely be ruined.

How Do You Make Primer Dry Faster?

If you’re in a hurry and need the primer to dry faster, there are a few things you can do such as:

Try high-quality solvent-based primer – This type will dry faster than others.
Use a fan – Place the fan about 3 feet away from the surface and turn it on to the high setting.
Place a dehumidifier – This will help to remove moisture from the air, which will in turn make the primer dry faster.
Create a cross breeze – Open the windows on opposite sides of the room to create a cross breeze.

How Long Does Primer Take to Dry?

The time it takes for the primer to dry varies based on the type being used, as well as the room’s temperature and humidity.

As a general rule of thumb, water-based primers will take about 30 minutes to an hour while Oil-based primers will take about 6 to 8 hours to dry.

Let’s describe each type and drying time more in detail.

Latex Primer

Acrylic polymer is used to make this sort of primer. It’s water-based and simple to apply. It may be applied on wood, metal, and plaster, among other surfaces.

Generally, at room temperature, the latex-based primer will take about 30 minutes to an hour to dry. However, if the humidity levels are too high, it can take up to 24 hours.

Oil-Based Primer

This type is produced from petroleum-based materials and dries to a tough, long-lasting finish. It is ideal for use on surfaces that are prone to stains or mildew, such as kitchen cabinets, bathrooms, and laundry rooms.

Oil-based primer will take about 6 to 8 hours to dry at room temperature. However, if the humidity levels are too high, it can take as well up to 24 hours.

Shellac Primer

It is composed of lacquer and denatured alcohol. Shellac primer dries very quickly, making it ideal for use in high-traffic areas or when you need to paint over stained surfaces. Generally, this type will take about 30 minutes to an hour to dry on surfaces such as wood, metal, and plastic.