Does Kilz Go Bad? – How to Make Your Primer Last

Can you still use that leftover Kilz primer sitting in your garage from your last paint job? Perhaps it’s giving off a weird smell, or it’s just been a long time since you’ve used it, and you’re not sure if it’ll work well anymore.

Unfortunately, Kilz primers may expire or decay. The presence of impurities and the manner of storage can speed up the decay process. It’s especially imperative to avoid extreme temperatures since hot and cold can ruin the product.

Mildew or mold will grow on latex paints stored in a warm environment, while temperatures that are too cold can cause the oil to separate in oil-based paints. 

This article will explain how these primers go bad and what you can do to keep your leftover paints and primers in good condition.

painting residential home

Do Kilz Products Have an Expiration Date? 

Like all products, Kilz paints have a lifespan that can vary based on the conditions you store them in.

According to the manufacturer, unopened paints and primers have a shelf-life of less than two years. However, it’s hard to predict the shelf-life after opening or using the primer. You can probably expect a shelf-life of six months after opening the product. 

Can Kilz Primer Go Bad?

There are several signs that can indicate that a primer has gone bad.

A common sign is a rotten egg stench. You’ll smell this immediately when you open the latex primer after not using it for a long time. Beyond the bad smell, you can also look for thick clumps, a thin mildew film, or separated components.

Thick clumps or a thin film of mildew can be challenging to dissolve. If you notice thickened paint particles and mildew in your primer, get a replacement. 

You may also notice that certain components have separated if your primer has expired. Expired oil-based primers will have a layer of oil floating above the other ingredients.

In this case, try mixing vigorously to see if the primer returns to its original state. Safely discard the primer if the constituents separate again. 

Is Kilz Primer Supposed to Be Watery?

Yes, it’s normal for Kilz primers to be thin and watery. According to most users, recent batches of Kilz primers are thinner and more watery than old batches. It may be the result of a new formula. 

Nevertheless, this new formula is just as effective as the previous one. You can stir the primer to thicken it to your desired consistency. 

Does Freezing Ruin Kilz Primers? 

A common mistake is storing leftover or unused primers in garages without temperature control. Latex-based primers will quickly freeze when the temperature drops to 10°C or 50°F. However, oil-based paints will freeze at a lower temperature (-20°C or -4°F). 

In most cases, freezing and thawing will ruin the primer. The primer’s components will often separate and form little clumps upon thawing. The best solution is to gradually warm up the primer to room temperature. Then, stir it until the consistency becomes smooth. 

Sometimes, you don’t get lucky and may end up with a ruined primer. In that case, you’ll have to invest in a replacement.

How to Stop Kilz Primer from Expiring

painting a wall using Kilz Primer

You can’t avoid the inevitable. But you can increase the longevity of your primer by following the proper steps.

When priming that indoor or outdoor surface, follow these guidelines to prolong the lifespan of the primer:

  • Reduce the number of times you open the primer container. Exposure to air may cause it to thicken, especially when the primer has a high drying rate. So don’t leave it open while painting. It’s better to pour the needed quantity into another container. 
  • Don’t overstir the Kilz primer. This is to avoid letting too much air into the product. Remember to remove the stirring stick and close the lid. 
  • Clean the edge of the can that comes in contact with the lid. You can use a polythene wrap or shower cap to cover the primer during painting. 
  • Don’t dip your paintbrush directly into the paint can. Paint brushes or rollers may contaminate the primer with dust and other foreign objects from the primed surface. 
  • Don’t directly introduce water into the Kilz primer. As a general note, Kilz manufacturers do not advise thinning the primer.

Related Post: Can Kilz Be Used Outside? (Best Alternatives for Outdoor Priming)

How to Prolong the Lifespan of Kilz Primers After Use 

Want to save your extra primer? Follow these steps to preserve it after you use it:

  1. Clean all primer stains around the lid. 
  1. Place a plastic wrap in the can. Ensure the wrap touches the top of the primer. This will prevent a surface film from forming. 
  1. Is the Kilz primer half full? Transfer the leftover primer into a small paint container or mason jar so there’ll be less air inside since exposure to air can make it decay faster. You can get small paint containers at the local hardware store. 
  1. Use a rubber mallet to seal it tightly. If you’re using a plastic container, coat the edges with petroleum jelly to create an airtight, waterproof seal. 
  1. Label the lid of each container with the date of opening and the type of Kilz primer. 

Where to Store Kilz Primer

Most professionals recommend storing Kilz primers in a temperature-controlled environment, preferably at room temperature. Don’t place it in the garage or tool shed if the temperature is not regulated. You may risk freezing the primer. 

buckets and cans of paint

In addition to this, don’t place it near the boiler or oven. Excessive heat will cause the mixture to thicken and eventually dry up, rendering it useless. 

Place the primer cab on elevated surfaces, preferably wooden surfaces. Don’t leave the can on stone or concrete floors. Moisture from these floors will rust the cans and distort the product’s color. 

How Can I Discard Expired Kilz Primers?

It’s dangerous to dispose of expired Kilz primers without following regulations. There are different state laws on the proper disposal of expired paint products. 

Contact your state’s hazardous waste facility to learn the correct disposal process in your state.


Primers like Kilz Original will eventually decay and go bad. However, following the above guidelines can prolong these products’ lifespans. Doing so will save you the expensive headache of wasting product.