Any person who does home renovation will have old paint lying around or buying new cans that have never been opened.
If you are in this situation and have old paint or full cans in your shed, you may wonder how long does paint last before you need to think about disposal.
The paint’s chemical makeup (chalk paint, latex paint, milk paint, or oil-based paint differ) will determine how long paint can last before opening and once you have opened the can.
You’ll also find opened cans differ from cans that are sealed. Even fully sealed contents of an unopened can that is tightly sealed have an expected life duration, especially if they are repeatedly frozen in your shed from extreme temperatures.
In our guide, you can learn more about how long paint lasts, a paint cans shelf life, and by the end, you’ll know how long does paint last before it isn’t any use for that new paint job. (Learn How To Get Spray Paint Off Concrete)
How Long is Paint Good For After Opening?
Here you can find estimates of how long does paint stay good and an overview of each paint type.
- Latex or Acrylic-Latex Paint 2 to 10 years
- Acrylic Paint 2 to 15 years
- Oil-Based Paint 2 to 15 years
- Chalk Paint 1 to 5 years
- Milk Paint: Mixed in Can 1 – 2 years
- Milk Paint 1 to 7 days when mixed from powder
Latex Paint
Water-based Latex paints are versatile water-based paint for interior and exterior use. Latex paint contains fewer toxins than oil-based paint because it is mostly water. It is, however, more prone to freezing. Latex paint can last between two and ten years if stored properly.
If you live in a cold climate, avoid storing latex paint in an unheated garage or shed as regular freezing and thaw cycles cause your paint to be full of grainy lumps.
Minor lumps can be gently stirred out with a paint stick, or you can pass it through a paint strainer; however, if the problem is severe, you won’t be able to paint your walls evenly. (Find the Best Waterproof Latex Paint)
Oil-Based Acrylic Paint
Oil-based paint is a good paint as it spreads easily on any surface, yet it contains more volatile organic compounds (VOCs) than water-based alternatives. Since the paint is oil-based, it is much more likely to separate compared to water-based acrylic paints.
Old paint has the longest shelf life after unopened cans when stored correctly and sealed in a container. Even if the can has been opened, you can take measures to help the paint last for up to 15 years.
A simple piece of plastic wrap covering the paint can stop skin from forming on any paint. When oil-based paint is left partially opened, it dries quickly. To seal a can and prevent any semi-solids, you can seal the lid with a rubber mallet.
If your oil-based paint has gone bad, or it looks that way, a stir will have it back to normal in no time. Use a permanent marker to write which other projects you used the paint and when.
Chalk Paint
Chalk paint is perfect for minor furniture or doors since it is super thick and smooth. It dries to a stunning matte surface that may be layered, scuffed, or sanded for a modern aesthetic.
While chalk paint can survive for up to five years if properly maintained, it will dry up significantly faster if exposed to the air. If your chalk paint has thickened significantly since you used it, know that you can thin it with water and use it again.
Milk Paint
Milk paint is the paint with the shortest shelf life of all. This thick paint is free of any dangerous compounds and is excellent for projects involving children. Although mixed, this form of paint has a shelf life of up to a week because of the milk proteins.
Does Unused Paint Go Bad?
If you wonder how long does paint last, paint companies such as Sherwin Williams estimate that the paint shelf life is typically modest. Some paint manufacturers estimate a two-year shelf life for unopened cans of latex paint, while others estimate one-year shelf life.
For the most common, you may ask, how long does latex paint last? Interior latex paint has a shelf life of several years, according to most manufacturers. However, paint and home renovation experts agree that well-looked after latex paint has a shelf life of up to ten years.
When stored properly, unopened paint cans endure for years. Unused latex and water-based paint can last up to ten years, whereas alkyd and oil-based paints can last fifteen years.
New latex or oil paint cans that have never been opened last three years on average. It can survive for years if you store unused paint properly and don’t expose it to air.
If the paint is oil-based, it may not dry, and if it is latex, the color pigment may not be consistent throughout the mix, resulting in patchiness. There are a few ways to tell if the paint is bad, and it varies based on paint type. (Learn When To Remove Painters Tape)
Regardless of how long your paint lasts, here are the ways to tell if your leftover paint has gone bad or you need to take a trip to the paint store for a new can.
Bad Smelling Paint: Some paint left in a can may smell rancid or sour after opening the lid. Other paints may have a smell of mold. The reason for this is that as paint becomes bad, bacterial growth occurs, and while the paint may still work, the smell may not vanish when you apply a fresh coat of smelling old paints.
Fluctuating Temperatures: You won’t want to store paint where it can be contaminated or exposed to temperature extremes in many circumstances. If you use water-based paints, such temperature swings might be damaging.
Even though you can thaw paint from a freezing temperature, if paint freezes repeatedly, the paint breaks down.
Likewise, extreme heat can also have an impact as it can dry water-based paints and solidify latex paints. (You can solidify latex with cat litter for disposal in some states).
Lumpy Paint: After some time, latex paint develops a film or skin on the top. If your paint solidifies beneath the skin, you may need to toss it. Water alone will not dissolve solid paint.
Here are some quick steps you can follow to revive your oil-based paint before disposing of it.
- Place the open paint can on a plastic sheet or newspaper.
- Add 1 oz. of paint thinner to the paint can. You may have to add more or less based on the amount of paint and the thickened skin in the can.
- Stir paint thinner in the dried paint with a paint stirrer or clean stick until the paint thickens.
- Add 1/2 oz. or 1 oz. of the paint thinner and stir well to incorporate.
- Add more paint thinner in 1/2 oz increments until you have thinned the dried paint and reached the desired consistency. Test on cardboard before you use it on walls and doors.
- Thinners can leave a foul odor, so do this in a well-ventilated area such as your garage rather than in the house.
