When you have leftover paint from a previous project, it can be tempting to use it for your next painting job to save money. But how do you know if old paint is still usable? There are a few simple tests you can conduct to find out if that old can of paint is still good or if it’s time to invest in a fresh batch.
Check the Consistency
The first thing to look at when evaluating old paint is its consistency. Take a paint stirrer or popsicle stick and dip it into the can, stirring the paint around a bit. Fresh paint should have a smooth, creamy texture. If the old paint has become thick, lumpy, separated or has pieces floating in it, then it’s well past its prime.
Paint hardens over time as moisture evaporates and the solids separate from the liquid components. This hardening causes the texture to change from smooth and creamy to thick and clumpy. So pay close attention to the paint’s consistency right off the bat when initially stirring it.
Examine the Color
Check if the color of the old paint still looks normal. Over time, paint color can start to change for a couple reasons. First, the pigments that provide color can start to separate and settle at the bottom of the can. Stir the paint and see if the color looks uneven throughout the can.
Second, if improperly stored and exposed to sunlight, paint colors can start to fade over years of storage. Compare the color on the lid label to the paint in the can. If the paint is noticeably lighter or a different hue, then it’s time to replace it.
Smell the Paint
A bad smell is a definite indication that paint has gone bad. Fresh paint has a fairly neutral odor. As paint ages and goes bad, you may notice a strong chemical smell or an almost rancid, rotten odor.
This change in odor occurs as the solvents and binders in the paint break down over time. Once you get a whiff of old, smelly paint, it’s not advisable to use it.
Check How Full the Can Is
A mostly full can of old paint has a better chance of still being usable compared to paint cans that were left partially filled after a project. Exposure to oxygen is one of the main reasons paint goes bad. When a can is less than half full, it has a lot more airspace where oxidation can occur.
Before opening a can, first check the weight by lifting it. If the can feels less than half full, be extra suspicious of the paint’s quality before doing an opening test.
Do an Opening Test
If the paint passes the initial consistency, color, smell and fill-level inspections, the next step is to open the can and evaluate the opened paint. Use a flat tool to pry open the lid. If the lid is stuck on tight, that’s actually a good sign the can was well sealed.
Once open, check that the paint still looks and smells normal. Also check for a plastic film on top of the paint. Over time oils can leach out of latex paint, forming a skin on top that needs to be peeled away. If the film is thin, the paint should be fine after removing it.
However if the paint has formed a thick film or skin over 50% of the can’s surface, this indicates destabilization and the latex binders have likely broken down too much for the paint to still be usable.
Do a Patch Test
The final determiner of whether old paint is still usable is to test it out on a patch of wall. Pour a small amount into a paint tray and use a roller or brush to apply it to a section of primed drywall, concrete, brick or other surface that matches what you’ll be painting. Allow the paint to dry completely (at least 24 hours).
Check the coverage and color of the paint. See if it dried to a normal-looking matte or glossy finish without issues like cracking, forming lumps or becoming tacky/sticky. If the patch test paint flowed on well and dried to an even, opaque coating that looks good, then the old paint is likely fine to use!
How to Store Paint Properly
To get the longest life span out of leftover paint, it’s important to store it correctly. Here are some tips for proper paint can storage:
- Pour excess paint back into the can and seal the lid tightly after use. Try to minimize air space.
- Store paint cans upside down if possible. This prevents air bubbles from forming in the paint over time which can lead to oxidation and drying.
- Place lids tightly on spray paint cans and store them nozzle side up to avoid clogs.
- Keep paint cans in a temperature stable location away from external walls or drafty spaces.
- Avoid freezing paint or storing paint somewhere it could boil, like a hot garage or shed.
- Keep paint out of direct sunlight which can cause fading and affect longterm quality.
Following these storage methods can add years to a can of paint’s shelf life. Just be sure to still do the opening tests described above before using very old paint for an important project.
How to Tell if Latex vs. Oil Paint Has Gone Bad
The tests for checking if old paint is still usable apply to both latex (water-based) and oil-based paints. However, there are a few differences to be aware of when evaluating the quality of each specific paint type over time.
Latex Paint
Latex paints last around 5 years if properly stored, and up to 10 years before they begin deteriorating. Signs old latex paint is no longer usable include:
- Visible mold/mildew in the can or a foul spoiled milk smell
- Separation that doesn’t mix back in with stirring
- An extremely thick, clumpy or lumpy consistency
- Cracked or peeling when dried on a test surface
If old latex paint passes the opening tests and patch test without issues, it can likely be revived with some thinning to improve the viscosity. Add clean water gradually, stir, and test consistency on cardboard until optimal consistency is reached.
Oil-Based Paint
Compared to latex paint, oil-based paints have a longer shelf life around 7-10 years. Be on the lookout for these signs oil paint has expired:
- A greasy or slick film on top of the paint
- Changes in color, usually darker yellowish hues
- Solvent odor is very strong and irritating
- Paint doesn’t fully harden on test patch after 48 hours
Old oil paint may also feel quite stiff initially. It can be possible to extend usability by stirring in painting solvents like mineral spirits to improve viscosity. However, reanimating old oil paint runs a higher risk of having adhesion or curing problems even if thinned out.
Can Expired Paint Make You Sick?
Using paint that has spoiled or separated beyond rescue can cause problems beyond just poor coating quality. Solvent-based paints in particular can become hazardous as they degrade over time.
As the solvents break down, they can release unsafe volatile organic compounds (VOCs) and fumes that are flammable and irritating to the eyes, nose and lungs if used in a poorly ventilated indoor space.
Moldy paint is another health hazard. Breathing in mold spores as you apply old, contaminated paint can potentially lead to respiratory illness.
It’s not worth taking risks with old paint that may have potential health dangers. It’s better to properly dispose of it and simply buy new paint you can confidently use.
How to Dispose of Bad Paint
Pouring old paint down the drain or throwing it in the regular trash can cause environmental pollution. The best way to responsibly dispose of expired liquid paint is through a household hazardous waste (HHW) collection program.
Most municipalities host periodic HHW drop-off events or have permanent facilities where residents can safely dispose of chemicals like paint, stains, pesticides and other toxic household products to avoid contaminating landfills and waterways. Contact your local environmental or sanitation department to find disposal options in your area.
For small amounts of leftover hardened latex paint, removing the lid and allowing the paint to dry out completely before placing the can in the trash is also an option. Just make sure to only put paint in normal curbside trash if it’s fully dried out and solid.
Proper paint disposal is important to avoid pollution and hazards. But the best way to reduce the need for paint disposal is by only buying what you need to avoid having excess paint taking up space and going bad before use.
Frequently Asked Questions
How long does unopened paint last?
Unopened cans of latex and oil paint can last between 2-5 years if stored properly before deterioration starts. Shelf life depends on type of paint, storage conditions and quality of the paint. Higher quality paints and optimal storage can extend lifespan closer to 10 years.
Can old paint be mixed with new paint?
It’s not recommended. Mixing new and old paint together that are different colors or brands is risky. It’s better to just use the old and new paint as separate batches. Blending old paint into new paint could compromise coverage and finish quality.
Will paint still be good if frozen?
Freezing paint for extended periods causes paint to break down faster. The water in latex paint can freeze-thaw cycle, damaging binders. Oil paint also becomes more viscous. It’s best to store paint above 40°F if possible.
Can you use paint that separated?
If it’s latex paint that separates but remixes smoothly when stirred, it should be fine to still use. Oil-based paints are more problematic if separation occurs. Small separation may be fixable with solvents and mixing. But fully separated paint is best disposed of.
How do you soften old oil paint?
To soften thick, hardened oil paint, stirring in paint thinner like mineral spirits may help improve flow and brushability. Start with a 5-10% ratio of thinner to paint. Don’t thin too much as over-dilution impacts drying/curing.
Conclusion
Checking old paint before using it is an important step to ensure you don’t end up with a poor quality paint job. Testing the paint’s appearance, consistency, smell and how it applies to a surface will reveal if it’s still in good condition or past its prime.
With proper storage methods, both latex and oil-based paints can remain usable for years. But exposure to oxygen, light, cold or heat speeds up deterioration. Dried out, smelly or moldy paint should be disposed of and fresh paint purchased for best results.
