Whether you’re painting your bedroom or adorning an Airstream, all too often we finish up a renovation project and find we have more paint than expected. If you’re thinking you must be the only one poorly judging how much paint you need, you definitely aren’t alone. The federal government estimates that over 750 million gallons of architectural paint go unused every year, equal to 10% of what’s sold.
If (or rather, when) you end up with leftover paint, you can still put it to good use through small DIY home projects or touch-ups before it needs to be disposed of. But how long should you expect it to still be usable?
Water-based and single-component solvent paints should last between three to five years, according to Christina Rozwadowski, Rust-Oleum’s architectural coatings director.
Keim Mineral Coatings of America advertises that its mineral paints last for up to a year from the purchase date, Perri Robinson, one of the company’s regional managers, explains. However, his team has seen mineral paints that were “properly stored and performed to its full capabilities for about five years, but it’s very difficult to keep paint stored in a conditioned space for that period of time,” he adds.
If not stored properly, all that product essentially goes to waste, as it can either be completely unusable or simply won’t perform as intended. Here are some tips for making sure that your leftover paint stays stunning between projects.
Don’t let your paint freeze or get too hot
Though earlier paints might have been more resistant to freezing, Frank Glowacki, Rust-Oleum’s director of product management for paints and primers, says current regulations limit the amount of volatile organic compounds that can be in paint, making stored paints more susceptible to cold temperatures.
“If you live in Wisconsin, like myself, it’s not a real good idea to keep your half-gallon or a third of a gallon of paint out in your garage,” Glowacki says. He noted that he would be more concerned with too-cold storage versus too-hot.
Robinson notes that unlike other types of paints that could perhaps be used but wouldn’t be as effective, mineral paints are refined in a way that “once that chemical change happens, as far as going from a liquid to a solid, [the mineral paint] is no longer valid,” even if it was a short-lived or temporary freeze. “There’s no shortening of lifespan, it’s just not gonna be recreating a chemical bond to adhere to surfaces,” he explains.
Your best bet for any paint is to find a dry, temperate location to store paint, where the temperature is consistently in the range of 60 to 80 degrees Fahrenheit, Rozwadowski suggests.
Wait to pop your top
When a paint can hasn’t been opened yet, “It’s going to be the easiest to store because you know that it’s got that nice airtight seal,” Dion-Dean says. “Once the air is missing, that’s going to turn the ingredients and the chemicals inside.” Hold off until you actually want to use the paint.
Minimize air and sun exposure
Oxygen breaks down paint, so keep as much of it out of your stored paint cans as possible. Even if you’ve already opened a can, you can still preserve the paint for months or even years if you can cover it again to minimize air exposure during storage.
To get a good seal, Dion-Dean recommends wiping the paint can rim before putting the lid back on, “because once that dries it can start to push up the lid and then that can let air get into the tin itself.”
Paints should also be kept out of direct sunlight, as that can also break down the formulation.
Consider decanting to a smaller container
The less space in a closed paint can, the less air that will be left in it. If you have a suitable container at home or don’t mind buying a metal paint can from the hardware store, decanting your leftover paint into it could help minimize air exposure.
“Our labs do exactly that because we keep retains [i.e., small portions] of all of our batches,” Glowacki explains. “We don’t keep big 55-gallon drum retains of our batches, we keep them small.”
It’s easier to worry about all the things we don’t want to drip paint onto than the tiny things that could fall into the paint itself. But preventing contaminants from mixing with your paint will help it last longer and maintain its qualities.
Dion-Dean suggests that “if you were worried there’s some lumps and pieces inside, you can run it through a paint sieve and make sure all the paint that’s coming through is clear and free of contaminants.”
You probably can’t remove liquid contamination. Smaller physical contaminants, like dust, shouldn’t affect the paint if you stir it well. But any large bits—say, cat fur—should be removed to maintain appearance and texture.
“Even something the size of an ant is still going to be large because once it’s on the wall, it’s going to show a physical defect,” he advises.