When you have to store latex paint during colder months, freezing can become an issue. This is particularly bad because as the water in the paint freezes, the whole substance can turn thick and grainy, making it completely unusable. However, if you catch the freezing early enough, all hope is not lost. Here are some steps you can take to see if it is salvageable.
Step 1 - Stop Freezing With Proper Storage
Prevention is always the best and easiest remedy. Instead of storing your latex paint in a place where freezing can be a problem, make sure you keep it in a dry, temperature-controlled environment such as a basement (on a shelf) or at the bottom of a closet. Avoid places with high moisture, as the metal in the can will rust around the lid. Also, avoid places that might get too warm; high temperatures can destroy water-based paint just as easily as low ones can.
Step 2 - Defrost
For starters, your frozen paint needs to thaw. Lay newspaper on a flat surface and then set the can on top. Let it sit out at room temperature for several hours until the ice has had a chance to melt. Do not attempt to speed up the process by adding heat; this will only make any problems worse.
Step 3 - Stir
Next, you need to stir it. Pop open the paint can, and quickly check the color to make sure that the freezing temperatures have not altered it. You also need to check the consistency. If it hasn't been frozen for too long, your color and consistency may be fine.
Step 4 - Filter out the Grain
If you have noticed that your color is fine, but that the paint appears thick and grainy, you may be done for. In your best-case scenario, your consistency will be smooth upon stirring, as a cottage cheese-like texture almost always means that the paint is worthless. However, if the paint isn't too thick and the grains are few and far between, you can sift them out and use the rest.
Set a sifter bowl inside or on top of a container (something you obviously don't mind getting paint on) and pour the paint through it. The bowl should catch all the grainy pieces, leaving behind that ideal smooth consistency you're looking for.
In the event that your attempts to restore your paint have been unsuccessful, make sure you dispose of it properly. Check your local household hazardous waste laws for direction on what to do.