Why even bother with this step in the painting process, you ask? You want to avoid opening a paint can unless you plan to use it immediately. Every time you pop that lid, you let air into the interior. Paint manufacturers craft a careful balance of pigments, binders, and additives with liquids (water, oil, and solvents) in each can — that’s what keeps the paint … paintable. Anytime you break the seal on a paint can and let air in, you risk disrupting that careful chemical balance, allowing evaporation and drying the paint out. Worse, you could even end up with mold in your paint can. Plus, the only tools you need for this hack are the brush, paint, and can you’re already using.
Store your paint cans with the stripe of paint facing out. That way, you can assess at a glance how much and what kind of paint a can contains whenever you open your storage cupboard or need a particular paint hue or type. Store them right-side-up, too. Not only will the stripe of paint show what’s left in the can correctly, but the commonly held belief you should store used paint cans upside down for a better seal is a myth. It’s more likely to cause leakage than preserve your paint. A better choice is fitting a piece of aluminum foil over the lid.