Perhaps spring cleaning led you to the discovery of a bunch of half-full paint cans in the garage. Or maybe you're moving and need a way to get rid of extra paint without having to haul it to a new house. You certainly can't pour extra paint down the drain, and leaving it for the garbage collectors to pick up can harm the environment. You can purchase paint hardeners at hardware stores that turn the paint into a solid form and make it safe for disposal. However, you can also make your own paint hardener at home.
Spread sheets of newspaper on the ground and line up your cans of paint on top of them. Pry open the lids of all of the cans of paint you wish to dispose of. Set the lids of the paint cans aside. Any residual paint on the lids will dry on its own in a day or two.
Scoop the cat litter into the cans of paint. The proper ratio is one part cat litter to two parts paint. This doesn't have to be exact and you can estimate the amount of kitty litter needed. Use a paint stirrer to mix the litter into the paint. Repeat this step for all cans of paint you wish to dispose of.
Allow the cans of paint to sit for at least two days in a well-ventilated area. Do not replace the lids. Over the next couple of days, the cat litter will remove the moisture from the paint, turning it into a solid.
Dispose of the cans and lids with your regular trash.
Do this project in a well-ventilated area to avoid fumes and to allow the paint to dry faster.