Allow the paint to dry by finding an area which is protected from children, pets and rain, but has adequate air flow. A locked screened porch, high shelf in a ventilated garage or shed may be suitable.
Remove the lid and allow liquids to evaporate. Depending on the type and quantity of paint, the drying process can take several days to several months. This works well for small quantities (an inch or two in the bottom of the can), but larger quantities of paint take longer to dry and may require a different method.
To speed up the drying process, partial cans can be solidified in the original containers by simply mixing equal amounts of an absorbent material, such as cat litter, sawdust, plaster of Paris, vermiculite or charcoal and allow it to dry. Excess paint can also be spread thin over cardboard or newspaper to speed the drying process.
When thoroughly dry, the remaining hardened material can be discarded with your regular trash. Leave the lid off the can so your garbage hauler can see the paint has hardened. In this form, the material is stable and less likely to cause contaminated groundwater.
Do not do the following to dispose of latex paint:
Do not dump it on the ground or down storm drains.
Do not pour it down the drain. While small amounts of latex paint can be safely washed down the drain to a septic system or wastewater treatment plant, this practice should be kept to a minimum. Limit this to brush cleaning and clean-up.
Do not throw liquid paint in your trash. It may be released from the can when trash is compacted and may seep out of a landfill, contaminating groundwater.