That's a common question. Non-toxic and eco-friendly, the XSORB Rock Solid Paint Hardener is the best option for quick, easy and safe cleanup and disposal of all latex and acrylic paints. Landfills won't accept paint in liquid form. The answer to leftover paint is to use a paint hardener or solidifier like Rock Solid. Just add to leftover paint and shake or stir and watch as paint thickens into a disposable solid within minutes. Please check with local authorities for proper disposal guidelines.