Klean-Strip Paint Thinner effectively thins oil-based paint, stain and varnish. It can also be used to clean brushes and equipment immediately after use. Not intended for sale or use in California. Klean-Strip solvents and thinners are mixed into wet paint, varnish, stain and other finishes to weaken consistency and thin them out. They're also great for clean up. Klean-Strip products are like elbow grease in a can. They're formulated for professional use to strip years of old paint, clean up heavy-duty spills, and give homes a second chance.