A liquid organotin heat stabilizer for clear, opaque and/or colored calendered rigid Polyvinyl Chloride (PVC) comprising octyltin mercaptide and methyltin mercaptide. Octyltin mercaptide is used to develop good early color in a clear, opaque or colored calendered rigid PVC film application. Methyltin mercaptide is used to improve the long term heat stability (reduced burning) of the clear, opaque or colored rigid calendered PVC films. Ranges from 50% to 75% octyltin mercaptide, and from 50% to 25% methyltin mercaptide have application. Preferred ranges are 60% to 64% octyltin mercaptide and 40% to 36% methyltin mercaptide. Most preferred is 62% octyltin mercaptide and 38% methyltin mercaptide.