I read this tip somewhere. When you empty a plastic container that has tomato sauce in it..pour Dawn or any dish detergent in and use a paper towel to wipe down before you use any water. I wipe the container with a dry paper towel first then add detergent then wipe again Let sit for a while then wash. Works on my splatter lit that I use in microwave too. For some reason if you use water first it doesn't work.