Soap scum is created when soap reacts with minerals in hard water. This leaves behind a filmy substance that can make glasses and dishes appear cloudy and dull. Soft water systems combat soap scum build up. But if the soft water system breaks down, dishes can begin to turn cloudy with a scummy film. Running the dishes through a regular cycle of the dishwasher won't remove the soap scum. There are other steps that must be taken.
Use white vinegar. Fill the sink up with hot water and add ½ cup of white vinegar. Soak the dishes in the water, until the soap scum dissolves. Increase vinegar-to-water solution up to half water and half white vinegar, for stubborn stains. Rinse with clean water and dry.
Use lemon juice instead of white vinegar. If white vinegar is not available, lemon juice can also be used as an acid cleaner.
Try cleaning products that are acid cleaners, such as those containing oxalic acid, phosphoric acid, sulfuric acid or hydrochloric acid. Carefully read the manufacturers label to avoid damaging the surface of the dishes.
Soak dishes in a solution of water and bleach, which can help to remove soapy scum buildup. Be careful not to splash the bleach on clothing or fabric.