Over time, a heavy film build-up from hard water minerals can become deposited on the inside walls and heating element of the dishwasher. After removing all of dishes, pans, silverware etc. and with no detergent in your dishwasher, the following should be done to remove the type of scale shown:

Mold: Place one tablespoon of bleach in your dishwasher and then run it for a full cycle.

Rust: Place about half of a small container of Tang brand orange-flavored drink mix and then run it for a regular cycle. The citric acid in the Tang helps to loosen hard water deposits and cleans the scale from your dishwasher.

Stains: Place a cupful of white vinegar in your dishwasher and then run it for a full cycle. An alternative to vinegar is baking soda.