We start with 112 dishes and pieces of flatware. We make sure they're all perfectly clean and dry, so the only dirt on them when we load them into the dishwasher will be the dirt we put there. Then, we collect our foods. Our mix of foods is selected to test the different capabilities of a dishwasher. Honey, egg and peanut butter task it with removing sticky substances. Spinach and macaroni and cheese see how well its filter deals with bulk.
Then, it's time to run the dishwasher. For our tests, we use the normal cycle with no add-ons, because other cycles vary wildly from dishwasher to dishwasher, and we want to compare apples-to-apples results.
Once the dishwasher cycle finishes, we allow the machine to rest for 30 minutes. We're grading it on both cleanliness and dryness of dishes, and we give it a chance to help itself on the latter with residual heat.
After the 30-minute timer sounds, we remove the dishes one by one, and inspect them under a 4-foot LED array set to a specific color temperature. We look for any drops of water or water marks, as well as any remaining spots of food.
We grade the dishes based on the number and size of food spots and water spots we find, giving a separate numerical score for cleanliness and dryness for each dish. We plug those scores into an equation and get a total percent dry and clean score for the dishwasher.