Kitchenaid Dishwasher Black Sludge. A water chemical reaction with certain types of glassware. Once it begins to agitate, open the lid to make it stop.
A quick fix is to paint the exposed area with vinyl paint made for dishwasher racks. And, when the racks start to rust, that rust could flake off and end up in the pump. Moldy black crud in my dishwasher.
Then, spread some baking soda over the bottom and leave it overnight.
Simply slide it along the rails until it comes free. The sludge found in the corners and drain of your dishwasher can be black or brown but always comes back to the same thing. How to naturally clean a dishwasher, straight from the appliance repairman’s mouth. Examine the drain hose for clogs.