Grayish Residue on Beater or in Food
The shiny silver colored burnished aluminum beaters are not dishwasher safe.
If washed in the dishwasher or allowed to soak in the sink, the burnished aluminum finish may start to oxidize and form a grayish residue. This grayish residue is not harmful, but it may discolor food items mixed in the bowl.
Burnished beaters should be hand washed and towel-dried immediately. Do not allow them to air dry. If you prefer to put your beater in the dishwasher, KitchenAid offers white-coated beaters for all models, which are dishwasher safe.