On 7/18/2016 12:57 PM, GB wrote:
We have a very old Kenwood mixer, with aluminium beaters. We
unfortunately put them in the dishwasher, and they are now covered in a
soft black deposit. What's the best way to get that off and if possible
restore the finish?

Wire brush, perhaps with brass rather than steel wire. A suede brush
would do, if you can still get them.