On 18/07/2016 12:57, 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?

Washing? We did that once to a garlic press which turned out to be
aluminium. Scrubbing it with a pan scourer removed the worst (so the
garlic came through white). Then 6 months or so of hand washes got it
back to something approaching its old self - which was admittedly
already old and tired.

--
Robin
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