Sorry if I inferred 'no substances of any kind'. Those such as alchohol that go away or evaporate should be fine.
Added note- You can clean disc pads on the flat with fine grade sandpaper, don't overdo it. Mechanics in Moab showed this to me when I wanted to get rid of squeal.
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"I tell you, We are here on earth to fart around, and don't let anybody tell you any different." - Kurt Vonnegut jr.