I use rum/vodka to fortify wine and make liqueurs, and I noticed
something strange when I shook a bottle of plain white rum. (The same
thing happened with vodka.) When I shook the bottle, the liquid's
appearance changed in three quick stages:

- cloudy all over (first 1-2 seconds)
- started to clear, but a thin layer (< oz.) of white foamy/starchy
substance surfaced (3-7 seconds)
- everything cleared back to normal (8-10 seconds)

I'm aware that cheap alcohol is usually not filtered as much as
top-shelf brands, so I'm suspecting the shaking caused a temporary
"centrifugal effect" that, for a short time, surfaced many of the
impurities. If I poured out the little oz. or so of the foamy liquid,
would the remaining liquor be cleaner?