It turns out that Czarist style Imperial Stouts are heavier than Ale. In fact, I'm looking at a rather enticing quart mug of Tan & Black just now. The bottom third of the mug is Stone Imperial Stout [from the makers of Arrogant Bastard Ale, in St. Marcos CA, arrogantbastard.com] while the top 2 thirds of the mug efervesces with the golden-red hues of George Killian's finest.
Gulp after gulp, the massive Imperial Stout slides back to the bottom of the mug with hardly a wisp of mixing. Like oil and water... except the oil sinks to the bottom.
This may be the coolest kitchen chemistry experiment since home-milled anthrax. Incidentally, a hand full of stainless ball bearings and a polypropelene cyclist water bottle, and you too can make a ball mill that produces sub-micron powders. It isn't rocket science... but rocket scientist and fireworks enthusiasts may have used the trick before jet mills were common.