"Karl S." <null_dev@earthlink.net> wrote in message
news:pan.2004.03.22.06.32.52.734570@earthlink.net...[color=blue]
>
> I thought they'd figured that out years ago? Something about the rising
> bubbles in the middle of the glass creating an upward current in the beer
> which then flows back down around the sides of the glass, carrying some
> of the smaller bubbles down with it...?
>
> By the way, I've only seen that effect in Guinness. Is it something that
> is only visible in stouts? I'm still newbie level here...[/color]

I imagine this works for all nitrogenated beers such as Guinness and
Caffrey's. The way I picture it is that as the bubbles break near the top,
the "unbubbled" beer needs someplace to go, and that is down. Then because
the N2 bubbles are smaller then regular CO2 bubbles, they are more tightly
packed together, and are more easily pushed down when the beer falls. This
may also work in reverse, that is, as the bubbles form near the bottom of
the glass and begin to rise, the N2 bubbles are packed so tightly together
that they carry some beer along with them toward the top of the glass.
That, at least, is my theory. Need more tests.

--
Dave
"Just a drink, a little drink, and I'll be feeling GOOooOOooOOooD!" --
Genesis, 1973-ish