> I mean don't some people force-carbonate other drinks which are already
> beverages and not just water, like beer for example?

Certainly. Your problem with milk might have been too much pressure,
not letting it sit long enough, or your dispensing tubing length. Also,
milk is high in protein, which is what allows bubbles to form... so it
just may be too "foamy" for pressure...

As one poster said, you can force carb beer by using extra high pressure
(40#) and shaking, then reducing the pressure to serve. Also you can
just let it sit under low pressure (10#) for a couple weeks for the same
result.

I'm going to read the articles about bubble size, but the beer homebrewing
groups tend to believe that CO2 is CO2 and that any difference in bubble
size is due to other factors ... carbonation level, time, etc. (natural
carbonation takes longer). I'm curious what those articles say...

Derric