The base of the liquid-holding portion of this stein has a small hole through which gas and liquid can flow each way. Under the hole is a container containing a piece of dry ice. It also has a device capable of grinding off a small amount of dry ice. Every time the cup is tipped a tiny amount of dry ice is ground, the hole is freed of water ice, and the CO2 is permitted into the stein where it will assure a consistent amount of head on one's beer. (or keep your soda perky)-- Voice, Mar 13 2022 (+) for the concept but... if the CO2 is not pressurized will it not just instantly bubble up upon release and sublimate a fog spilling over the lip of the stein?-- 2 fries shy of a happy meal, Mar 13 2022 A fog spilling over the lip of the stein is surely much better than plain old froth. That would be a proper mad scientist drink.-- pertinax, Mar 13 2022 random, halfbakery