Originally Posted by Jumbo82
Re-usable? I've never heard that before. Link?
The widget is just a small piece of plastic with tiny holes. The widget is full of beer, the same beer that is in the bottle. When you open a bottle of beer you release the head pressure, and the CO2 comes out of solution. When the CO2 inside the inside the widget comes out of solution, the beer is forced out of the small holes, and produces the frothy Guinness head.
If you don't believe me try this full size demo.
1. Open a beer bottle
2. Firmly place your thumb over the top and give it a shake
3. Release your thumb ever so slightly to simulate the small holes in the widget
4. Enjoy your shower of froth