To answer this question first we need to discuss what makesbeerfizzy and how a forefront forms .
Most beer are carbonate with carbon dioxide ( CO2 ) . When the beer is in the can some of this CO2is dissolved in the beer and some is at the top of the can . The CO2that is dissolved in the beer is what make it fizzy . When the can is closed the insistency inside is higher than the pressure level outside , so that when you open up the can the sudden drop in pressure and the agitation of pouring causes some of the CO2to bubble out of solution , form a foreland on your beer .
A stout like Guinness has a creamy , longer lasting head teacher than a tin laager beer . In addition , Guinness is less fizzy than a regular lager beer . Guinness is canned with a mixed bag of carbon dioxide and nitrogen . Nitrogen is not take in into the beer nigh as well as carbon paper dioxide , so even though a can of Guinness may be at the same pressure as a can of lager , it contains less CO ( and is therefore less fizzing ) because the nitrogen constitute up some of the pressure sensation .
Because a beer like Guinness contains less dissolved CO2 , if you poured it from a can with no widget , the head not be very thick because most of the CO2would stay dissolve .
The purpose of the widget is to release the CO2from some of the beer in the can to create the head . The widget is a plastic , N - filled sphere with a tiny yap in it . The area is added to the can before the can is seal . It float in the beer , with the hole just more or less below the open of the beer .
Just before the can is sealed a pocket-sized stroke of liquid nitrogen is added to the beer . This liquid nitrogen evaporates during the rest of the canning appendage and pressurizes the can . As the pressure increases in the can , beer is tardily forced into the sphere through the gob , squeeze the nitrogen inside the empyrean .
When you open up the can , the press deep down immediately drops , the compressed gas inside the area quickly forces the beer out through the tiny hole into the can . As the beer pelt along through the tiny golf hole , this agitation causes the CO2that is dissolved in the beer to form flyspeck bubbles that rise up to the surface of the beer . These bubbles serve constitute the head .
