It felt dirty writing that title…..Beer foam or head (for those even dirtier) is the result of the carbon dioxide bubbles rising to the top of the glass, and bringing with it the wort, hops and yeast residue from the brew.
The importance of this action is that the taste and smell are enhanced and it facilitates the aroma of the beer to rise with it.
Generally the density of the brew informs the thickness and longevity of the foam. This is assuming you have a clean drinking vessel of course. Dirty glassware can produce no foam or (if there are foreign bodies stuck to the inside of it) too much foam. Contamination is no joke, folks.
Apart from looking aesthetically pleasing there are many benefits for having a head on your beverage but opinion on exactly how much foam changes country to country and style to style. In places like Japan and the Philippines it’s customery to give a good bit of foam whereas in the UK we feel like we’re getting shortchanged some of our pint. Australia currently holds the record for “DON’T YOU BLOODY DARE” when it comes to headless beers.