At the 2016 New Zealand Homebrew Conference, I gave a talk on beer foam. Here’s that material, reworked into an article.
Why would anyone give a talk (or write about) beer foam? Besides the fact that I find foam interesting, there are a couple reasons. When we are served a beer, our first impression is visual — we notice the color, clarity, and the character of the foam in the glass. Secondly, and more importantly, good foam is a partial indicator of beer quality. As we will see, a number of things need to go correctly to get a nice foam stand. So, the presence of nice foam indicates the brewer has (at a minimum) taken sufficient care with his or her process to produce that foam.