Beer foam

I saw someone pouring beer into a glass today, and noticed that a lot of foam was formed. This is because when the liquid is poured quickly into another container, carbon dioxide is released. Carbon dioxide can be formed as a by product during the making of beer.  The glass into which the beer is poured is also a factor in the formation of foam.  When the glass is nonporous, it tends to retain more oil, and when the beer comes in contact with the oil, it bubbles will then stick to the glass' surface instead of rising to the top, thus reducing the amount of beer foam.