Dry and wet foam

Wet and dry soap foam are different. Wet foam is made up of tightly packed round bubbles that barely touch. The layer of water between the bubbles is clearly visible. However, due to gravity, this water drains downwards. In addition, the pressure of the large bubbles causes the air particles to move from the small bubbles to the large bubbles. After a while you get a dry foam: the bubbles lie together like cells and are no longer round but shaped like a hexagon.

What foam do you find in your beer?