A drop of air held by water is the twin of a drop of water held by air. They are both thickenings in the sense of words forming from breath. In foam, a spray does not radiate but is held to its central form by the tension of a surrounding liquid, in the same way that the surface tension of draining water holds to its form as a drop. Foam is a slow energy, a surface that develops thickness to form a whole. Poetry is a form of foam.
Frozen foam in a winter run of water.