More things to ponder over a cup of coffee

I was sitting around yesterday without knowing what to do. At this point I usually look towards by book shelf for inspiration. I found it yesterday when I opened the pages of Jearl Walker's "The Flying Circus of Physics". A wonderful book full of problems which the author says himself, "are for fun... What I mainly want to show here is that physics is not something that has to be done in a physics building. Physics and physics problems are in the real, everyday world that we live, work, love and die in."

Here I've stated, word for word, a very curious and interesting problem(like all the others in the book). I don't have an answer, and I haven't looked it up. Thought I'd leave it as an open question for now. And, oh, I've noticed this myself too! But never payed too much attention as I'm too sleepy in the mornings while drinking coffee, and too preoccupied in the evenings. Anyway, it goes like this-

Coffee laced with polygons

If you examine a hot cup of coffee under a strong light that is incident nearly parallel to the surface of the coffee, you will find the surface laced with polygonal cells. They disappear, however, as the coffee cools. You can also destroy the cellular appearance by putting a charged rubber comb (charge it by running it through your hair) near the coffee.

Other liquids show surface designs too. James Thomson, a famous 19th century physicist, noticed the rapidly varying surface designs in a pail of hot soapy water and in strong wines. Later, the Frenchman Bernard was able to make regular patterns in oil surfaces when the oil was heated from below. His regular polygons would slowly evolve into a beautiful hexagonal, honeycomb structure. Still other fluids gave a roll-like appearance. Recently, cellular surface designs were attempted on board spacecraft while under zero gravity.

In these examples, why do rolls and polygons (especially honeycombs) form on the fluid surface? Is the same physics actually responsible for all of the examples? Why do the coffee cells disappear when there is a charged body nearby? Finally, do these several types of surface designs depend on gravity?

The above is listed under the topics- convection, surface tension, nonlinear fluid flow, stability, condensation.