In looking at the Cloud Appreciation Society's website recently, I started wondering; if they can have so much fun finding clouds that resemble various objects, why can't we do that for frost patterns?

Awhile back, I posted frost that looked like an eye ("Eyes and Dry Moats" Jan. 22, 2010). Here are a few other forms:

A moose.


A tree.


A lawn rake (or hand) and a spider web.


Two bats and some ferns?


I noticed a few interesting things about the ferns in the above image. Look at the close-up below:


If you were to follow a line of crystals out one of the curves, and then take a ruler to the edges of the crystals, you will find that crystals at one end are slightly turned from crystals at the other. It's a slight effect, more easily seen in longer, curvy patterns, but it shows that when a finger of ice grew in the underlying water film, the crystal lattice actually twisted with strain as the finger curved. This was found out by experiments in the 1960s, so I was aware of this effect. But the other curious thing is that the line of crystals has two basic shapes: long but stubby ones and nearly hexagon-shaped crystals. They all have the same crystal orientation, but they look different. I hadn't noticed that effect before.


-- Jon