Sub-Zero Bubble Discussion

Your votes have been tallied in the poll about the behavior of sub-zero bubbles (see previous post).

22 Warm Risers
25 Milky Spheres
46 No Difference
40 "Plastic" Shreds
24 Crystal Globes

I believe the best answer is "plastic shreds," as many of you with direct experience also attested. The other answers made either poetic or logical sense, but they don't match my own observations so far.

However, the answers aren't cut and dry, as you'll see in the videos and photos. There should be some healthy debate. We have may have discovered a Gap in Human Knowledge.

We can safely rule out "no difference" and "warm risers." I would argue that warm air doesn't lift bubbles higher because the air cools very quickly, and also the elastic walls of the bubble instantly expand to keep the pressure gradient constant. In other words, the air in the bubble can't stay less dense than the surrounding air long enough to lift it up. Soap bubbles are always heavier than air; bubbles only rise with air currents.

The descriptions involving hard frozen spheres in #2 and #5 are pure invention and wishful thinking. I'm not a chemist, but my understanding is that the glycerin which helps form the bubble membrane also interferes with the formation of the molecular latticework needed for hard crystalline freezing. If there was a way to produce a bubble with some other chemical additive, a hard-frozen bubble might be possible.

Can bubbles hold a shape or give the appearance of being frozen? Here's a video, which clearly shows frozen bubbles rolling on a carpet, making it impossible to rule out the hard-frozen globe choices. My impression, though, is that the bubbles are still a bit leathery and not hard like ice or glass.



The solid freezing argument also seems to be supported by this YouTube video, but it's a bit inconclusive:


What happens when the bubble pops? For reference, here's what a soap bubble does when it pops at room temperature. The aperature opens around the sphere in a moving front of scattering droplets:



In very cold temperatures, the popping behavior is unexpected. Like a tired "day-after-the-birthday-party" latex balloon, the action is often slow enough to be observable.

In temperatures of -25 Fahrenheit, the bubble rips open and sometimes stays together, falling delicately like a torn gray bag. At 15 below, it breaks up into floating ash-like shreds, looking like fairies, as Amanda remembered from her childhood in northern Illinois.

Finally, here's a great link with really gorgeous still photos.

They say it will get to a few degrees below zero this Sunday. Those of us in the Frozen North, get your bubble stuff and cameras ready!