As I wrote about a month ago, one of the many unusual phenomena Ben Krasnow has produced in his garage is supercritical CO₂. As you may recall, Ben machined a custom acrylic pressure vessel so he could get (and give) a good look at a state of matter that most of us have little experience of. Since then Ben has inadvertently had a chance to observe another extremely unusual effect: the carbonation of solid acrylic.

After completing his observations, Ben cooled the pressure chamber down, condensing the supercritical CO₂ back into a liquid state at about 750 psi. Then he left it for a week before disassembly. At some point in the process, the hypothesis goes, the high-pressure carbon dioxide diffused into and/or dissolved (the precise term is debatable) the solid acrylic. Once pressure was relieved, it slowly (over the course of several hours) defused back out into the atmosphere, causing the crazing, bubbling, and swelling shown in Ben’s video. Like opening a bottle of really, really, really viscous soda pop. [Thanks, Ben!]