Depending on just how nitpicky you want to be, mercury is arguably the only metal that is a liquid at room temperature and unlike contenders cesium and gallium it most certainly is the only metal that stays liquid even in the type of room whose heating fails in the middle of a Minnesota winter. In fact, mercury’s most notable role through the last three centuries has been its use in thermometers as it reliably marks the hottest summer peaks and all but the coldest of polar winters. In this last use it, of course, has over the past couple of decades all but become as commonplace as phone booths for reasons of safety (at least insofar as public perceptions are concerned).

But therein lies the problem. Unless you happen to live in Siberia or Alaska the chances of it being cold enough for mercury to freeze (at around 38° below) your cube collection is never going to be complete. Worry ye not! Thanks to the amazing properties of nature we can fake our way through this little inconvenience by injecting the metal into a plastic container and sticking a cheap sticker on top and whoaa, heyyy, we’ve a mercury cube now! While we were initially skeptic they easily exceeded expectations as they look and feel great in hand.

Ps. disclaimer time: these cubes are, in case it needs to be spelled out, meant as scientific collectibles. The lids are glued shut to prevent leakage or noxious vapors from escaping but will probably not survive a fall onto a concrete floor nor present much of a challenge to a kid with a hammer. The mercury within poses no harm to you or anyone else so long as it stays inside the box. Breaking it out on purpose to play with the same way bored kids used to do with those old thermometers back in the 1970’s is a really really really bad idea. Cut ‘em a little slack… they didn’t have Xbox or TikTok, you know? So unless you’re 100% confident that you can keep this one away from the more buttered-fingered or mischievous members of your family then we seriously urge you to be okay with not filling this hole in your set.

New as of May 2024: we are discontinuing the old glued boxes filled with mercury and switching over to sealed glass. More expensive but a whole lot more elegant!