Engineering design students have struck another blow against idiom by successfully flying a lead balloon.

They responded to a challenge by British TV’s The One Show, which last year asked chocolate producers Nestle to make a chocolate teapot, based around the idiom that such a receptacle is the epitome of uselessness. In fact it proved possible to build a teapot that could hold boiling water for two minutes and then pour a drinkable, if slightly chocolaty, cup of tea. It turned out that by using dark chocolate with 65 percent cocoa solids and making the pot thick enough, the inner layer of the pot melting actually prevented further damage by acting as insulation.

The show followed up by asking students at the University of Bristol to produce and fly a lead balloon, something that is normally a metaphor for an idea sinking or going down badly.

Producing the balloon involved two main elements. The first was using a lead foil that was a mere 0.0016mm thick, though still weighed six times as much as the equivalent amount of “regular foil” (which likely refers to aluminum foil used for food.)

The second element was shaping this into a working balloon. An initial attempt using a wooden frame to put it into an ovoid shape proved too heavy. (It’s possible the students knew this ahead of time but couldn’t resist the wordplay of calling it a lead Zeppelin.)

Instead they turned to origami and overlaid the lead sheets on one another to join them in a specific flat pattern on the ground. They then used air to start the inflation before switching to helium. The origami design meant that as the balloon inflated, it twisted 90 degrees and wound up as a 1.6 meter cube.

The balloon, while kept indoors and tethered, successfully floated to five meters off the ground where it kept its position.